Router Routes Packets example essay topic

Routers 1 Routers 2 Introduction The purpose of this paper is give a summary of the function and use of Routers in today's information age. To cover the complete subject of routers and routing, would be beyond the scope of this research paper. However the basic definition of a router is " A device used to connect networks of different types, such as those using different architectures and protocols. Routers work at the Network layer of the OSI model. This means they can switch and route packets across multiple networks. They do this by exchanging protocol-specific information between separate networks.

Routers determine the best path for sending data and filter broadcast traffic to the local segment". (Microsoft Press, 1998) Discussion In order for information to pass fro one information system to another information system outside its local area it must be routed. In the below table is an illustration of a the route a data packet takes between my computer and the Web Server for Macon State College. Tracing route to web [168.16.

176.4] over a maximum of 30 hops: Routers 3 TABLE 11 10 ms 10 ms 10 ms 10.10. 10.252 10 ms 10 ms 10 ms 10.10. 100.23 10 ms 10 ms 16 ms 10.10. 14.554 10 ms 15 ms 16 ms 10.10. 11.555 15 ms 63 ms 16 ms 216.46.

52.56 32 ms 47 ms 46 ms c 7513. vldsgacbds 0-1. Hss i 2-0-0. near. ptp. optilinkcomm. net [216.128. 201.5] 7 62 ms 47 ms 94 ms c 7513. vldsgacbds 0-1. ATM 3-0-0-2. far. ptp. optilinkcomm. net [216.128.

201.38] 8 78 ms 94 ms 78 ms Serial 2-7. GW 4. DCA 1. ALTER.

NET [157.130. 43.205] 9 94 ms 62 ms 79 ms 522. at-2-0-0. XR 1. DCA 1.

ALTER. NET [152.63. 37.70] 10 63 ms 94 ms 78 ms 195. ATM 6-0. BR 2.

DCA 1. ALTER. NET [152.63. 36.93] 11 63 ms 94 ms 109 ms t 3-0-0-0. pr 1. Washington 1. DC. us. netrail. net [205.215.

1.13] 12 1938 ms 1859 ms 1891 ms POS 6-1. tr 2. Atlanta 1. GA. us. netrail. net [205.215. 63.14] 13 1859 ms 1907 ms 1875 ms 205.215. 60.19714 94 ms 94 ms 94 ms Peach net-655 M. Atlanta 1.

GA. us. netrail. net Routers 415 78 ms 109 ms 94 ms 131.144. 200.616 109 ms 94 ms 78 ms UD-MAC-MAC. Link. Peach. NET [131.144.

102.226] 17 94 ms 94 ms 109 ms 168.16. 128.21418 94 ms 94 ms 109 ms web [168.16. 176.4] As can be seen in the above table it took 18 hops or to reach Macon. State. edu, this is referred to as the Metric count. If you will examine metrics one thru five you will notice that it took five hops just to leave my local area network. It is amazing to follow the route and see that my packet went all the way to Washington D.C. before it arrived at Macon State's web server.

All along the way decisions were made on how to route the packet based on it's IP address. (Todd Lammle, 1998) A I. P address is a logical 32-bit address used to identify a IP host. Each IP address has two parts: the network ID and the Host ID. The network Id identifies all hosts that are on the same physical network. For example, in Table 1, you can see that the first IP address was 10.10. 10.25, that is the address of my default router.

My router took a look at 168.16. 176.4 (the IP of the Macon State Web Server) and new it was not on the local network. It then sent it across it's Wan link (10.10. 100.2) to it's default router Routers 510.10.

14.55. Then router 10.10. 14.55 looks at the package and recognizes it is not for it's local network, send it to 10.10. 11.55 which is a multi-homed NT firewall.

The firewall accepts the protocol and allows the packet to leave the border router 216.46. 52.5 to begin it's journey to the Macon State Web site. All this happens in time that is measured in Milliseconds. (Matthew Rees, 1999) Routers build what are known as routing tables as they pass packets along. These tables contain the information that allows a router to look at destination address and make a decision on where to forward that packet. The majority of routing tables are built using dynamic protocols, which learn routes from neighboring routers.

However for security purposes an administrator may build static routing tables. This can be a time consuming process and may be prone to errors or failures if a route changes. Some examples of routing protocols are as follows. Routing Information Protocol (RIP) - is a distance vector protocol that uses the metric count to route packets.

It's largest draw back is that is limited to a 15 metric hop count. If you refer to table 1 you can see that if RIP had been used our packet would have timed out before it's arrival. Other protocols such as IGRP (interior gateway routing protocol) and OSPF (open shortest path first) have over come the 15 metric hop count limit used by RIP and use various methods to calculate the best path to route a data packet. Another group of protocol's called EGP (exterior gateway Routers 6 protocols and BGP (border gateway protocols) are used for the large backbone routers that connect many of our major internet backbones. As you can see below in this picture of Verio's U.S. backbone.

It is Vital that up to date tables be kept in order for data to reliably be transmitted from one point to another. (web) Routers 7 As mentioned above routers rely on address that are on layer 3 of the OSI reference model. Layer-3 address appears in the layer-3 header built during the encapsulation process. The layer-3 address is the one that a router uses to perform path determination for those protocols being routed. Not all protocols have an address at layer 3; those protocols that don't have layer-3 addresses are not rou table. A good example is the Net bui protocol.

An address at layer 3 consists of two parts: network and node. The network part is the LAN or WAN address. The node part is the address of the host that is attached to the LAN or WAN indicated in the network part of the address. Consider a building's address consisting of a number and a street name, for example, 1600 Downing Street. The street where the building stands has a name; the street name must be unique in the city.

The building has a number; the number doesn't have to be unique in the entire city; it has to be unique only on the street. Think of the street as the network (LAN or WAN), and the building as a node (device) on the network. A network address must be unique in an internetwork, but the node part of the address needs to be unique only on the network. The full host address is the combination of the network part and the node part of the layer-3 address. A host address must be unique in an internetwork. The network and node parts of a layer-3 address are normally separated by a period ('. ' ) when they are written.

The period is verbally communicated with the word 'dot. ' For example, the IP address 172.16. 126.99 would be pronounced, '172 dot 16 dot 126 dot 99. ' Router 8 Each protocol that has layer-3 addressing can be routed. A router bases its path determination on the network portion of the destination address in the layer-3 header. Each protocol capable of being routed (a routed protocol) has a different format for its layer-3 address.

(Albritton, 1999) I have given a brief overview above of the basics of how a router routes packets across the internet and within an intranet. However I have not discussed exactly what a router is, in relation to the hardware and operating systems involved. Many company's make Routers. Bay, 3 com, Linksys, SMC and Cisco just to name a few. However Cisco is the dominate player in the market so lets look at the basic components of a Cisco router as they relate to hardware.

As you will see they are very similar to a regular computer in many ways. In fact a standard P.C. running Windows N.T. Server can do routing on a small level. The basic internal parts are the processor, RAM, ROM, and NVRAM. Basically the processor performs the calculations necessary to run the router.

The ROM (Routers 9 Read only Memory) is where the operating system is stored. This is flash able meaning it can be upgraded. The NVRAM (non-volatile ram) I where the router-configuration files are stored. This memory will be retained even if the memory is lost. Also externally many different port configurations are available to meet the demands of the end user. (Lammle, 1999) Summary and Conclusion The explosive growth of the internet over the past 10 years has fostered an almost equally explosive growth in the need to transmit data across vast distances quickly and reliably.

Routers have kept pace with this demand. Routers are the traffic cops and road signs that make sure that the email you send to your friend across the country arrives at it's intended destination. I have barely scratched the surface of information that is necessary to keep a enterprise router up and running. As we keep an eye to the future amazing things will continue to un-fold in the world of routers. Routers 10

Bibliography

Lammle, Todd and Porter, Donald. CCNA Study Guide. SYBEX, Network Press 1999 Albritton, John.
Cisco IOS Essentials. The McGraw-Hill Companies 1999 (web) 2001 Microsoft Press.
Networking Essentials Second Edition. 1999.