Ch. 8 Routing
1. What is routing?
Routing is the process of moving information from the source network to the destination network through intervening LANs and WANs. Routing involves the selection of paths between the two networks.
9. What are routing protocols?
Routing protocols are the mechanism used by routers on the Internet to maintain routing tables. Routers use routing protocols to communicate route information with neighboring routers.
3. What are the important similarities between switching and routing?
Both switches and routers are used to deliver data from a source to a destination.
6. What is a routing table? What information is stored in a routing table?
A routing table is a collection of paths that can be reached from the router along with information about the path. Each entry in the routing table lists a network that can be reached, the neighboring router to forward the packet to in order to reach this network, and details about the path to the destination through this neighbor
LANs use broadcasting to ensure that data reaches its destination. Why is it not advisable to use broadcasting between LANs?
Broadcasting within the LAN only creates a limited amount of unnecessary traffic. Broadcasting data between LANs would generate too much unnecessary traffic. This traffic volume would overwhelm routers and end user computers.
4. What are the important differences between routing and switching?
Switches are used within LANs, whereas routers are used across LANs. Therefore, switches use MAC addresses whereas routers use IP addresses. Switches deliver data from a host to another host. Routers deliver packets from a source network to a destination network. Switches typically cannot handle loops within networks; whereas routers can handle any network layout. Switches typically configure themselves, whereas routers require administrative support for configuration.
5. Briefly describe how routing works.
The Internet is organized as a collection of autonomous systems. Routers connect autonomous systems to one another. Routers maintain a routing table which aggregates information about all known paths between autonomous systems. Routers also periodically exchange information about these routes with each other, informing other routers about known changes to these paths so that other routers can update their routing tables. When a packet arrives at a router, the router looks at its routing table to identify the best neighboring router to forward the packet to. The neighboring router then identifies the next best neighbor and so on, until the packet reaches its destination autonomous system. At the destination AS, the network uses whatever technology is available to direct the packet to the destination host
What is a routing metric? How is the routing metric used to select the path when multiple paths are available?
The routing metric for a network path is a measure of the cost of delivering a packet through the path. When choosing among multiple paths to deliver a packet, routers select the path with the lowest metric.
What are the two kinds of routing protocols? Give an example of each of the two kinds of routing protocols.
There two kinds of routing protocols - exterior and interior. An example of an exterior routing protocol is the Border Gateway Protocol, or BGP. An example of an interior routing protocol is Open Shortest Path First protocol, or OSPF.
Use the tracert utility to record the route from your home computer to your university's home page.
USF has locked down its router to block ICMP packets. I therefore performed a tracert to FAU. (Image, tracert www.fiu.edu)
11. Provide an overview of how exterior routing protocols work.
n exterior routing protocols, each router informs its immediate neighbors about the networks it can connect to. Routers collect this information from all their neighbors and pass this information on to their neighbors. This way information about available routes reaches all routers on the Internet.
