other hosting node, it would prefer that other hosted node could still reach it by the same network address. If this is supported in networks, network addresses and node names must be kept separate. 3. In traditional public networks, a terminating node can never become a routing node, which assumes that there is always a single operator who operates the routing part of network (and thereby all T-ROs tables). In modern datagram switching networks (such as TCP/IP and MTP L3), the boundary of the routing part of the network is open ended. It allows the switching network to grow with- out central control, and many switching network operators to exist in the same switching network. For example, we can easily imagine node n13 in Fig. 3.24 upgraded from just being a terminating node to a gateway, i.e., a routing node for a large number of hosted nodes (each with its own network address). This would imply that the hosted node n22 could be moved to some hosting node in the new network, the node name of which would not be known by any of the existing switching nodes. The gateway node and the switching network it serves would be operated separately. This is the principle behind how the IP stratum in the Internet is operated, for example, supported by IP addressing methods and separate routing protocols for intra- and inter-network routing. 3.4.3.2 Routes in Circuit-Switching Network Systems There are two categories: systems that switch end-user data (e.g. PSTN and ISDN) and systems that switch data on behalf of such systems. Examples of the latter are PDH and SDH. The former are systems that offer single channel routes with rather low transfer rates (less than 2 Mbps). The latter offer high transfer rate (up to sev- eral Gbps), multichannel routes. PSTN and ISDN realize (primarily) routes on demand by end-users, while PDH and SDH routes are created by control from a management system. In the industry, the term "circuit-switching" is actually reserved for on-demand systems such as PSTN and ISDN, while PDH and SDH are called 