interdomain routing

What is an autonomous system?

Internet is so large that no one routing protocol can handle the task of updating the routing tables of all routers. Internet is divided into autonomous systems.

An autonomous system is a group of networks and routers under the authority of a single administration.

Routing inside an autonomous system is referred to as intra-domain routing. Routing between autonomous systems is referred to as inter-domain routing.

What is interdomain routing?

The interdomain routing involves AS sharing their reachability information with each other AS.

The goal of interdomain routing is reachability and not optimality.

The two major interdomain routing protocols are Exterior Gateway Protocol (EGP) and Border Gateway Protocol (BGP).

What are the problems in interdomain routing?

An internet backbone must be able to route packets to any destination, i.e., there should be a match in the routing/forwarding table.

Each AS has its own intradomain routing protocols and chooses the metric assigns to path. This varies from one AS to another.

Autonomous systems may not trust each other.

Write short notes on BGP.

Border Gateway Protocol (BGP) is an inter-domain routing protocol using path vector routing

Traffic on the internet can be classified into two types:

o   local traffic that starts/ends on nodes within an AS

o   transit traffic that passes through an AS AS can be classified into three types

o   Stub AS has only a single connection to one other AS. This AS can carry local traffic only, such as Small corporation.

o   Multihomed AS has connections to more than one other AS but refuses to carry transit traffic, such as Large corporation.

o   Transit AS has connections to more than one other AS and is designed to carry both transit and local traffic, such as the backbone providers

Each AS selects one of its nodes to be the BGP speaker.

Speaker node creates a routing table for that AS and advertises it to other BGP speakers in the neighboring ASs.

State the drawbacks of IPv4?

Despite all short-term solutions, such as subnetting, classless addressing, and NAT, address depletion is still a long-term problem in the Internet.

The Internet must accommodate real-time audio and video transmission that requires minimum delay strategies and reservation of resources, which are not provided in IPv4.

The Internet must provide encryption and authentication of data for some applications. No encryption or authentication is provided by IPv4.

How NAT helps to solve address space depletion?

The idea behind Network Address Translation (NAT) is that all hosts that uses Internet do not need to have globally unique addresses.

NAT enables a organization to have a large set of addresses internally and one address or a small set of addresses externally.

Three  sets  of  addresses  are  reserved  for  internal  use  (10.0.0.0 –  10.255.255.255,

172.16.0.0 – 172.31.255.255 and 192.168.0.0 – 192.168.255.255).

The organization must have only one single connection to the Internet through a router that runs the NAT software.

Briefly explain IGMP?

Internet Group Message Protocol (IGMP) is a protocol that manages group membership. Provides the multicast routers information about the membership status of hosts (routers)

connected to the network.

Enables a multicast router to create and update list of loyal members related to each router interface.

The operations are:

o Joining a group

o Leaving a group

o  Monitoring membership