text:
|Publication number
|Publication type
|Application number
|Publication date
|Jul 20, 2010
|Filing date
|Jun 30, 2006
|Priority date
|Jun 20, 2006
|Fee status
|Publication number
|Vishal Zinjuvadia
|Original Assignee
|Force 10 Networks, Inc.
|Export Citation
|BiBTeX, EndNote, RefMan
|Patent Citations (28), Non-Patent Citations (7), Referenced by (56), Classifications (15), Legal Events (3)
|External Links: USPTO, USPTO Assignment, Espacenet
This application claims priority to and is a divisional of U.S. patent application Ser. No. 11/455,948, filed Jun. 20, 2006, which is incorporated herein by reference in its entirety.
1. Field of the Invention
The present disclosure relates generally to network switching, and more particularly to an adaptive spanning tree protocol that allows multiple spanning tree instances to be dynamically modified based on selected traffic attributes.
2. Description of Related Art
Spanning Tree Protocols (STPs) are used in computer networks to maintain a reconfigurable-on-failure loop-free network topology within a group of interconnected switches having redundant paths. In the original STP specification (IEEE 802.1D, published by the Institute of Electrical and Electronic Engineers), failover and fallback of links to employ alternate paths was timer-based.
Enhancements to the core spanning tree protocol were suggested, allowing rapid convergence and recovery of the spanning tree after link failure, independent of any timer. These enhancements became known as the Rapid Spanning Tree Protocol (RSTP), described in the IEEE 802.1w specification, currently merged into the IEEE 802.1D-2004 standard.
Further enhancements to the basic spanning tree protocol were made to allow a group of switches to run multiple spanning trees instances within the same spanning tree domain. An administrator provisions each switch in the spanning tree domain with a mapping between spanning tree instances and VLANs (Virtual Local Area Networks), and tailors the bridge parameters in each switch so that different multiple spanning tree instances will converge to different least cost paths through the network. The traffic for each VLAN is forwarded along the network paths for the spanning tree instance mapped to that VLAN. With some effort, an administrator can therefore achieve better load balancing than is generally possible with a single spanning tree instance, since no operational port will necessarily be blocked in all spanning tree instances. These enhancements are described in the IEEE 802.1s standard as the "Multiple Spanning Tree Protocol" (MSTP). Currently, MSTP has been integrated into the IEEE 802.1Q-2003 standard.
Additional enhancements in the field of spanning tree design are described in U.S. patent application Ser. No. 11/065,724, entitled "Packet Attribute-Mapped Spanning Tree Protocol," filed Feb. 24, 2005, and incorporated herein by reference. The Attribute-Mapped Spanning Tree Protocol (AMSTP) can be configured to map packet attributes other than (or in addition to) VLAN identifier to logical spanning tree instances. For instance, different spanning trees can be associated with different Ethernet layer 2 header Ethertypes, layer 3 addresses or portions of addresses, layer 4 types indicated by layer 3, IP options, multicast/unicast traffic, higher-layer header attributes, data attributes for specific packet types, etc. This structure provides powerful flexibility for dividing network resources according to a wide variety of specific traffic attributes.
The present invention can be best understood by reading the specification with reference to the following Figures, in which:
Several disadvantages have now become apparent in STP, RSTP, MSTP, and AMSTP as described above. First, although spanning tree fallback topologies will be activated in each of these spanning tree protocols should one or more links go down, there are a variety of ways in which an operating spanning tree topology can become—temporarily or semi-permanently—suboptimal, without causing link failure and reconvergence of the spanning tree. The embodiments below allow dynamic reconfiguration of the spanning tree topology, e.g., in situations where link status has not changed, but some change in network hardware, traffic patterns, etc., warrants adjustment of the topology.
A brief description of a few spanning tree concepts and spanning tree terminology will now be presented as an introduction to the embodiments.
Each group switch connects via two point-to-point links to, respectively, two aggregation switches AGG-1 and AGG-2. Switch AGG-1 is connected in turn by two point-to-point links to, respectively, two core switches CORE-1 and CORE-2. Switch AGG-2 also is connected by two point-to-point data connections to CORE-1 and CORE-2. The core switches each have at least one uplink port connected to the layer 3 network 110. This configuration provides at least two redundant paths between each group switch with each other group switch and with the layer 3 network. Switches CORE-1, CORE-2, AGG-1, AGG-2, GSW-1, GSW-2, GSW-3, and GSW-4 are configured in a common spanning tree domain.
Assume first that the spanning tree protocol run by the
Through the interchange of BPDUs, the switches also learn which one, if any, of their ports will become a root port—the port that is closest to the root bridge in terms of port cost. The interchange of BPDUs also allows the switches to assign designated ports for each network segment—a designated port is defined as the port capable of sending the best BPDUs on the segment to which it is connected. Root and designated ports are shown in
The remaining ports are neither root nor designated ports. These ports are described as blocking ports and are illustrated in
One drawback of the
With MSTP and AMSTP, it is possible for switches to use different spanning trees for packets belonging to different VLANs (MSTP), or for packets with specified attributes (AMSTP).
In MSTP, each VLAN is assigned to one of 64 logical spanning tree instances (or a subset of the 64, such as the four instances shown in
Within an MSTP region, only one set of BPDUs is propagated by each switch. The BPDU format for MSTP contains a fixed first section, followed by a variable number of configuration messages, one per MST instance. The BPDU format is as follows:
Protocol Identifier Protocol Version Identifier BPDU Type CIST Flags CIST Root Identifier CIST External Path Cost CIST Regional Root Identifier CIST Port Identifier Message Age Max Age Hello Time Forward Delay Version 1 Length = 0 Version 3 Length MST Configuration Identifier CIST Internal Root Path Cost CIST Bridge Identifier CIST Remaining Hops
followed by a variable number of configuration messages of the following format:
MSTI Flags MSTI Regional Root Identifier MSTI Internal Root Path Cost MSTI Bridge Priority MSTI Port Priority MSTI Remaining Hops
The fixed first section contains information that is used to establish a Common Internal Spanning Tree (CIST) that will be used within the MSTP region as a default spanning tree for traffic not otherwise assigned, and represents the MSTP region as a virtual bridge to the outside world. Many of these fields correspond to RSTP fields used to establish an RSTP Spanning Tree. The MST configuration identifier field, however, identifies the MST group by an alphanumeric configuration name, a configuration revision number, and a digest value. Each switch calculates its MSTP digest value by hashing its VLAN-to-MSTP-instance mapping table with a known hash function, the "HMAC-MD5" algorithm described in Internet Engineering Task Force document RFC 2104. The digest value transmitted within a BPDU must match the internally-calculated digest value in order for a switch to recognize the BPDU as one originating from its MSTP region. Thus if the VLAN mapping tables for two connected switches do not match exactly, the two switches will transmit BPDUs with different digest values. Consequently, the two switches will not cooperate in a common MSTP region, and each assumes that the port on which it receives the differing digest value (or no digest value) is at the MSTP region boundary.
Assuming that the MST configuration identifier digest matches a switch's digest, the switch will participate in establishing a CIST for the region and a number of MST Instances (MSTIs) equal to the number of MSTI configuration messages. For each MSTI, the corresponding MSTI Configuration Message contains bridge and port priorities used to calculate a spanning tree for that instance. A network administrator assigns different bridge and/or port priorities in different MSTIs for at least some switches, such that the MSTIs may be designed to elect different root bridges and may block and forward on different ports to achieve a more load-balanced topology.
It can be appreciated that the complexity of the MSTP approach changes little as further VLANs are included in the MSTP instances. Efficient manual design of the spanning tree bridge and port priorities for each instance and VLAN-to-instance mapping becomes more challenging, however, as network size grows.
In the AMSTP approach, logical spanning tree instances such as the four instances shown in
Destination MAC (Medial Access Control) address
Source MAC address
Layer 3 Protocol Type ("Ethertype")
DSAP/SSAP (IEEE 802.2 Destination Service Access Point/Source Service Access Point)
Furthermore, many switches also support parsing of Layer 3 header fields when switching traffic at Layer 2, making these fields available as a spanning tree attribute. For instance, when combined with an Ethertype attribute of 0x0800, which indicates that a packet is an Internet Protocol version 4 (IPv4) packet, the following IPv4 layer 3 header fields can also be a spanning tree attribute:
In some AMSTP embodiments, a network administrator can be presented with several supported traffic attributes, from which she can select one or several that make sense for the particular network topology and switching resources. The network administrator specifies how various values of the attribute(s) are to be split among a set of spanning tree instances, and loads this association and selection of attributes to the switches that are members of the region. The switches use the attribute selection and attribute/spanning tree association to build a digest that can be used to recognize other switches in the same region. If the selected attributes (for instance some layer 3 header fields, higher-layer attributes, or data attributes) are not used already by the switch to perform CAM (Content-Addressable Memory) lookups, the switch can add these fields to the lookup key to maintain forwarding performance.
When the new configuration is propagated, the switches can then use it to calculate the network topology. The MSTP BPDU framework, modified (by at least inserting a digest calculated for AMSTP attributes) to indicate that the BPDUs are for AMSTP and not MSTP, can be used to exchange BPDUs and converge the network to a multiple spanning tree solution. The switches then use the attribute/spanning tree association provided by the network administrator to forward traffic.
The desirable attributes of the MSTP and AMSTP protocols include the ability to attain a loop-free network topology, the ability to load-balance traffic, the ability to provide an alternate topology that can be advanced should a link or node fail, and the ability to run multiple internal spanning tree instances with a single code instance and set of BPDUs. AMSTP includes enhanced flexibility in the binding of selected traffic to spanning tree instances.
In the embodiments described below, an RSTP, MSTP, or AMSTP spanning tree region can be dynamically reconfigured to respond to certain types of events. For instance, if layer 3 traffic began entering the network at a different location, one embodiment allows a network device to initiate a layer 2 realignment to better match the layer 2 topology to the new layer 3 topology. In another embodiment, changes in the resources available at a network node (short of total failure of a link) cause that node to adjust its bridge/port priority and trigger reelection of a root bridge and reconvergence of the spanning tree. In yet another embodiment, dynamic traffic mapping to spanning tree instances is used to respond to transient traffic conditions. These and other embodiments will now be described in further detail.
In a first embodiment, a switch recognizes that due to an event occurring outside of the LAN, traffic is following a suboptimal path through the LAN. Switches participating in a spanning tree initially determine their best (least cost) path towards the root switch and designate the switch port following this path as their root port. This guarantees that the traffic from the switch to the root flows via the least cost path in the Layer 2 topology. In similar fashion, Layer 3 unicast and multicast routing protocols provide the least cost Layer 3 path(s) for routed traffic. This path may span one or more autonomous systems. In a typical enterprise topology, such as the one shown in
In a prior art system, the Layer 3 routing protocol and the Layer 2 switching protocol have no awareness of each other. A network engineer would attempt to bridge the gap by configuring the Layer 2 topology in such a way as to avoid any bottlenecks between the Layer 3 entry point into the destination network and the Layer 2 topology. If for some reason external to the destination network (such as a change in routing cost) the routed traffic enters the network at a different location than that intended by the network engineer, bottlenecks and/or increased latency may follow as the traffic follows an unintended and potentially lower-capacity and/or longer path.
In this embodiment, a mechanism exists to detect misalignment between the Layer 2 and Layer 3 topologies, and then adjust the Layer 2 topology to realign it with Layer 3. For instance,
In diagram 412, the PIM Forwarder for source S has moved away from the STP Root Bridge, causing the multicast traffic received from source S to travel an inefficient path back to the STP Root Bridge and then down to the destination endpoint. As the PIM Forwarder designation may be out of the local network's control, what seems more efficient from a Layer 3 standpoint (e.g., least cost to reach source S) has resulted in inefficiency in the Layer 2 forwarding paths.
In one embodiment, one of the switches, e.g., switch 420 now hosting the PIM Forwarder, recognizes that it is receiving multicast traffic from the Layer 3 network 110, but that it is not the spanning tree protocol root bridge for that traffic (the spanning tree in question may be a single RSTP spanning tree or one of multiple spanning trees, e.g., an AMSTP spanning tree dedicated to the particular multicast traffic associated with source S). Switch 420 analyzes the root bridge priority for the spanning tree in question, and selects for itself a root bridge priority that will ensure switch 420's election as the root bridge upon a recalculation of the spanning tree. Switch 420 then instigates a recalculation of the spanning tree.
After recalculation of the spanning tree, switch 420 is elected as the root bridge for the spanning tree in question, as shown in diagram 414. Because the STP root bridge and PIM forwarder are now aligned, traffic efficiency for the multicast traffic originating from source S is restored.
In a similar embodiment, switch 430 (diagram 412) can recognize that it is no longer the PIM forwarder for the multicast traffic in question, adjust its bridge priority so that it will no longer be the root bridge for the spanning tree that forwards traffic from source S, and initiate recalculation of the spanning tree to relinquish its root bridge status.
Recognition of events such as the one shown in
Events that cause spanning tree reconvergence according to some embodiments can be events other than traffic-related events. One example is a change in the capabilities of a switch that do not directly affect the link capabilities of the switch's spanning tree ports. For two switches with similar processing power, the one that has a redundant management module, a redundant power supply, or a redundant switch fabric module would be a better choice for the root switch. Other factors such as location of the switch in the physical network topology and the logical (VLAN) topology may also affect precedence in the root selection algorithm. As an example of how hardware considerations could affect root bridge desirability, consider a switch that is chosen to be a spanning tree root switch, and then subsequently one of several ganged switch fabric modules on the switch malfunctions and is shut down. Under such a condition, all external ports of the switch may continue to function normally, but the switch may not be able to switch traffic at its normal line rate.
Current spanning tree solutions do not react to such events. According to a present embodiment, when a second switch with sufficient internal switching capacity and similar location in the topology as the impaired switch exists, the second switch can be automatically reconfigured to assume the role of the spanning tree root bridge when the capabilities of the first switch are compromised. In a minimal implementation, the bridge priority of the switch experiencing a partial internal failure can be reduced (by increasing the numerical value of the bridge priority to a second value), and then the switch forces a spanning tree reconvergence. Other, more complex reconfiguration formulae can recalculate a bridge priority to reflect the remaining redundancy and/or throughput of the switch. Also, in an AMSTP implementation where particular STIs rely on particular internal switch capabilities, a failure that affects the availability or redundancy of those particular capabilities could affect the bridge priority for some instances differently than others.
Weighed against the preference for a root bridge change in such circumstances are the undesirable consequences of a topology change. For instance, some traffic can be lost while the network reconverges. Also, at a topology change the MAC address and ARP (Address Resolution Protocol) tables in each switch are flushed, causing substantial packet flooding in the network. As these penalties may in some cases be worth forcing a topology change while not in others, a mechanism can be put in place to tailor topology change behavior depending on the observed conditions.
To implement dynamic spanning tree recalculation based on switch capability changes in one embodiment, the network administrator designates a group of switches that are capable of becoming STP root bridges. Other switches in the spanning tree but not part of the designated group that can become root bridges are prevented from ever becoming a root bridge (e.g., by assigning these switches a bridge priority high enough to insure their non-selection as a root bridge as long as at least one switch in the designated group is operating).
For switches in the designated group, an algorithm on each switch calculates a bridge priority to be used in election of a root bridge. The existing algorithm for selection of a root bridge operates such that the switch with the lowest bridge identifier (the bridge priority prepended to the bridge MAC address) becomes the root switch. This approach guarantees that one and only one switch will qualify to become the root for the spanning tree topology, since no two properly configured switches can have the same MAC address.
In this embodiment, the bridge priority portion of the bridge identifier is allowed to vary for switches in the group based on parameters known at the time of spanning tree configuration. Each resource in a switch is assigned a value in terms of a fraction of the entire range of bridge-priority. Addition of the resource to the switch could improve the priority for spanning tree instances on that switch by the assigned value, whereas removal of the resource (either manually or due to some failure) could worsen the priority. As an example, a redundant switch fabric module (SFM) could be assigned a value of 4096. Similar values can be assigned to redundant route processing modules (RPMs), power modules, etc. An even higher value, e.g., 16384, can be assigned to the presence of each high-speed uplink interface on the switch.
Each switch is assigned a base priority, to which the priorities for redundant modules, uplink interfaces, etc., are added to arrive at a bridge priority. The difference between the base priorities of an intended primary root switch and an intended secondary root switch are indicative of the network administrator's willingness to reconfigure the network upon failure of each of these resources. For example, Switch A is configured with base priority 12288. Switch B is configured with base priority 20480. All other switches in the LAN are configured with a base priority of 61440. Since bigger numerical priorities are worse, Switch A would be elected the root bridge. Assume that the lack of a redundant SFM is assigned a value of 4096 and the lack of a redundant RPM is assigned a value of 8192. If A loses a SFM due to some failure, it would increase its numerical priority up to 12288+4096=16384. Switch A, after the loss of its redundant SFM, compares its new bridge priority to that of the other switches (as they existed at the time of the last bridge identifier exchange). As 16384 still exceeds the bridge priority of the other switches' bridge priorities, Switch A need not initiate a topology change since it would remain the root switch. At this point, if A also lost the redundant RPM, it would increase its numerical priority up to 16384+8192=24576. This event would cause switch B to become the switch with the lowest numerical priority, and switch A therefore initiates a topology change event.
Even though for current spanning tree implementations the bridge priority can be increased or decreased in increments of 4096 only, it is possible to apply any value to a resource. For example, SFM failure could be assigned the value of 2048. If the base priority of a switch A is 12288, one SFM failure would not cause any change to its bridge priority. It will take two SFM failures to worsen its priority to the next higher value of 16384. The failure or recovery of switch resources (SFM, RPM, power modules, etc.) is not communicated directly to any other switch in the spanning tree topology. Any automatic update to the bridge priority value resulting from a SFM failure would appear as a manual change in bridge priority to other switches, the next time that bridge identifier is communicated to the other switches.
The above examples can also be expanded to individual instances of the spanning tree in an MSTP or AMSTP scenario. The administrator can, for example, specify on a per-instance basis whether the bridge priority for that instance should adjust as a result of addition or deletion of resources on the switch.
In a switch, adjustments to the bridge priority can be specified for a variety of events in a manner other than specified above. For instance, in a system that normally operates with 8+1 SFM redundancy, different bridge priority adjustments can be assigned for nine operational SFMs, eight, seven, etc., and these adjustments need not be linear with respect to operational SFMs. As another example, a temperature problem on one or more boards of a switch may be assigned a bridge priority adjustment, as the temperature problem may indicate an imminent hardware problem. Also, the loss of one of several uplink interfaces on the root switch can be assigned one bridge priority adjustment, with a substantially more severe bridge priority adjustment for loss of all uplink interfaces on the switch.
In MSTP and AMSTP, the configuration of each spanning tree generally relies on some assumed traffic characteristics for the traffic mapped to each spanning tree. In the embodiments above, this is also true to at least some extent—although the spanning tree topology is dynamically rearranged for a spanning tree based on certain events, the traffic bound to each spanning tree instance is left unchanged. In some cases, however, actual traffic characteristics for a given traffic flow cannot be accurately predicted in advance, or the sheer number of potential traffic flows makes it impracticable to map each flow to an MSTP or AMSTP instance. Some traffic may also be substantial but occurring for only a short time each day (for instance), and thus unsuited to a static mapping.
Thus in a traditional MSTP or AMSTP spanning tree domain, some traffic can be assigned to appropriate spanning tree instances that generally allows the traffic to follow a least cost path through the domain. Unanticipated traffic variations within an assigned traffic classification may cause some traffic in the classification to be forwarded in a suboptimal manner. With respect to unclassified traffic, that traffic will use the Layer 2 topology generated by the default spanning tree instance (instance 0, the CIST). In many cases, the unclassified traffic will encounter a suboptimal load distribution due to its use of the CIST. Generally, any static mapping will at least sometimes fail to optimally distribute traffic across the network.
In many networks, then, at least some traffic could benefit from a spanning tree that exhibits some dynamic flexibility in response to changing traffic conditions. The embodiments described below allow an identified traffic category to be assigned to either (a) an existing spanning tree instance that is more suitable for the traffic category than its current instance, or (b) a new spanning tree instance created for that traffic category. The following example shows a dynamic assignment of this type, and a mechanism for an entity to cause such a dynamic assignment.
Referring next to diagram 512 of
According, e.g., to one of the techniques previously described, a network entity recognizes the existence of the multicast group B traffic and its use of a suboptimal spanning tree. That entity (or a communicating entity, e.g., switch/router 520) informs the AMSTP spanning tree domain participants that multicast group B traffic will be assigned to a STI 13, for instance by a method that will be described below. STI 13 can be a new spanning tree instance that is to be calculated by the switches in the domain, or an existing spanning tree instance that has paths and a root bridge that are desirable for the multicast group B traffic.
Diagram 514 shows one possible result of the new, dynamic mapping for multicast group B. STI 13 has a root bridge (switch/router 520) that is the same entity as the PIM forwarder for multicast group B. With a new mapping for multicast group B traffic to STI 13, multicast group B traffic now follows an optimized path according to STI 13 to its local destination endpoint.
A few other points regarding
As mentioned, the dynamic mapping of the multicast group B traffic can be based on the observation of an event, e.g., by control packet snooping, SNMP protocol state monitoring, etc. Another alternative is the direct observation of a traffic flow that appears to be unmapped. For instance, in
According to AMSTP, a wide variety of traffic attributes can be used to map traffic to specific spanning tree instances according to a static mapping. Although in principle all such attributes are available for dynamic mapping, in an actual implementation a network administrator will generally desire to specify certain attributes that can be dynamically mapped to a spanning tree and/or certain attributes that cannot be dynamically mapped to a spanning tree. Embodiments can use access-list command syntax to tailor the dynamic spanning tree mapping behavior.
Generally, access lists have been used to select specific traffic types that will always be dropped or diverted by a switch/router to a port other than the port that a normal routing lookup would specify. Such access lists can specify the traffic of interest using a wide variety of parameters, including:
Access list commands use a syntax such as the following:
permit <IP-Protocol #> <Src-IP> <Src-Mask> <Dst-IP> <Dst-Mask>
deny <TCP> <Src-IP> <Src-Mask> <TCP-Flag> <TCP-Src-Port> <Dst-IP>
In dynamic spanning tree mapping embodiments, an access list (ACL) can be used to define whether a particular traffic flow is allowed to cause network reconfiguration and be mapped to a non-CIST or non-static spanning tree instance. The ACL deny statements identify, e.g., known traffic flows that should follow the CIST topology and should not be dynamically mapped or cause any kind of spanning tree reconfiguration. For traffic streams that do not hit any permit or deny entries, a network administrator can select how that stream is to be handled. For instance, in one handling method a traffic stream that hits no permit or deny entries in the ACL will not cause any reconfiguration and will follow the usual path through the network, which could be through the CIST. There can be, however, an optional system log message, SNMP trap, or some other form of indication made to the network administrators to allow them to identify traffic flows for which explicit permit or deny statements can be added to the ACL. In another handling method, traffic that does not hit any entry (permit or deny) in the ACL can be analyzed for possible optimization if it meets all other criteria necessary to cause reconfiguration.
The following specific example shows one possibility for using an ACL. In a hypothetical network, the following ACL can be applied to Layer 3 traffic that is not mapped to a non-CIST instance:
1) deny 172.16.1.10 255.255.255.255 184.108.40.206 255.255.255.255
2) deny 10.1.1.10 255.255.255.255 188.8.131.52 255.255.255.255
3) permit any 18.104.22.168 255.255.255.255
4) deny any
In this example, 172.16.1.10 and 10.1.1.10 are local hosts that are also multicast sources for the multicast group 220.127.116.11. This multicast group also has sources outside the local network. The first two entries do not allow any multicast traffic from the two local sources to cause any network reconfiguration. The third entry, however, allows other multicast traffic to this group destination address from any other source (internal or external to the local network) to potentially cause reconfiguration of the Layer 2 topology in order to achieve an end-to-end optimized path. The last entry (4) prevents any other traffic flow from causing any reconfiguration of the local network topology. Entry 4 prevents unknown traffic flows from causing reconfiguration of Layer 2 topologies in the local network. Other ACL filters, included above entry 4, can allow and disallow other specific flows to affect the Layer 2 topology.
In an embodiment that used control packet snooping or protocol monitoring, a separate access list can be used to identify the control protocol that should be snooped or monitored and acted upon in an attempt to optimize a traffic path. When such an ACL permits a protocol, e.g., PIM, then the dynamic STP would snoop PIM control traffic in order to determine the PIM Forwarder location for a multicast group. When the PIM forwarder for a multicast group G, for instance, is not on the same switch that is the AMSTP root for group G (or no AMSTP root for group G exists), and the traffic for group G equals or exceeds the pre-configured thresholds, then reconfiguration of the Layer 2 topology can be triggered to optimize the end-to-end traffic path for group G. A protocol that is denied in the protocol-ACL will not be snooped (or monitored), and no attempt will be made to correct the un-optimized end-to-end path resulting from disconnect between the Layer 2 topology and the topology for the protocol that is denied. For instance, in the following exemplary list HSRP protocol packets will not be snooped, VRRP and PIM packets will be snooped, and all other protocol packets will not be snooped.
1) deny HSRP
2) permit VRRP
3) permit PIM
4) deny any any
Any change in the topology of the two monitored protocols causes an evaluation of the end-to-end traffic path for the traffic affected by the topology change. If any suboptimal paths are discovered, a reconfiguration might follow.
Another potential feature for the dynamic spanning tree approach is a control function that lessens spanning tree reconfiguration frequency should too-frequent reconfiguration become an issue. In one approach, the spanning tree members can log the triggers that cause them to request spanning tree reconfiguration. If a recurring trigger event is repeatedly causing reconfiguration as it appears and then disappears, the thresholds for that trigger event can be adjusted automatically, or an alert can be generated to a network administrator, who can then use an access control list entry to adjust the response to that trigger event, or deny that event from causing reconfiguration.
The actual spanning tree recalculation can also be limited in frequency. The spanning tree members can accumulate requests for reconfiguration, e.g., for several minutes, between possible spanning tree reconfiguration points. All pending reconfiguration requests can then be processed at once upon a signal, e.g., from the CIST root bridge. Any requests that are withdrawn in the interim, e.g., due to sporadic traffic, will never cause reconfiguration of the spanning tree.
In traditional spanning tree approaches, a network administrator manually provisions bridge and port priorities on each switch in a spanning tree domain, and identical MSTP VLAN-to-instance mapping tables on each switch. To change the MSTP mapping, new mapping tables must be loaded to each switch, digest values must be recalculated, and the spanning tree must be restarted. Thus a new approach for provisioning dynamic instance mapping information is needed for the rapid reconfiguration dynamic algorithm discussed above. One such approach has been devised, and is described below as a Generic Instance Registration Protocol (GIRP). Note that GIRP is primarily intended for regions that run MSTP, AMSTP, or a similar multiple-spanning-tree-instance protocol.
GIRP is built in this embodiment on the framework already in place for GARP, the Generic Attribute Registration Protocol. GARP is described in detail in Section 12 of IEEE 802.1D, which is incorporated herein by reference. GARP PDUs (Protocol Data Units) are exchanged in a reachability tree formed in a subset of a spanning tree topology. GARP allows a participant in a given GARP Application to make or withdraw declarations of attributes, and for those declarations (or withdrawals) to result in the registration (or removal of registrations) of those attributes with the other GARP Participants for that Application. Each GARP Application uses a unique group MAC address as the destination address of GARP PDUs; thus the GIRP implementation assumes a designated group MAC address be made available for the GIRP Application.
A GIRP PDU takes the following format, with a two byte protocol ID followed by a variable number of messages. The protocol ID identifies the GARP protocol.
2 bytes
Protocol ID
. . .
Each GIRP message contains a one byte attribute type descriptor, followed by a variable number of attributes of that attribute type, and an end mark. The attribute types defined for GIRP are specific to GIRP, and will be explained further below. The end mark is coded as 0.
GIRP Message
1 byte
Attribute type
Attribute 1
. . .
Attribute n
End mark
Each GIRP attribute contains a one byte attribute length field descriptor, followed by a one byte attribute event and an attribute value of the specified attribute length. The allowable attribute events are those defined by the GARP specification:
GIRP Attribute
1 byte
1 byte
1 byte
Attribute length
Attribute event
Attribute value
The allowable attribute events are those defined by the GARP specification:
The attribute value is encoded in accordance with a definition specific to the attribute type.
In the GIRP application, the formed reachability tree is a subset of the CIST (MSTP or AMSTP instance 0) topology. There is a single GIRP participant per port and all GIRP participants operate in a single GIRP context corresponding to the CIST. In switches that support GIRP, the received PDUs are submitted to the GIRP Participant associated with the receiving port for further processing. In switches that do not support GIRP, all such PDUs are submitted to the Forwarding process.
GIRP PDUs are carried over the CIST topology, and distribute information about the mapping between an attribute such as VLAN-ID, Ethertype, etc., and a spanning tree instance ID. Using GIRP, the switches in the spanning tree domain can register and de-register GARP-formatted attributes such as the MSTP region name, revision number, and instance-to-attribute mapping. GIRP propagates the attribute information to other devices in the spanning tree. The operation of GIRP defines the following attribute types:
Attribute Type
Attribute value
1 - MSTP Region Name
Character string up to 32 characters in length
2 - MSTP Revision Number
Integer between 0-65535
3 - MSTP Instance ID
Integer between 0-4095 (values between 1-63
supported for now)
Integer between 1-4094
5 - Multicast Group Address
IPv4 (4 bytes) or IPv6 address (16 bytes)
6 - EtherType
Integer - 2 bytes (0x0600-0xffff)
128 - VLAN-ID-range-Min
Integer between 1-4094
129 - VLAN-ID-range-Max
Integer between 1-4094
130 - Multicast Group Address range Min
IPv4 (4 bytes) or IPv6 address (16 bytes)
131 - Multicast Group Address range Max
IPv4 (4 bytes) or IPv6 address (16 bytes)
132 - EtherType range Min
Integer - 2 bytes (0x0600-0xffff)
133 - EtherType range Max
Integer - 2 bytes (0x0600-0xffff)
Other attribute types, e.g., for other traffic attributes or Layer 2/Layer 3 protocols, can be added as well to extend the operation of GIRP. Of the types defined above, the following explanations apply. The MSTP Region Name (the protocol run in the region could be AMSTP as well as MSTP) is the name assigned to the region by the network administrator, and is the same name propagated in the MSTP BPDUs. Likewise, the MSTP Revision Number is the current revision number propagated in the MSTP BPDUs. An MSTP Instance ID refers to one of the allowable spanning tree instance IDs for the region.
The VLAN-ID indicates one of the VLAN-IDs defined for the region. A Multicast Group Address is an IP address (version 4 of version 6) assigned to a given multicast group. An EtherType is one of the values allowed in the EtherType field of a Layer 2 Ethernet packet header.
The remaining attributes in the table are range attributes for VLAN-ID, Multicast Group Address, and EtherType. Without a range attribute, if VLAN-IDs 1-10 were mapped to MSTP STI 1, the GIRP message for communicating the mapping would contain the following GIRP attributes in this order: <Instance ID=1> <Vlan 1> <Vlan 2> . . . <Vlan 10> <End>. Rather than including all VLANs in the GIRP message, a range attribute pair can be used to specify that all values of the attribute, including the minimum and maximum values specified, will be mapped to the instance ID carried in the preceding instance attribute. Using range attributes, the GIRP message for the preceding example would contain the following GIRP attributes: <Instance ID=1> <Vlan-Range 1> <Vlan-Range 10> <End>.
When further attributes are added to the attribute definitions above, the suggested attribute type coding reserves values 0-127 for standard GIRP attributes and values 128-255 for extended GIRP attributes.
The ordering of attributes in a GIRP message should abide by the following rules:
Whether a switch is allowed to register attributes or not, all switches in the domain are expected to have MSTP/AMSTP enabled. Hence all switches can receive GIRP messages over the CIST topology in order to participate in dynamic traffic mapping. The mapping of instances to attributes is, however, limited to one MSTP region. Multiple MSTP Regions communicate with each other solely based on the CIST information. Hence the GIRP PDUs should be limited to one region only, and should not be propagated on external links.
GIRP allows both end-stations and bridges in a bridged LAN to issue and revoke declarations relating to the instance-to-attribute mapping. The effect of issuing such a declaration is that each GIRP participant that receives the declaration will create or update the instance mapping in the spanning tree configuration. This can result in reconfiguration of the spanning tree topology and possibly modification or addition or removal of entries in the Filtering database.
The act of registering/deregistering an instance-to-attribute mapping affects the Spanning Tree configuration on each affected switch, and may result in a topology change. Thus it may be desirable in a given implementation to restrict the attribute types that a given switch can register, on a per-attribute-type basis. For example, in a particular network topology, only the core switch(es) could be allowed to register MSTP Region and MSTP Revision number attributes, whereas any switch could register a new instance-to-attribute mapping. This access should be configurable by the network administrator on a per-attribute basis.
Several additional restrictions should also be observed with the GIRP protocol, as follows:
The following services are available using GIRP:
MSTP Region Name Registration
The MSTP Region name registration service allows switches participating in the Spanning Tree topology to:
Register the name of the MSTP region.
De-register the name of the MSTP region.
MSTP Revision Number Registration
The MSTP Revision number registration service allows switches participating in the Spanning Tree topology to:
Register the revision number for the MSTP region.
De-register the revision number for the MSTP region.
MSTP Instance-to-Attribute Mapping Definition
The MSTP Instance-to-Attribute mapping registration service allows switches participating in the Spanning Tree topology to:
Register an MSTP Instance ID and map one or more attributes to this Instance ID.
De-register an MSTP Instance ID or one or more attributes mapped to the Instance ID.
The use of these services will result in propagation of the MSTP information across the CIST Spanning Tree topology, causing a reconfiguration of the spanning tree in all the switches. This can affect the frame forwarding behavior of those switches and end stations.
A few short examples will now be presented to further clarify the use of GIRP to dynamically adjust a spanning tree configuration.
Once the switches know the identities of the static STIs for which each is a root bridge, the switches can proceed to dynamically map traffic to each instance. For instance, switch 610 can observe that it is the network entry point for substantial traffic flows for two multicast group addresses, an address M1 and an address M2. Switch 610 proceeds to register and declare its three STIs and mappings to addresses M1 and M2, by sending the following GIRP messages on the CIST:
JoinIn(MSTP Region Name RegionExample)
JoinIn(MSTP Revision Number 1)
JoinIn(MSTP Instance ID 0)
JoinIn(MSTP Instance ID 1) JoinIn(Multicast Group Address M1)
JoinIn(MSTP Instance ID 4) JoinIn(Multicast Group Address M2)
The first two JoinIn messages indicate that switch 610 is a GIRP entity for AMSTP Region RegionExample. Switch 610 also issues a JoinIn message for MSTP Instance ID 0, thereby preventing any other entity from registering traffic attributes to the default spanning tree instance (all unregistered traffic already passes through the default spanning tree instance). Switch 610 issues a JoinIn message pair for MSTP Instance ID 1 and Multicast Group Address M1. Each GIRP-enabled switch in the spanning tree that receives this message updates its filtering database to note the association between MSTP Instance ID 1 and Multicast Group Address M1. Similarly, Switch 610 issues a JoinIn message pair for MSTP Instance ID 2 and Multicast Group Address M2 to map that association across the spanning tree region.
Switch 620 can observe that it is the network entry point for substantial traffic flows for two multicast group addresses M3 and M4. Switch 620 proceeds to register and declare the two STIs for which is it the root bridge and mappings to addresses M3 and M4, by sending the following GIRP messages on the CIST:
LeaveAll JoinIn(MSTP Region Name RegionExample) JoinIn(MSTP Revision Number 1) JoinIn(MSTP Instance ID 2) JoinIn(Multicast Group Address M3) JoinIn(Multicast Group Address M4) JoinIn(MSTP Instance ID 5)
This message group operates in similar fashion to the message group issued by switch 610. Switch 620, however, chose to assign the two multicast group addresses M3 and M4 to the same MSTP Instance. Switch 620 has registered and declared MSTP Instance ID 5, although it is not presently mapping traffic to that instance. Depending on implementation, it may or may not be preferable to allow switches to register an instance to "reserve" it, even though it presently is not mapping any attribute to that instance. When preferable, each switch could be guaranteed a set minimum number of instances for its use, and it could reserve the minimum number in this fashion.
Assume that switch 630 has five VLANs with VLAN-IDs 6-10 that it desires to map to one of the spanning tree instances for which it is root. Switch 630 proceeds to register and declare instances and attributes as follows, by sending the following GIRP messages on the CIST:
LeaveAll JoinIn(MSTP Region Name RegionExample) JoinIn(MSTP Revision Number 1) JoinIn(MSTP Instance ID 6) JoinIn(VLAN-ID-range-Min 6) JoinIn(VLAN-ID-range-Max 10)
Switch 630 has now mapped traffic for VLAN-IDs 6 to 10 to instance 6. These VLAN-IDs could be identified from unmapped traffic flows in an embodiment. In the alternative, these VLAN-IDs can also be statically provisioned on switch 630—in a manner that ties the VLAN-IDs to the switch as a root bridge and not to a specific VLAN, as a standard MSTP mapping would do. For instance, a GIRP boot table can specify attributes that a switch should acquire to itself as a root bridge upon boot-up. After the static spanning tree instances are resolved, switch 630 selects one or more spanning tree instances for which it has become the root bridge, and uses GIRP to map the attributes in the GIRP boot table to those spanning tree instances. With this approach, a network administrator only has to provision a mapping on one switch, and does not have to explicitly map the attributes to a specific spanning tree instance.
Also, as part of this example, switch 630 has not registered spanning tree instance 3, for which it is the root bridge. As the spanning tree participants know that spanning tree instance 3 exists but is unused, another entity in the network (switch, endpoint, or management node) that has analyzed a traffic attribute and found that the attribute would be best handled through switch 630, that entity can issue a GIRP command to bind the attribute to STI 3. Although not shown in the example, each switch could maintain root bridge status for at least one STI that it does not register, allowing other network entities to direct traffic through that switch.
Another possibility in an embodiment is the dynamic addition of an instance to the spanning tree topology. For instance, suppose that switch 630 determines that it is receiving unmapped multicast group traffic for a multicast group address M5, and the traffic is following an unoptimized path on the CIST through switch 610. At this point, switch 630 has mapped five VLANs to STI 6, and another entity has registered STI 3. Thus switch 630 can choose to create a new spanning tree instance, rather than adding multicast group address M5 to STI 6 (although this is possible).
To create the new spanning tree and map traffic for multicast group address M5 to the new spanning tree, switch 630 selects an unused instance ID in the range 7-63, e.g., instance ID 9. Switch 630 issues the following GIRP messages:
JoinIn(MSTP Instance ID 9) JoinIn(Multicast Group Address M5)
The GIRP Participants do not immediately add a mapping between MSTP Instance ID 9 and Multicast Group Address M5 to their Filtering databases, since no spanning tree instance ID 9 exists. The spanning tree participants exchange new MSTP BPDUs that contain configuration messages for the new instance 9. Switch 630, as the switch that registered the instance ID, selects an advertised bridge priority for instance 9 of a lower numerical value than that selected by each other switch. The BPDUs propagate through the network and the spanning tree calculates the new spanning tree (with switch 630 as the root). Once the spanning tree has converged, each switch adds the mapping between STI 9 and multicast group address M5 to its filtering database.
Should another unmapped multicast group address M6 be identified by switch 630, it can choose to add the new address to STI 9 using the following GIRP messages:
JoinIn(MSTP Instance ID 9) JoinIn(Multicast Group Address M6)
This time, spanning tree instance 9 exists, and thus the GIRP Participants simply add the new mapping between MSTP Instance ID 9 and Multicast Group Address M6 to their Filtering databases.
At a later time, switch 630 may detect that it is no longer receiving traffic for the multicast group M5. After no traffic has been received for a significant time, switch 630 can decide to unmap the attribute from STI 9. Switch 630 issues the following GIRP messages:
JoinIn(MSTP Instance ID 9) LeaveIn(Multicast Group Address M5)
Each GIRP participant responds by removing the mapping between STI 9 and multicast group address M5 from its Filtering database. Should further traffic be received for multicast group address M5, that traffic will be switched using the CIST.
At a later time, should traffic for address M6 also drop below the applicable thresholds, switch 630 may choose to deregister that attribute, and may also choose to deregister spanning tree instance 9 and return that instance ID to the free pool. Switch 630 issues the following GIRP messages to cause all switches to remove address M6 from their filtering databases and remove STI 9 from their BPDUs:
LeaveIn(MSTP Instance ID 9) LeaveIn(Multicast Group Address M6)
The LeaveIn message for Multicast Group Address M6 could be omitted in this case, as the removal of MSTP Instance ID 9 would cause removal of all attributes linked to that instance.
Because switches are allowed to randomly select an unused STI when a new STI is needed, it is possible that two switches could select the same unused STI concurrently. This would result in a collision, as the other GIRP Participants would receive two JoinIn messages for the same unused MSTP Instance ID. Whenever a switch detects a collision for an MSTP Instance ID that is has just included in a GIRP JoinIn message (by receiving a JoinIn message from another switch for the same MSTP Instance ID), that switch issues a LeaveIn Message for that instance, waits a random amount of time (from 0 to X seconds), and then randomly selects an unused instance ID and attempts to register again. The value of X could have a default value such as 30 seconds, but could also be configurable by the network administrator.
Digests such as those used in MSTP and AMSTP can be defined across the dynamic attributes, with recalculation as attributes are dynamically added and removed from the spanning tree. This functions as a check that all switches are operating with the same dynamic attribute mapping. For instance, each GIRP Participant can save GIRP state in a predefined order, for which a digest is recalculated whenever the GIRP state changes. If for some reason a GIRP Participant loses a registration or removal, its digest may disagree with those sent by other switches. In such a case it can issue a GIRP JoinEmpty message for the MSTP Region Name, causing all switches to resend JoinIn messages for all of their instances and attributes.
GIRP PDUs are not exchanged across dynamic STP (DSTP) Regions.
Those skilled in the art will appreciate that the embodiments and/or various features of the embodiments can be combined in other ways than those described to implement dynamic spanning tree concepts covered by the present disclosure. Although specific enabling approaches have been described, others exist. For instance, instead of a GARP-based vehicle for conveying dynamic instance and attribute mapping, the MSTP BPDUs could be modified to carry additional information necessary to implement dynamic spanning tree configuration.
A variety of hardware, software, and combination approaches are possible for implementation of an embodiment and various features thereof. No limitation to a specific approach is suggested or intended by this disclosure.
Although the specification may refer to "an", "one", "another", or "some" embodiment(s) in several locations, this does not necessarily mean that each such reference is to the same embodiment(s), or that the feature only applies to a single embodiment.
|Cited Patent
|Filing date
|Publication date
|Mar 7, 1990
|Sep 22, 1992
|Digital Equipment Corporation
|Utilization of redundant links in bridged networks
|Apr 23, 1992
|May 24, 1994
|Xyplex Inc.
|Parallel bridging
|Nov 9, 1998
|Dec 11, 2001
|3Com Corporation
|Spanning tree with rapid forwarding database updates
|May 8, 2001
|Aug 20, 2002
|International Business Machines Corporation
|Alternate use of data packet fields to convey information
|Mar 1, 1999
|Feb 4, 2003
|Cisco Technology, Inc.
|Virtual local area network membership registration protocol for multiple spanning tree network environments
|Feb 1, 2000
|Sep 2, 2003
|Hewlett-Packard Development Company, L.P.
|Bridged network topology acquisition
|Nov 30, 1999
|Jan 13, 2004
|Cisc Technology, Inc.
|Fast convergence with topology switching
|Aug 30, 2001
|Feb 24, 2004
|Motorola, Inc.
|System and methods for distributed connection and mobility processing in a multicast IP network incorporating multi-cell location areas
|May 31, 2001
|Aug 3, 2004
|Motorola, Inc.
|Method for improving packet delivery in an unreliable environment
|Dec 22, 2000
|Nov 2, 2004
|Cisco Technology, Inc.
|Shared spanning tree protocol
|Mar 1, 2001
|Nov 30, 2004
|Onfiber Communications, Inc.
|Broadband tree-configured ring for metropolitan area networks
|Jan 7, 2002
|Jul 12, 2005
|Corrigent Systems Ltd.
|Fast failure protection using redundant network edge ports
|Oct 17, 2000
|Aug 30, 2005
|Cisco Technology, Inc.
|Multiple instance spanning tree protocol
|Jun 30, 2000
|Oct 11, 2005
|Intel Corporation
|Method and apparatus for avoiding transient loops during network topology adoption
|May 31, 2001
|Aug 8, 2006
|Kabushiki Kaisha Toshiba
|Computer system and method for aiding log base debugging
|Apr 29, 2002
|Dec 19, 2006
|Canon Kabushiki Kaisha
|Method for the broadcasting of a data packet within a switched network based on an optimized calculation of the spanning tree
|Dec 20, 2002
|May 27, 2008
|Foundry Networks, Inc.
|Optimizations and enhancements to the IEEE RSTP 802.1w implementation
|Jun 9, 2003
|Dec 1, 2009
|Foundry Networks, Inc.
|System and method for multiple spanning tree protocol domains in a virtual local area network
|Jan 27, 2001
|Oct 25, 2001
|Banwell Thomas Clyde
|Physical layer auto-discovery for management of network elements
|Jan 4, 2001
|Aug 29, 2002
|Oberman Stuart F.
|Dynamic selection of lowest latency path in a network switch
|Jul 20, 2001
|Mar 20, 2003
|Ashutosh Mate
|Selective routing of data flows using a TCAM
|Sep 4, 2003
|Apr 1, 2004
|Goldman Tomasz J.
|Spanning tree recovery in machine networks
|May 29, 2003
|Dec 2, 2004
|Hewlett-Packard Co.
|Method and apparatus for tracking a plurality of image devices in a network
|Sep 19, 2003
|Mar 24, 2005
|Zhichen Xu
|Providing a notification including location information for nodes in an overlay network
|Dec 28, 2004
|Jan 12, 2006
|Fujitsu Limited
|Method for preventing control packet loop and bridge apparatus using the method
|Nov 17, 2005
|May 25, 2006
|Nortel Networks Limited
|Method and apparatus for implementing multiple portals into an Rbridge network
|Jun 14, 2005
|Dec 14, 2006
|Premkumar Jonnala
|Method and apparatus for preventing DOS attacks on trunk interfaces
|Dec 15, 2005
|Jun 21, 2007
|Jeremy Touve
|System and method for implementing multiple spanning tree protocol automatic 802.1Q trunking
|Javvin Network Management & Security, GARP: Generic Attribute Registration Protocol, Aug. 1, 2005, pp. 1-3, IEEE 802.1P, http://www.javvin.com/protocolGARP.html, Javvin Technologies, Inc., California, USA.
|Javvin Network Management & Security, GMRP: GARP Multicast Registration Protocol, Aug. 1, 2005, pp. 1-3, IEEE 802.1P, Javvin Technologies, Inc., California, USA.
|Javvin Network Management & Security, GVRP: GARP VLAN Registration Protocol, Aug. 1, 2005, pp. 1-3, IEEE 802.1P and IEEE 802.1Q, Javvin Technologies, Inc., California, USA.
|Javvin Network Management & Security, IEEE 802.1p: LAN Layer 2 QoS/CoS Protocol for Traffic Prioritization, Aug. 1, 2005, pp. 1-3, IEEE 802.1Q (VLANs tagging), Javvin Technologies, Inc., California, USA.
|Office Action of Nov. 20, 2008, from parent U.S. Appl. No. 11/455,948.
|Response to Office Action of Nov. 20, 2008, filed Apr. 20, 2009, from parent U.S. Appl. No. 11/455,948.
|Tobagi, Fouad A., Molinero-Fernández, Pablo, and Karam, Mansour J., Study of IEEE 802.1p GARP/GMRP Timer Values, The GARP/GMRP Protocol, pp. 1-28, IEEE 802.1p standard, Stanford University, Jun. 30, 2006.
|Citing Patent
|Filing date
|Publication date
|Mar 22, 2011
|Juniper Networks, Inc.
|Configuring networks including spanning trees
|Sep 24, 2007
|Apr 12, 2011
|Siemens Aktiengesellschaft
|Method for reconfiguring a communication network
|Jan 31, 2007
|May 10, 2011
|Hewlett-Packard Development Company, L.P.
|Method of distributing multiple spanning tree protocol configuration
|Mar 5, 2009
|May 17, 2011
|Alcatel-Lucent Usa Inc.
|Network design method
|Oct 9, 2007
|Sep 6, 2011
|Telefonaktiebolaget Lm Ericsson (Publ)
|Method for discovering the physical topology of a telecommunications network
|Jan 29, 2009
|Jul 3, 2012
|Kabushiki Kaisha Toshiba
|System for remote supervision and diagnosis using mobile program
|Oct 7, 2009
|Sep 18, 2012
|Rockstart Bidco, LP
|Method and apparatus for exchanging routing information and establishing connectivity across multiple network areas
|Feb 4, 2008
|Feb 5, 2013
|Alcatel Lucent
|Method and apparatus for sending and receiving multicast packets on a multicast tree
|Sep 29, 2010
|Jul 9, 2013
|International Business Machines Corporation
|Virtual switch interconnect for hybrid enterprise servers
|Feb 11, 2011
|Feb 18, 2014
|Juniper Networks, Inc.
|Configuring networks including spanning trees
|Nov 5, 2012
|Jul 22, 2014
|International Business Machines Corporation
|Virtual switch interconnect for hybrid enterprise servers
|Sep 30, 2011
|Sep 16, 2014
|Hewlett-Packard Development Company, L.P.
|Method of reducing power consumption in a network
|Jan 9, 2007
|Oct 7, 2014
|Sandvine Incorporated Ulc
|Automatically maximizing network link utilization using virtual networks
|Apr 17, 2009
|Oct 7, 2014
|Canon Kabushiki Kaisha
|Video delivery apparatus and method
|Nov 15, 2008
|Oct 21, 2014
|Telefonaktiebolaget L M Ericsson (Publ)
|Multiple tree registration protocol
|Feb 13, 2013
|Jan 6, 2015
|Vmware, Inc.
|Multipath load balancing optimizations for alua storage systems
|Jun 8, 2012
|Jul 7, 2015
|Cisco Technology, Inc.
|System and method for layer-2 multicast multipathing
|Sep 7, 2012
|Jul 14, 2015
|Dell Products L.P.
|Systems and methods providing reverse path forwarding compliance for a multihoming virtual routing bridge
|Jun 25, 2012
|Oct 13, 2015
|Qualcomm Incorporated
|Spanning tree protocol for hybrid networks
|Jan 28, 2014
|Nov 3, 2015
|Juniper Networks, Inc.
|Configuring networks including spanning trees
|Jul 17, 2012
|Nov 3, 2015
|Cisco Technology, Inc.
|System and method for layer-2 network routing
|Aug 19, 2010
|Nov 24, 2015
|Nec Corporation
|Network designing system, network designing method, data transfer path determination method and network designing program
|Feb 7, 2014
|Feb 16, 2016
|Huawei Technologies Co., Ltd.
|Method, system, and switch for making bridge in MSTP join region
|Jul 23, 2012
|Mar 15, 2016
|Huawei Technologies Co., Ltd.
|Method and system for auto-configuration, and network node
|Jun 29, 2012
|Apr 5, 2016
|Sonos, Inc.
|Dynamic spanning tree root selection
|Jan 9, 2007
|Jul 10, 2008
|Michael Frank Marchetti
|Automatically maximizing network link utilization using virtual networks
|Jan 31, 2007
|Jul 31, 2008
|Hewlett-Packard Development Company, L.P.
|Method of distributing multiple spanning tree protocol configuration
|Apr 18, 2008
|Jan 22, 2009
|Paola Iovanna
|Method and apparatus for quality of service (QoS) planning for an ethernet based network
|Jan 29, 2009
|Aug 6, 2009
|Yoshikazu Ooba
|System for remote supervision and diagnosis using mobile program
|Apr 17, 2009
|Nov 5, 2009
|Canon Kabushiki Kaisha
|Video delivery apparatus and method
|Oct 9, 2007
|Jan 28, 2010
|Farkas Janos
|Method for Discovering the Physical Topology Of A Telecommunications Network
|Oct 7, 2009
|Jan 28, 2010
|Nortel Networks Limited
|Method and apparatus for exchanging routing information and establishing connectivity across multiple network areas
|Sep 24, 2007
|May 6, 2010
|Vivek Kulkarni
|Method for reconfiguring a communication network
|Sep 9, 2010
|Alcatel-Lucent Usa Inc.
|Network design method
|Feb 4, 2008
|Mar 17, 2011
|Wen Haibo
|Method and apparatus for sending and receiving multicast packets
|Nov 15, 2008
|May 19, 2011
|Farkas Janos
|Multiple Tree Registration Protocol
|Jun 9, 2011
|Juniper Networks, Inc.
|Configuring networks including spanning trees
|Dec 17, 2009
|Jun 21, 2012
|Zte Corporation
|Method and System for Rebuilding Single Ring Network Topology
|Aug 19, 2010
|Jun 21, 2012
|Yasuhiro Miyao
|Network designing system, network designing method, data transfer path determination method and network designing program
|Jun 24, 2011
|Dec 27, 2012
|Cisco Technology, Inc.
|Level of hierarchy in mst for traffic localization and load balancing
|Apr 4, 2013
|Nathan Stanley Jenne
|Method of reducing power consumption in a network
|Jul 23, 2012
|May 23, 2013
|Huawei Technologies Co., Ltd.
|Method and system for auto-configuartion, and network node
|Jun 25, 2012
|Dec 26, 2013
|Qualcomm Atheros, Inc.
|Spanning tree protocol for hybrid networks
|Jun 29, 2012
|Jan 2, 2014
|Hrishikesh Gossain
|Dynamic spanning tree root selection
|Aug 31, 2012
|Mar 6, 2014
|Cisco Technology, Inc.
|Mst extensions for flexible and scalable vn-segment loop prevention
|Sep 7, 2012
|Mar 13, 2014
|Dell Products L.P.
|Systems and methods providing reverse path forwarding compliance for a multihoming virtual routing bridge
|Feb 13, 2013
|Aug 14, 2014
|Vmware, Inc.
|Multipath load balancing optimizations for alua storage systems
|Jun 29, 2012
|Oct 10, 2012
|Method and system for port blocking
|Jun 29, 2012
|Jan 21, 2015
|Method and system for port blocking
|Oct 26, 2012
|Feb 6, 2013
|MSTP-based (Multiple Spanning Tree Protocol) network topology convergence method, equipment and system
|Oct 26, 2012
|Apr 29, 2015
|MSTP-based (Multiple Spanning Tree Protocol) network topology convergence method, equipment and system
|Apr 1, 2012
|Jan 15, 2014
|Huawei Technologies Co., Ltd.
|Method, system, and switch for adding bridge in mstp to domain
|Apr 1, 2012
|Apr 2, 2014
|Huawei Tech Co Ltd
|Method, system, and switch for adding bridge in mstp to domain
|Jun 25, 2012
|Jan 3, 2014
|Hewlett-Packard Development Company, L.P.
|Translated session information to provision a network path
|Oct 28, 2013
|May 1, 2014
|Huawei Technologies Co., Ltd.
|Multiple spanning tree protocol network topology convergence method, device and system
|Dec 10, 2014
|Jun 18, 2015
|Universidad De Alcalá
|Method for establishing and clearing paths and forwarding frames for transport connections, and network bridge
|U.S. Classification
|370/256, 370/401, 370/392
|International Classification
|Cooperative Classification
|European Classification
|Aug 25, 2006
Owner name: FORCE10 NETWORKS, INC., CALIFORNIA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:ZINJUVADIA, VISHAL;REEL/FRAME:018170/0982
Effective date: 20060619
|Jan 2, 2014
Owner name: BANK OF AMERICA, N.A., AS ADMINISTRATIVE AGENT, TE
Free format text: PATENT SECURITY AGREEMENT (ABL);ASSIGNORS:DELL INC.;APPASSURE SOFTWARE, INC.;ASAP SOFTWARE EXPRESS,INC.;AND OTHERS;REEL/FRAME:031898/0001
Effective date: 20131029
Owner name: BANK OF NEW YORK MELLON TRUST COMPANY, N.A., AS FI
Free format text: PATENT SECURITY AGREEMENT (NOTES);ASSIGNORS:APPASSURE SOFTWARE, INC.;ASAP SOFTWARE EXPRESS, INC.;BOOMI, INC.;AND OTHERS;REEL/FRAME:031897/0348
Effective date: 20131029
Owner name: BANK OF AMERICA, N.A., AS COLLATERAL AGENT, NORTH
Free format text: PATENT SECURITY AGREEMENT (TERM LOAN);ASSIGNORS:DELL INC.;APPASSURE SOFTWARE, INC.;ASAP SOFTWARE EXPRESS, INC.;AND OTHERS;REEL/FRAME:031899/0261
Effective date: 20131029
|Jan 20, 2014
|Fee payment
Year of fee payment: 4


text:
Top Online Gambling Rules to Live by
Just like every other aspect in life, there are online gambling principles that you just ought to follow so as so that you can prevail. Sure, taking part in on line casino games or having a bet on your favourite
Learn to Play Casino Craps – The Hardway Bets
Be keen, play savvy, figure out how to play casino craps the correct way! A Hardway wager is a standing wager that you can make, evacuate, increment, or reduction whenever. You wager that a hardway number will appear as a
Blackjack Betting Strategy – Maximize Your Profits Now!
Utilizing the best possible blackjack betting system will in a flash put you not far off to amplifying your benefits! Alongside the correct blackjack procedure you need the attributes of a triumphant player. The following are the qualities YOU MUST
Phonics Bingo
Phonics is a mainstream strategy for instructing kids to peruse that is based around the kid figuring out how to associate sounds with letters or gatherings of letters. For instance, the youngster would discover that the hard "k" sound is
How You Can Win at Betfair Exchange Game Baccarat
It might be the casino diversion supported most by James Bond however given the fame of baccarat on the Betting exchange, no doubt Bond is by all account not the only individual shaken yet not mixed by the amusement. The
Ohio Slots – What's Next?
Playing the slots (video lottery terminals) will soon be a reality in Ohio as state authorities at long last went to an understanding about this issue. With 2,500 machines anticipating being introduced at all the seven steed tracks before the
EuroMillions' Lottery System
EuroMillions was presented on February 2004 and from that point forward, it has given heaps of individuals the chance to win immense measure of cash from each amusement or draw. The chance to acquire colossal measure of cash from each
Sport Betting Systems – The Smart Approach to Sports Betting
Spend every time watching for recreation making a bet techniques and you will see some outlandish claims about sky rocketing your bankroll speedy. Do these recreation making a bet programs fairly work ultimately or are they only as dicy and
A Review of Poker-Edge 5 Poker Statistical Software
Review of Poker-Edge Software Online poker players have a wide decision of poker assessment programming that, when utilized effectively, helps players plug spills in their amusement. Regardless of what level of player you are, intuitive poker measurements programming devices furnish
Online Gambling Risks – Kicking Out The Ifs And Buts?
Scams There are a lot of risks worried in on-line playing. The game itself involves a lot of dangers, nonetheless, aside from this, there are lots of different risks and aren't very distinctive either. The web has unfold its wings

subset: commoncrawl


text:
Turning Point Camp, a camp held for children with emotional and mental disorders, had a successful inaugural event in Chattanooga last week and future camps are already being planned.
Attachment is at the root of most mental illnesses, according to Hardwired to Connect: The New Scientific Case for Authoritative Communities. The report (http://www.americanvalues.org/ExSumm-print.pdf) was written by a group of 33 leading children's doctors, neuroscientists, research scholars and mental health professionals. Of these mental disorders, Reactive Attachment Disorder (RAD) is often misunderstood or undiagnosed. Most local therapists know little about it. While all professional therapists have heard of disorders such as Oppositional Defiance Disorder, OCD, ADHD and Anxiety disorders, few are familiar or experienced in the treatment of RAD. Due to current research and more accurate diagnoses, however, this is changing.
Turning Point Camp Host Jennie Landreth's own adopted daughter was diagnosed with RAD. For years, Ms. Landreth was the target of her daughter's rage and anxiety that was, some say, caused by trauma she experienced before her adoption.
"We had gotten to the end of our rope and were terrified of what lay ahead for our daughter. We had tried everything," said Ms. Landreth. "We sought help from every professional we could find and still just ended up watching our daughter get worse and worse. After how much the camp we attended helped my family - it was just the next logical step," Landreth says. "We have to keep passing along this message because local professionals don't know enough about Reactive Attachment Disorder to be able to help the families in our community. This is a great way to train them as well and we hope to have more local therapists become involved in this camp. It is my hope that if I can help even just one family with the camp and the seminars, that I can pay it forward and keep hope alive for other families that are out there struggling with RAD and other mental disorders."
According to attendees, the camp was successful in helping not just one family, but many that were feeling hopeless and desperate due to the aforementioned disorders that existed within their own families.
Camp Attendee Tim Stowell and his family were skeptical of the camp, but desperate enough to give it a try.
"I went to the camp somewhat optimistic, but also doubtful," Mr. Stowell said. "Camp ended this past Saturday and I am still dumbfounded at the change it has wrought on our family's life. Never in my wildest dreams could I have believed this possible in so short a time."
To read more firsthand accounts from other attendees, visit Turning Point Camp's website.
The next Turning Point Camp will be held at Fort Bluff Camp in Dayton on March 9-15, 2014, and is sponsored by Advanced Parents Stepping Up (APSU). Seminars will also be held March 6 and 7, 2014 by highly sought after Author and Therapeutic Parenting Specialist Nancy Thomas. These seminars are available to educators and mental health professionals and may potentially be used as continuing education credits and professional development hours. Turning Point Camp Director Nancy Thomas will also be facilitating the camp.
For more information or to register, visit http://www.turningpointcamp.com/.
June 23, 2016
According to numbers released Thursday by the U.S. Census Bureau, Tennessee's 2015 median age is 38.6 years, slightly older than the U.S. median age, which rose from 37.7 in 2014 to 37.8 in 2015. ... (click for more)
Senate health chairman Lamar Alexander on Thursday said the miraculous eyesight recovery of Tennessean Doug Oliver underscores the need for passage of 21st Century Cures to "unleash medical innovation ... (click for more)
Chattanooga area doctors Justin Calvert of Signal Mountain, Elizabeth Ferluga of Hixson, and Chetan Shah of Hixson are among a group of 12 emerging physician leaders from around the state ... (click for more)
According to numbers released Thursday by the U.S. Census Bureau, Tennessee's 2015 median age is 38.6 years, slightly older than the U.S. median age, which rose from 37.7 in 2014 to 37.8 in 2015. The data release includes national, state and county population estimates for 2015 by age, sex, race and Hispanic origin. A partner to the U.S. Census Bureau, the Tennessee ... (click for more)
Senate health chairman Lamar Alexander on Thursday said the miraculous eyesight recovery of Tennessean Doug Oliver underscores the need for passage of 21st Century Cures to "unleash medical innovation and give more Americans access to life-changing treatments and life-saving cures, like Doug did." Senator Alexander made his remarks at a Bipartisan Policy Center event alongside ... (click for more)
Rather than spend millions upgrading Signal Mountain 's historic grammar school so it can continue to house the Mountain Arts Community Center (MACC), it would make more sense to incorporate that project into a larger multi-pronged one that would solve several issues facing the community, according to town manager Boyd Veal. For example, Mr. Veal said, the current ... (click for more)
Chattanooga firefighters were called to a fire at the city's wood recycling center on N. Hawthorne Street around noon on Sunday. Battalion Chief Don Bowman said the smoke and flames could be seen from several miles away. Firefighters with five fire companies worked to get the blaze under control, using master streams from two aerials and some hand-held hoselines. The ... (click for more)
I am writing this letter to bring to your attention to a city traffic issue that needs to be addressed immediately, the sooner the better. I can see no large cost factor. Recently, while as a concerned citizen, removing trash and litter from the entry/exit area of the Wilcox Tunnel on the side that runs into Chamberlain Avenue, I fully realized that this area could ... (click for more)
Coeur d'Alene, Idaho, is a really cool place. I tried to buy a huge mounted buffalo head in an antique store there one time until I found out the shipping charges were four times what the head was worth. But suddenly my rapt attention is riveted on Coeur d'Alene again because a dazzling social experiment is taking place this very moment at a plush resort in north Idaho. Several ... (click for more)


text:
Relevant offers
Human rights lawyers and campaigners have asked the International Criminal Court (ICC) to investigate allegations of torture by British troops in Iraq, a move which the UK government dismissed as unnecessary.
A Berlin-based human rights group and a British law firm have submitted what they describe as 250 pages of analysis to the ICC's Office of the Prosecutor requesting action on alleged abuses between 2003 and 2008.
The European Centre for Constitutional and Human Rights (ECCHR) and Public Interest Lawyers (PIL) said in a press release posted on the ECCHR website that there had been "systemic abuse" of Iraqi detainees during the British presence in Iraq which met the threshold of war crimes.
An ICC spokeswoman declined immediate comment on the submission.
The ICC, which receives dozens of submissions every year and takes very few of them further, can only act where national jurisdictions are unable or unwilling to investigate alleged crimes.
British Foreign Secretary William Hague said Britain's willingness to investigate the allegations meant action by the ICC was unnecessary.
"The British armed forces uphold high standards ... so we reject any allegations of systematic abuse. But where there are substantiated allegations of things going wrong these things have been or are being investigated," Hague told Sky News.
"That does not require references to the International Criminal Court ... This is being dealt with properly within the United Kingdom through a very detailed and exhaustive process."
The ECCHR and PIL said more than 400 Iraqi former detainees had made allegations of grave mistreatment, of which 85 had been chosen as "representative cases" in the submission to the ICC.
The two organisations said they wanted the ICC to open formal investigations into senior figures at the Ministry of Defence who "knew or should have known of the widespread patterns of abuse, and turned a blind eye to them", and named former Defence Secretary Geoff Hoon.
Hoon could not be immediately reached for comment.
The ministry said alleged abuses had been or were being investigated through the British and European law courts, through public inquiries, in parliament and through a dedicated publicly funded body called the Iraq Historic Allegations Team.
"Should we be approached by the ICC, we will take the opportunity to explain the very extensive work underway to deal with historic allegations of abuse," the ministry said in a statement.
PIL has played a key role in a number of court cases involving alleged British abuses in Iraq.
It has also been instrumental in bringing about several major public inquiries, including the ongoing Al-Sweady inquiry into allegations that British troops executed and tortured Iraqis in the aftermath of a battle in May 2004. That inquiry is due to present its findings at the end of this year.
- Reuters
Sponsored links
Gunmen take guests hostage after car blast at Mogadishu hotel
Two dead, many hurt in US shooting at Texas dance studio
Brexit: Britain's EU commissioner Jonathan Hill resigns following leave vote
Protesters take to the streets to show support for Scotland remaining in the EU
West Virginia death toll at 23 in deadliest US flooding of 2016
Brexit: Newspaper front pages after Britain votes to leave the EU
Fast-moving 'ferocious' California wildfire kills two, destroys homes and vehicles
WATCH: US murder suspect tries to snatch cop's gun inside interview room
Brexit: How the EU split will actually work
Devotees of US motivational speaker burned after walking on hot coals
Boris Johnson: From 'court jester' to Prime Minister-in-waiting
Brexit stuns investors, wipes US$3 trillion off stocks
Search on after man in Australia falls off ferry into freezing waters
Gudni Johannesson: The 'ordinary guy' who will likely be Iceland's next president
Gunmen take guests hostage after car blast at Mogadishu hotel
All Blacks crush Wales to sweep series with six-try win in Dunedin
Two dead, many hurt in US shooting at Texas dance studio
Moko: Hit, kicked, thrown, bitten, stomped and smothered – but prosecutors can't prove couple murdered the boy
Models used in adverts for homeless charity a 'kick in the guts'
Lotto punters strike it lucky - but Powerball still up for grabs
Weird laws still exist in New Zealand - and you could get punished if you break them
Brexit: Newspaper front pages after Britain votes to leave the EU
Two dead, many hurt in US shooting at Texas dance studio
Gunmen take guests hostage after car blast at Mogadishu hotel
Powerful NZ dame: UK ties to become deeper, stronger and more significant
Why corporates are splashing out on lavish reward trips down under
5 things to do if you don't like skiing or snowboarding
Tourist hotspots: Travelling with the wrong crowd
All Blacks crush Wales to sweep series with six-try win in Dunedin
Recap: Wallabies v England - third test in Sydney
82-year-old grandmother rejects $27 million offer so she can stay in her home
High-speed crash kills four near Hamilton, witnesses report 'racing' before impact
All Blacks player ratings: Great night for Barrett, Dagg, Retallick as Welsh swept
England complete 3-0 series sweep of Wallabies in Sydney try-fest
Julian 'The Bus' Savea struggles to hit top gear against Wales
Phil Gifford: All Blacks selections pay off for Steve Hansen and co
All Blacks send Wales packing - now bring on the Aussies in Sydney
Protesters take to the streets to show support for Scotland remaining in the EU


text:
GeForce GTX 1070 2-way SLI review
DeepCool Captain 240 EX review
Palit GeForce GTX 1080 GameRock Premium Edition + G-Panel review
ASUS ROG Strix GeForce GTX 1080 review
Samsung 750 EVO 500GB SSD review
Gigabyte GeForce GTX 1080 G1 GAMING review
MSI GeForce GTX 1070 Gaming X review
Nvidia GeForce GTX 1070 review
GeForce GTX 1070 FCAT Frametime Analysis Review
Guru3D Rig of the Month - May 2016
Jagged Alliance: Back in Action Demo
by Hilbert Hagedoorn on: 02/02/2012 01:34 PM | Source | 0 comment(s)
Kalypso Media and bitComposer Games have released a playable demo for Jagged Alliance: Back in Action, the latest installment in the series developed exclusively for PC. The demo includes one tutorial mission, the Orta Laboratory level which takes place about 2/3 of the way through the game and challenges players to demonstrate their advanced tactical planning skills through the 'Plan & Go' system.
The demo also offers a pre-assembled team of veteran mercenaries, armed to the teeth and ready for action. Jagged Alliance: Back in Action will be launched on February 10th, 2012.
« The Elder Scrolls V: Skyrim - Creation Kit Video · Jagged Alliance: Back in Action Demo · ThermalTake Level 10 GT Call of Duty edition »
Jagged Alliance: Back in Action Video - 01/17/2012 01:30 PM
Here's a series of clips taken from a press preview build of Jagged Alliance: Back in Action which comes out in February 2012. ...
Jagged Alliance: Back in Action video - 12/09/2011 01:17 PM
Here's a new trailer from Jagged Alliance: Back in Action, the upcoming turn-based strategy remake in the works at bitComposer. ...


text:
Search Results for "cluster europe"2 links
- F5LEN Webcluster
- Webcluster F5LEN member of the European DxCluster network.
[ Hits: 18250 | Votes: 347 | Rating: 8.34 ]
- Refractive Index maps for Europe
- Refractive Index maps forecast for Europe
[ Hits: 348 | Votes: 5 | Rating: 6.80 ]
Not satisfied ? Lookup Google Custom Search Engine for cluster europe
cluster europe
Related Searches
You can try similar termscluster europe dx cluster ham dx cluster cluster mbu cluster xd cluster 11m cluster vhf dx cluster us dx cluster cluster to rf my dx cluster dx cluster for mac osx dx cluster for ios cluster dx ah cluster
Get our links, Everywhere!
Follow us on Social Networks
|RSS Feeds
Sign up for daily Newsletter
Service provided by Google FeedBurner
Free for your Site
Add our gadgets to your siteDaily Top 10 links


text:
Winter Dreams (Dodo Press)by F. Scott Fitzgerald
View All Available Formats & Editions
Francis Scott Key Fitzgerald (1896-1940) was an Irish American Jazz Age novelist and short story writer. He is regarded as one of the greatest American writers of the twentieth century. He was the self-styled spokesman of the "Lost Generation" - Americans born in the 1890's who came of age during World War I. He finished four novels, left a fifth unfinished, and wrote dozens of short stories. The 1920's proved the most influential decade of Fitzgerald's development. His debut novel, This Side of Paradise (1920) examines the lives and morality of post-World War I youth. Flappers and Philosophers (1920) was his first collection of short stories. His second novel, The Beautiful and Damned (1922), demonstrates an evolution and maturity in his writing, and provides an excellent portrait of America during the Jazz Age, as does Tales of the Jazz Age (1922). The Great Gatsby, which many consider his masterpiece, was published in 1925. It has since been adapted for the theatre and filmed several times. His last novel was Tender is the Night (1934).
Product Details
- 9781409944201
- Publisher:
- Dodo Press
- Publication date:
- 03/28/2009
- Pages:
- 48
- Product dimensions:
- 6.00(w) x 9.00(h) x 0.12(d)
- Age Range:
- 1 - 17 Years
Customer Reviews
Average Review:
and post it to your social network
Most Helpful Customer Reviews
See all customer reviews >


text:
Author: Thomas W. Nelson (Hodgson Russ LLP, Buffalo)
President Obama's State of the Union address, delivered on January 20, 2015, proposed three significant changes to US federal tax law: (1) an increase from the current 20 percent rate to 28 percent for the top federal capital gains and dividend tax rates applicable to high-income taxpayers (spouses with combined income exceeding about $500,000); (2) a closing of what President Obama called in a January 17, 2015 fact sheet "the trust fund loophole," by which an estate beneficiary enjoys a tax-free basis step-up in inherited property to its FMV at death; and (3) the imposition of a 7-basis-point fee on the liabilities of a large US financial institution whose assets exceed $50 billion (the same benchmark for enhanced supervision of those institutions that was imposed under the 2010 Dodd-Frank Act). It is not clear whether the higher capital gain and dividend rates include the special 3.8 percent net investment income tax already paid by high earners.
The tax-free basis step-up at death was widely seen as a counterbalance to the estate tax on a decedent's assets. However, the US estate and gift tax exemption (currently about $5.3 million for a US citizen and domiciliary and $10.6 million for US-citizen and/or US-domiciliary spouses) reduces or eliminates the estate tax outlay, and to that extent the basis step-up for income tax purposes may be seen as a windfall. (No income tax is ever payable on the appreciation.) President Obama's proposal treats transfers at death (except to charitable organizations) as realization events or deemed sales that give rise to tax on the property's appreciation, similar to the Canadian capital gains tax on death. But the proposal does not modify US estate tax to reflect this change.
Several carve-outs and exceptions are proposed to the new "deemed sale at death" rule, including a carve-out for the transfer of certain tangible personal property and exceptions for a spousal transfer (tax is deferred until the surviving spouse's death), for lower levels of capital gains, and for a personal residence ($500,000 per spouse).The current tax-free stepped-up basis at death is available to a beneficiary of a non-US-citizen Canadian-resident decedent, even though the decedent's estate is not subject to US estate tax on non-US-situs property that passes to the US beneficiary (subject to narrow exceptions—for example, for PFIC shares). A Canadian resident who owns passive assets in a Canadian entity that will pass to a US beneficiary at death is encouraged to use a ULC holdco—not a Canco holdco—so that the step-up applies not only to the entity's shares but also to its underlying assets.
If the US capital gain rate for an individual increases to 28 percent, a Canadian who invests in US property is more motivated to structure the investment to exempt its sale from US tax. The most common structure exempts from capital gain tax the sale of shares of a USco (unless it is a US real property holding corporation under FIRPTA). It is not completely clear whether the gain from the sale of an LLC or an LP interest qualifies for exemption. Revenue ruling 91-32 (1991-1 CB 107) says that the gain should be taxable to the extent that the LLC's or LP's assets are part of a US trade or business, but practitioners have expressed doubt about the ruling's reasoning. President Obama proposes to codify the ruling's principles in the Code, which suggests that the administration also has doubts about the ruling's support in current law.
The proposals are unlikely to be enacted without significant modification. Moreover, since the Republicans took control of both the Senate and the House after the 2014 elections, increased calls have been heard for a sweeping overhaul of the Code; such an overhaul would dwarf the three Obama proposals. The criticisms focus especially on rules that affect businesses' ability to compete in the world marketplace, such as the rule that treats a dividend from a foreign subsidiary to a US parent as a taxable distribution, which has encouraged US multinationals to accumulate offshore billions of dollars of unrepatriated profits and has impelled the current wave of inversion transactions. It is hoped that any serious tax reform that occurs will remedy the inequities that face US citizens resident in Canada. For example, foreign tax credits are denied to US-citizen Canadian residents for the new 3.8 percent net investment income tax. Another example is the overly broad classification rules that determine when a Canco is a PFIC; those rules trap many active Canadian companies, especially those engaged in rental real estate operations.
This article first appeared on ctf.ca.
2016/06/282016 SARS Webinar: 12:30pm - 14:30pm session: Filing Season 2016 - 28 June
2016/06/282016 SARS Webinar: 15:00pm - 17:00pm session: Filing Season 2016 - 28 June
2016/07/122016 VAT Fundamentals - Johannesburg
2016/07/132016 BDO: Transfer Pricing Workshop - Johannesburg
2016/06/24Illogical red tape keeps fuel rebates off limits for outsourced firms
2016/06/23Individual Taxpayers no longer able to make changes or updates to prepopulated IRP5
2016/06/23Time for taxpayers to start preparing for filing season
2016/06/22Tax Season 2016 for Individuals
Section 240A of the Tax Administration Act, 2011 (as amended) requires that all tax practitioners register with a recognized controlling body before 1 July 2013. It is a criminal offense to not register with both a recognized controlling body and SARS.
The Act requires that a minimum academic and practical requirments be set to register with a controlling body. Click here for the minimum requirements of SAIT.


text:
V.22 No.4 | 1/24/2013
With this dulcimer, I thee rule!
By Carl Petersen [ Sat Jan 19 2013 1:03 PM ]
Dear Diary: Today I tried to learn to play the dulcimer. I couldn't do it because I am stupid. However, Alibi superstar designer Jesse Schulz made me this picture of a deadly warlord holding a dulcimer. The warlord's girlfriend looks like a handful.
Today's Events
What Are Fractals? at Greater Albuquerque Habitat for Humanity ReStore
Learn about fractals through presentations and hands-on activities.
Dueling Piano Show • Jorge Ramirez • Brian Burtless • Valerie Gabriel • piano at Uptown Funk Dueling Piano Bar
Near North Valley Neighborhood Association Annual Meeting at Indian Pueblo Cultural CenterMore Recommended Events ››
Kombat Kitty @ Barley Rm • 7.1.2016
home | feature | news | film | music | art | food | classifieds | personals | staff | lo-fi | search
© 1996-2016 Weekly Alibi firstname.lastname@example.com
View mobile version


text:
Coyotes Find Location For New Arena AEG Proposes New Arena In San Diego Vegas NHL Team Sets Sights On Practice Facility Cowboys Open New Restaurant In AT&T Stadium Colorado Looks To Monetize Facility Upgrades Panel Wants To Reduce Funding For Vegas Stadium Judge Rules In Vikings' Favor In Wells Fargo Dispute Falcons' McKay Confirms $200M Changes To Stadium Penn State's Beaver Stadium Likely To Renovate Facility Notes
Upcoming Conferences and Events
SBD/December 5, 2012/Facilities
Facility Notes
Published December 5, 2012
ON THE PROWL: In Phoenix, Kent Somers reports the NFL Cardinals' contract with Northern Arizona Univ. "has ended, and it's possible the team's history of training in Flagstaff is over, too." The Cardinals are "exploring several options, including returning to NAU, where they've trained every year but one since moving to Arizona in 1988." The team has become "disenchanted with its arrangement with NAU, especially in terms of the facilities." Team execs "continue to meet with officials from NAU and Flagstaff but have opened bidding for other cities" (ARIZONA REPUBLIC, 12/5).
SERVING ALL: In Boston, Ira Kantor notes animal advocacy group PETA ranks Gillette Stadium No. 2 on this year's list of "vegetarian-friendly" NFL stadiums. The group "specifically called out such menu options as black bean burgers, grilled portobello mushroom burgers and grilled veggie flatbread wraps." Gillette Stadium Senior VP/Operations, Administration & Finance James Nolan said, "We wanted the new menus to reflect the changing taste of our guests." Gillette Stadium took second place behind the Eagles' Lincoln Financial Field (BOSTON HERALD, 12/5).


text:
Comments On This Things You Think Only You Do
- It actually worked this time I got this Minecraft Premium Code and it got accepted! If you need a code check out http://freeminecraft.?? Read more at http://freeminecraft.us/#qtFIv8sf1L7vjqYJ.99
A collection of things you think only you do. Go ahead and confess. You probably aren't the only one.
"Roses are red Violets are blue Get in the car I want to **** you."
via: Anti-Pickup Line
"LOTUS - Lots Of Trouble, Usually Serious.."
via: Clarksonisms
via: Pointless Inventions
"The kind of power Mel GIbson had in "What Women Want"."
©2008-2014 Things You Think Only You Do. All rights reserved.
A Horse Head Huffer Production.
Rails Hosting provided by BlueBox