Week 12 - Routing + Transport Layer

Question 1

What type of routing are we focusing on in this course?

Answer 1

Unicast (1 to 1)

Question 2

How are routing protocols and forwarding tables related?

Answer 2

Routing protocols are correlated to a routing table. The forwarding tables contain the best routes for packet forwarding based on the routing table.

Question 3

What is a Link-State Routing Algorithm?

Answer 3

Centralized - all routers have knowledge of the entire network (LSDB)

Each node’s LSP has info about immediate neighbours

Nodes flood entire network with link-state packets (LSPs) so that each router knows the topology.

Then utilizes LSPs and Djikstra’s to find least cost path from a node.

Question 4

What is a Distance-Vector Routing Algorithm?

Answer 4

Decentralized routing algo

1D array contains least costs to all other nodes, not the paths.

Nodes send vector to neighbours, neighbours update own vectors with Bellman-Ford equation.

Question 5

What needs a forwarding table?

Answer 5

Only the routers.

Question 6

What is an autonomous system (AS)?

Answer 6

In hierarchical routing, each ISP is an AS. Each AS runs its own routing protocol.

Question 7

What is the difference between Intra-AS and Inter-AS routing protocols?

Answer 7

Intra-AS: routing protocol run in each AS

Inter-AS: the global routing protocol that glues the ASs together (think international)

Question 8

What are the two common intradomain routing protocols?

Answer 8

RIP and OSPF

Question 9

What is the interdomain routing protocol?

Answer 9

BGP

Question 10

What is the Routing Information Protocol (RIP)?

Answer 10

Based on distance vector routing algo.

Routers advertise cost of reaching different networks based on hops.

A hop is the number of subnets a packet needs to travel through

Question 11

What is Open Shortest Path First (OSPF)?

Answer 11

Based on link-state routing algorithm

Each link/subnet is assigned weight

Finds “shortest” path from source to dest node.

Question 12

What is an OSPF area?

Answer 12

A section of the AS, creates a domain for flooding LSPs.

Area border routers required.

Question 13

What are the 5 transport layer services?

Answer 13

Process-to-process comm
Addressing: Port #s
Encap/decap
Flow control
Error control

Question 14

What do port numbers provide?

Answer 14

End-to-end addresses at the transport layer

Question 15

What is the main paradigm for process-to-process communication?

Answer 15

Client/server

Question 16

What is a socket address?

Answer 16

A combination of an IP address and a port number

Uniquely identifies client or server process

Question 17

How is transport layer flow control performed?

Answer 17

Sender and receiver hold buffers, receiver communicates with sender.

Question 18

How is transport layer error control performed?

Answer 18

By using sequence numbers and acknowledgements.

handles packets that are corrupted, duplicated, lost, or out of order.

Unlike network layer error control which drops packets. Can resend and reorder packets.

Question 19

Is UDP simplex, half-duplex, or full-duplex

Answer 19

half-duplex