Telecom & Comp Ntwkg 3

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Assignment#3

MMIS 653 (Winter 2013)

Total points: 60

Due date: 3/19/2013 11:59PM

1, What is the difference between routing and forwarding? (4 points)

2, What is HOL blocking? Does it occur in input ports or output ports? (4 points)

3, Do routers have IP addresses? If so, how many? How many IP addresses does a

computer have? (4 points)

4, Is it necessary that every autonomous system use the same Intra-AS routing algorithm?

Why or why not? (4 points)

5, Consider the following network topology:

Assume the original routing table in D is as below.

Now suppose that D receives from A the following advertisement:

Will the table in D change? If so how? (5 points)

6, Define and contrast the following terms: subnet, prefix, and BGP route? (4 points)

7, Consider a virtual-circuit network. Suppose the VC number is a 4-bit field. (4 points)

a, What is the maximum number of virtual circuits that can be carried over a link?

b, Suppose that different VC numbers are permitted in each link along a VC’s path.

During connection setup, after an end-to-end path is determined, describe how the links

can choose their VC numbers and configure their forwarding tables in a decentralized

manner, without reliance on a central node.

8, Consider a datagram network using 16-bit host addresses. Suppose a router uses

longest prefix matching and has the following forwarding table:

———————————————–

Prefix Match Interface

———————————————–

1 0
11 1
111 2
Otherwise 3

———————————————–

For each of the four interfaces, give the associated range of destination host addresses

and the number of addresses in the range. (8 points)

9, Consider sending a 4000-byte datagram into a link that has an MTU of 500 bytes.

Suppose the original datagram is stamped with the identification number 526. How many

fragments are generated? What are their characteristics? (Assume IPv4 is used so the IP

header is 20 bytes in length) (8 points)

10, Consider the following network. With the indicated link costs, use Dijkstra’s shortest-

path algorithm to compute the shortest path from z to all network nodes. Show how the

algorithm works by computing a table similar to Table 4.3 on page 379. (15 points)