chap04 - Cisco Router Handbook Sackett $70.00 98-7 Backward...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Cisco Router Handbook Sackett $70.00 0-07-058098-7 Backward Forward Chapter: 1 | 2 | 3 | 4 | 5 | 6 _________________________________________________________________ Chapter Four IP Routing Protocol Design Routing is the process of moving packets from one network to another. The routing decision takes place at the source network device. That is a router. The decision is made based on metrics used for a particular routing protocol. Routing protocols may use some or all of the following metrics in determining the best route to a destination network: * Path length * Reliability * Delay * Bandwidth * Load * Communication cost Path length is measure in either a cost or a hop count. In link-state routing protocols, the cost is the sum of the costs associated with each link in the path. Distance-vector routing protocols assign a hop count to the path length, which measures the number of routers a packet traverses between the source and destination. Reliability is typically the bit-error rate of a link connecting this router to a source or destination resource. For most of the routing protocols, the reliability of a link is assigned by the network engineer. Since it is arbitrary it can be used to influence and create paths that are favorable over other paths. The delay metric is an overall measurement of the time it takes for a packet to move through all the internetworked devices, links and queues of each router. In addition, network congestion and the overall distance traveled between the source and destination are taken into consideration in evaluating the delay metric value. Because the delay value takes into account many different variables, it is an influential metric on the optimal path calculation. Using bandwidth as a metric in optimal path calculations may be misleading. Though bandwidth of a bandwidth of 1.54 Mbps is greater than 56 Kbps, it may not be optimal due to the current utilization of the link or the load on the device on the receiving end of the link. The load is a metric that assigns a value to a network resource based on the resources overall utilization. This value is a composite of CPU utilization, packets processed per second, and disassembly/reassembly of packets among other things. The monitoring of the device resources itself is an intensive process. In some cases, communication lines are charged based on usage versus a flat monthly fee for public networks. For example, ISDN lines are charged based on usage time and potential the amount of data transmitted during that time. In these instances, communication cost
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
becomes an important factor in determining the optimal route. In designing a routing protocol based network the routing algorithm should have the following characteristics built into the design: Optimality - using some or all of the metrics available for a routing protocol in order to calculate the optimal route. Different routing protocols may apply one metric as having a higher weight to the optimal route calculation than another has. An understanding of this
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 08/08/2011 for the course CS 640 taught by Professor Anbarasu during the Spring '11 term at Anna University Chennai - Regional Office, Coimbatore.

Page1 / 9

chap04 - Cisco Router Handbook Sackett $70.00 98-7 Backward...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online