N - Multilateral Planners Conference

UNCLASSIFIEDACP 200(B) Vol 1ROUTING235. An MTWAN may comprise one or more Autonomous Systems (AS). Open ShortestPath First (OSPF) and Protocol Independent Multicast (PIM) will be used for interior routingwithin an Autonomous Systems (AS) and Border Gateway Protocol (BGP4) for exteriorrouting between AS. Figure 2-7 depicts a single-AS MTWAN that is divided into a number ofOSPF areas. LAN-to-LAN connectivity is provided by the backbone subnets. Details onMTWAN routing can be found in Chapter 15.COMMUNICATION SUBNETS236. As shown in Figure 2–7, sending information to a destination on a different LAN,which is itself a subnet, will rely on the forwarding service provided by routers. The routersare connected to each other via MTWAN subnets and each is supported by a communicationcircuit. Some communication subnets, such as those supported by UHF LOS, HF, and UHFSATCOM require special equipment to interface communication systems to the routers.Details on the communication subnets can be found in Chapter 16.TRANSPORT SERVICES237. Most end-user applications use Transmission Control Protocol (TCP) as the transportlayer protocol. However, TCP can perform poorly over satellite and multi-member subnetsdue to long delay and large jitter. As a result, utilization of available bandwidth byapplications can be low. Some form of TCP Proxies can be used to improve data throughputfor applications over the available communication bandwidth. Multicast (one-to-many) canprovide an alternative solution for an efficient use of bandwidth. Studies have shown thatmany information transfers within a MTWAN are multicast in nature and this can save asignificant amount of available bandwidth. Details on Transport Services can be found inChapter 13.Uncontrolled copy when printed2-12UNCLASSIFIEDOriginal