# Homework 7

# 1

## i)

Providing service for free for users who are not part of the customer base is not a desirable choice since it does not make sense to provide a service without some kind of pay.

## ii)

An AS does not does not have to pay its customers for using their routes but it has to pay its providers.

# 2

i) Ingress Traffic Engineering : Inbound traffic engineering is defined as the ways to control the best path going into the router. AS does not have direct control over this.
ii) Egress Traffic Engineering : Outbound traffic engineering is defined as the ways to control the best path going outside of the router. AS has direct control over this.

Egress traffic engineering is usually easier, because the AS has direct control over how it uses the BGP
route attributes to select best next hops for its outgoing traffic, whereas for ingress traffic engineering,
the AS needs to export its routes with attributes that it hope will indirectly influence the neighbor AS’s
route selection in the desired manner.

# 3

This is because without the community attribute, the “highest local preference” selection rule will
prefer the customer route (through the backup link) to the peer route (through the primary link).

# 4

No it does not. It is somewhat troublesome due to the peer-peer agreement between Z, Y, X. Since Z wants to transit Y's traffic, Z will send route advertisements to Y.

In this manner, when Y has a datagram that is destined to an IP that can be reached through Z, Y will have the option of sending the datagram through Z. However, if Z advertises routes to Y, Y can re-advertise those routes to X.

Therefore, in this case, there is nothing Z can do from preventing traffic from X to transit through Z.