Data Communications Principles Assignment 2

CP5601 - 2018 SP53 JCUS
Data Communications Principles
Assignment 2
Submit your answers as a Word document to Assessment Task 3 in LearnJCU.
Question 1 Suppose the following network uses datagram routing and all links have the
same bit rate.
 Find the routing table for each node, using minimum hop routing.
Routing for Node A: Routing for NodeB:
Destination
Node Next
Node
B B
C C
D B
E B
F B
Routing for Node C: Routing for Node D:
Destination
Node Next
Node
A A
B A
D D
E D
F D
Routing for Node E: Routing for Node F:
Destination
Node Next
Node
A A
C D
D D
E D
F D
Destination
Node Next
Node
A B
B B
C C
E E
F F
Destination
Node Next
Node
A D
B D
C D
D D
F D
Destination
Node Next Node
A D
B D
C D
D D
E D

CP5601 - 2018 SP53 JCUS
 Reconstruct the routing table for each node if node B fails.
Routing for Node A: Routing for NodeB:
Destination
Node Next
Node
B -
C C
D C
E C
F C
Routing for Node C: Routing for Node D:
Destination
Node Next
Node
A A
B -
D D
E D
F D
Routing for Node E: Routing for Node F:
Destination
Node Next
Node
A D
B D
C D
D D
F D
Destination
Node Next
Node
- -
- -
- -
- -
- -
Destination
Node Next
Node
A C
B -
C C
E E
F F
Destination
Node Next
Node
A D
B D
C D
D D
E D

CP5601 - 2018 SP53 JCUS
Question 2
Explain in detail how a TCP connection is established and closed.
 What is TCP flow control and how it works?
You may use diagrams and examples in answers.
To build up an association, TCP utilizes a three-way handshake. Before a client can
associate with a server, the server should initially setup a channel at a port to open it up
for associations. When the connection is set up, a client may start a data exchange. To set
up an association, the three-way (or 3-step) handshake happens:
SYN: The first step is to request an open port. This is done by sending a SYN packet to
the server.
SYN-ACK: In response, the server responds with a SYN-ACK packet.
ACK: Finally, the client sends an ACK packet back to the server.
Once these three steps are complete, the channel between server and client is setup to
exchange data by method of data packets. Each packet contains a packet sequence number
to track the data integrity and manage data flow control.
TCP uses a sliding window protocol to keep track of packets being transmitted. This
protocol requires packets to be acknowledged before new packets can be transmitted. The
number of packets held for transmission are defined by the window size of the receiver
and sender involved. Flow control mechanism is implemented using several techniques
that manipulate the window size of the sender. The window size of the sender is
dependent upon number of packets ACK by the receiver. The reduced number of packets
being acknowledged reduces packets being transmitted by the sender, and increased
number of packets allows sender to increase flow of data. This way TCP manages the
flow control on a network along with several other mechanisms like delay re-transmission
and selective repeat of lost packets to reduce network traffic while maintaining connection
quality and reliability.