Chapter 5 – TCP/IP: Routing – Part 2 Dr. V.T. Raja Oregon State University

TCP/IP – Routing - Part 2 Outline Routing Protocols Unicast messages Broadcast messages Routing Tables

Autonomous System of Networks Routing Protocols Autonomous System of Networks Each large organizational network connected to Internet (e.g., AT&T, IBM, OSU) can be viewed as a separate autonomous system Computers within each autonomous system usually exchange routing information among themselves Routing protocols used inside an autonomous system are called interior routing protocols Routing protocols used between autonomous systems are called exterior routing protocols

Routing Protocols Internet Control Message Protocol (ICMP) –Error advisement Example: Ping command – Host (Destination) unreachable –Flow control Requesting a device to reduce the rate at which it transmits

Routing Protocols Routing Information Protocol (RIP) –Dynamic distance vector routing protocol –Scalability: 15-hop limit –Good for smaller networks –Broadcast interruptions (entire routing table transmitted very often) –Slower convergence – Takes a longer time for routing tables to be transmitted very often

Routing Protocols Open Shortest Path First (OSPF) –Link State Dynamic Routing Protocol –Faster convergence Designated router updated on changes in route status Border Gateway Protocol (BGP) –Distance Vector Dynamic Routing Protocol –Used between autonomous systems –Changes in route status info transmitted

Comparison of Routing Protocols RIPOSPFBGP Interior/Exterior? Interior Exterior Type (Distance Vector/ Link State?) Distance VectorLink StateDistance Vector Routing update content (Routing Table/Updates?) Routing TableUpdates only Routing update frequency Very often (e.g., every 30 seconds) Updates only Convergence (Slow/Fast/Complex?) SlowFastComplex Scalability PoorVery Good

TCP/IP and Routing TCP/IP can use RIP, ICMP, OSPF, BGP It is compatible with distance vector and link state protocols Can operate either as connectionless or connection oriented routing Can support QoS routing (a new version of OSPF called QOSPF)

Unicast/Broadcast Unicast –Most common type of message transmitted (from one sender to one final destination) –Example: Broadcast –Subnet broadcast Example –LAN broadcast Example

Routing Tables Routing Table for B DestinationRouteAC DAE FE GC DefaultA

Routing Table (Continued) Network Destination NetmaskGatewayInterfaceMetric (Cost) Default route: Loop back (Self) Network Route Local Host Subnet broadcast Multicast: Broadcast

Introduction Router Forwarding Table Destination AddressPrefix (Mask)Metric (Cost)InterfaceNext-Hop Router ( )472G H F H Local H