h they charge a hefty premium. These plans allow the customer to send and receive unplanned traffic peaks without packets being dropped. An IIC might also assign higher QoS priorities to certain customers' traffic, making sure for example, that a Fortune 1000 company gets its videoconferences at the expense of a dropped packet or two from a teen IP-voice line. QoS and SLAs QoS is often a major component of service level agreements (SLAs). SLAs are contracts IICs offer to major customers to provide certain guarantees on network performance, traffic delivery and quality. Generally, falling short of a contracted SLA means the IIC owes its customer a discount, rebate or free usage of some kind. In an IP network that carries voice, data and video traffic, QoS is tied closely to traffic type. Voice conversations require guaranteed, two-way bandwidth with almost no delay; they therefore, require a high level of QoS. E-mail, on the other hand, can essentially trickle across a network. As long as it can be reconstructed at the receiving end, it does not matter in what order the packets arrive or how closely together. Thus, e-mail requires a low QoS, or none at all. A live videoconference, like a voice call, requires a high level of guaranteed, multi-directional bandwidth. High QoS. Entertainment video, such as a digital movie rental downloaded to a local cache before viewing, can tolerate more delay, though it will use a lot of bandwidth as it travels across a network. Such a service might require an intermediate level of QoS. Technologies exist today, although they are not widely deployed, that can allow a customer to assign specific QoS to a particular session or call. A call to a friend may not need to be crystal clear, SO it does not need a high cost, high level QoS guarantee as does a call to close a multi-million dollar sale. Billing vendors are continuously refining their rating engines to account for more QoS variations, providing customers with more options and enabling more customized, sophisticated SLAs. NETWOR