~~~~ethernet 基础.ppt

IEEE 802.1p Priority Bit Setting and Queuing MPLS - Domain MPLS - Example IGMP Snooping IP/MPLS Voice ISPs ASPs  DSLAM/Switch is reading all data frames and interprets IGMP messages By evaluating IGMP joins and IGMP query reports, the DSLAM can  recognize which multicast group can be reached via which DSL port IGMP messages listening to the IGMP conversation between router and hosts Fig. 31 IGMP Snooping (, 45) IGMP Proxy hiX DSLAM Fig. 32 IGMP Proxy (, 45) Interior and Exterior Routing An Autonomous System (AS) is a collection of routers with a single  coherent interior routing plan Interior routing protocol (IGP) is run inside an autonomous system resulting in optimum intra-AS routing Exterior routing protocol (EGP) is run between autonomous systems to enable routing policies EGP IGP AS 1 AS 2 IGP BGP RIP/OSPF RIP/OSPF Fig. 33 Interior and Exterior Routing (, 47) Routing Information Protocol (RIP) Interior Routing Protocol suitable for small-seized networks RIP uses the Distance Vector Algorithm Hop-Count is being used as metric (max. number of hops: 16) RIP messages are being distributed via broadcasts RIP but doesn‘t scale very well in large enterprise networks Routing loops may occur RIP has slow convergence times (n * 30 sec) RIP Version 2 has been developed to overcome  the limitations of version1 SUMMARY: - RIP is a ?low-brainer“  - RIP is suitable for small networks Fig. 34 RIP (, 49) Open Shortest Path First (OSPF) Interior Routing Protocol suitable for medium-seized  and larger networks fast convergence time (in comparison to RIP) supports VLSM (Variable Length Subnet Mask) metric based on link bandwidth efficient use of the bandwidth for updates supports several routes to the destination (redundancy) allows hierarchical networks (based on areas) SUMMARY: - OSPF scales better than RIP - but some administration work to do (area config) Fig. 35 OSPF (, 49) Border Gateway Protocol (B