RD-CSY3021 Comparing Routing Protocols. RD-CSY3021 Criteria used to compare routing protocols includes Time to convergence Proprietary/open standards.
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Presentation on theme: "RD-CSY3021 Comparing Routing Protocols. RD-CSY3021 Criteria used to compare routing protocols includes Time to convergence Proprietary/open standards."— Presentation transcript:
RD-CSY3021 Criteria used to compare routing protocols includes Time to convergence Proprietary/open standards Scalability Classful/Classless Metric used Resource usage Implementation & maintenance
RD-CSY3021 Two Main Approaches Distance Vector Protocols ◦ E.g., RIP V1 and v2 (Routing Information Protocol) ◦ EIGRP Link State Protocols ◦ E.g., OSPF (Open Shortest Path First) Our Focus ◦ Comparing them
Classful vs. Classless Routing Behavior -It is recommended to use classless routing behavior Reason: so supernet and default routes can be used whenever needed
Classless Routing Protocol Routing updates include the subnet mask Supports VLSM Supports Route Summarization
RD-CSY3021 Algorithm - procedure for accomplishing a certain task
Link State (LS) advantages: More stable (aka fewer routing loops) Faster convergence than distance vector Easier to discover network topology, troubleshoot network.
Uses hop count as metric (max: 16 is infinity) Tables (vectors) “advertised” to neighbors every 30 s. Each advertisement: upto 25 entries No advertisement for 180 sec: neighbor/link declared dead routes via neighbor invalidated new advertisements sent to neighbors (Triggered updates) neighbors in turn send out new advertisements (if tables changed) link failure info quickly propagates to entire net poison reverse used to prevent ping- pong loops (infinite distance = 16 hops)
Split horizon/poison reverse does not guarantee to solve count-to-infinity problem ◦ 16 = infinity => RIP for small networks only! ◦ Slow convergence Broadcasts consume non-router resources RIPv1 does not support subnet masks (VLSMs) ◦ No authentication
Why ? Installed base of RIP routers Provides: ◦ VLSM support ◦ Authentication ◦ Multicasting Uses reserved fields in RIPv1 header. Supports authentication.
Key: Create a network “map” at each node. 1. Node collects the state of its connected links and forms a “Link State Packet” (LSP) 2. Flood LSP => reaches every other node in the network and everyone now has a network map. 3. Given map, run Dijkstra’s shortest path algorithm (SPF) => get paths to all destinations 4. Routing table = next-hops of these paths. 5. Hierarchical routing: organization of areas, and filtered control plane information flooded.
Reliable Flooding: sequence #s, age Neighbor discovery and maintenance (hello) Efficiency in Broadcast LANs ◦ designated router (DR) concept Areas and Hierarchy ◦ Area types: Normal, Stub, NSSA: filtering ◦ External Routes (from other ASs), interaction with inter-domain routing.
Information hiding (filtered) => ◦ less computation, => less bandwidth requirement => Less storage => Improved efficiency => leads to scalable networks
Two-level hierarchy: local area, backbone. Link-state advertisements only in area each nodes has detailed area topology; only know direction (shortest path) to nets in other areas. Two-level restriction avoids count-to-infinity issues in backbone routing. Area border routers (ABR): “summarize” distances to networks in own area, advertise to other Area Border routers. Backbone routers: uses a DV-style routing between backbone routers Boundary routers connect to other ASs (generate “external” records)