Chapter 5 TCP/IP: Routing – Part 1 Dr. V.T. Raja Oregon State University
TCP/IP – Part 4 - Routing Outline Part 4a: Introduction Different Types of Routing Part 4b : Routing Protocols Routing Tables
TCP/IP-Part 4a: Routing Routing : Path taken by message from sender to final destination Routing Table : Devices that perform routing have a routing table that specifies route to different destinations. The routing tables are constructed/updated using different types of routing technique(s). Different Types of Routing –Centralized –Decentralized Static Dynamic Routing (Distance Vector and Link State Dynamic Routing) – Connectionless and Connection-Oriented Routing – QoS Routing
Centralized and Decentralized Routing Different Types of Routing Centralized and Decentralized Routing Centralized Routing –All routing decisions are made by one central computer –Example: Decentralized Routing –Computers/routers in network make their own routing decisions following a formal routing protocol, which could be capable of self-adjusting, and adapting to changes in the network configurations
Static Routing Different types of Routing Decentralized Routing: Static Routing Static –Routing table is developed by the network manager –Changes are made to the routing table only when computers are added or removed from network –Example:
Dynamic (Adaptive) Routing Different types of Routing Decentralized Routing: Dynamic (Adaptive) Routing Dynamic Routing –Used when there are multiple routes and it is important to select the best (or fastest) route, in order to route messages away from traffic on busy circuits –An initial routing table is developed by the network manager, but is continuously updated by the computers themselves (with the help of routing protocols) to reflect changing network conditions, such as network traffic
Distance Vector Dynamic Routing Different types of Routing Decentralized Routing – Dynamic (Adaptive) Routing Distance Vector Dynamic Routing Distance Vector Dynamic Routing –Routing decisions are made based on # of hops along a route –What is a hop? Examples: –A - C (via B): »# of hops = –A – C (via D, E & F): »# of hops = –Computers periodically (could be as often as every 1-2 minutes) exchange information on the hop count and sometimes the relative speed of the circuits in route with their neighbor
Link State Dynamic Routing Different types of Routing Decentralized Routing – Dynamic (Adaptive) Routing Link State Dynamic Routing Link State Dynamic Routing –Routing decisions are based on several factors: Number of hops in each route Speed of circuits in each route Traffic conditions on each route (How busy the route is?) Reliability of each route
Disadvantages of Dynamic Routing Requires more processing effort from each computer on the network compared to centralized or static routing “Compromises” on network capacity during transmission of route status information
Connectionless and Connection-Oriented Routing Different Types of Routing Connectionless and Connection-Oriented Routing A message may be segmented into several packets Connectionless Routing –Different packets of the same message could take different routes Connection-Oriented Routing –A virtual circuit (VC) is set up between sender and receiver –A VC is one that appears to be a point-to-point circuit –All packets follow the same VC route; –Overhead involved in establishing and closing VC before and after transmission of all packets
Quality of Service (QoS) Routing Different Types of Routing Quality of Service (QoS) Routing Quality of Service (QoS) Routing –Special type of connection- oriented dynamic routing protocol –Different messages or packets are assigned different priorities Applications: –Different classes of service are defined for different priorities Example: