Service Classes and Reservation Styles

PROBLEMS 179 • RSVP HOP • TIME VALUES • EXPLICIT ROUTE optional • LABEL REQUEST • SESSION ATTRIBUTE optional • POLICY DATA objects optional • A sender descriptor consisting of the SENDER TEMPLATE and the SENDER TSPEC • ADSPEC optional • RECORD ROUTE optional The RSVP-TE Resv message consists of the common header shown in Figure 7.20 followed by the objects: • INTEGRITY optional • SESSION • RSVP HOP • TIME VALUES • RESV CONFIRM optional • SCOPE optional • POLICY DATA objects optional • STYLE • A style-dependent flow descriptor list. For the fixed-filter FF style, it consists of the objects: FLOWSPEC, FILTER SPEC, LABEL, RECORD ROUTE optional. For the shared explicit SE style, it consists of the objects: FILTER SPEC, LABEL, RECORD ROUTE optional.

7.4.4 RSVP-TE Extensions

RSVP was designed to support resource reservations for data flows defined between a sender and a receiver. As the number of data flows increases, the RSVP overhead on the network increases as well due to the continuous refreshing messages that have to be exchanged. Also, the memory required to store the path state information in each router and the amount of processing increases as well. In view of this, RSVP is not considered a protocol that scales up well. Similar problems arise in RSVP-TE, since it is based on RSVP. Several solutions have been proposed to alleviate these problems. For instance, a mech- anism for reliable delivery has been proposed that reduces the need for refresh messages. This mechanism makes use of two new objects, MESSAGE ID and MESSAGE ID ACK. Also, the amount of data transmitted due to refresh messages can be reduced by using the Srefresh message, a new summary refresh message. PROBLEMS 1. In LDP the hallo adjacency as well as the session have to be continuously refreshed. Since the hallo adjacencies in a session are continuously refreshed, why is there a need to also refresh the session? 2. Explain the need for loosely explicit routes in CR-LDP. Give an example of an application that requires pinning. 180 LABEL DISTRIBUTION PROTOCOLS 3. Could CR-LDP work using unsolicited downstream label allocation and independent order? Why? 4. Consider the traffic parameters for the delay sensitive service class given in Table 7.1. Do these parameters suffice to provide this service? What additional mechanisms is are required? 5. Explain why in RSVP the Path message contains the RSVP HOP object. 6. Explain the difference between the fixed-filter style and the shared explicit style. 7. Is it possible for RSVP-TE to set up a CR-LSP based on the next hop routing information? How? 8. Compare CR-LDP with RSVP-TE. What are the common features in these two protocols? Identify some of the main differences in these two protocols.