Cn notes

1. SRI KRISHNA GROUP OF
INSTITUTION
SUBJECT : COMPUTER NETWORKS.
SUBCODE : 21CS52
TOPIC : CONNECTION ESTABLISHMENT (MOD-4)
UNDER THE GUIDANCE OF : PRADEEPA MAM (Ast Prof of ISE)
DONE BY: CHANDANA L (1KT21IS008) ISE

2. Formal Introduction
• Establishing a connection sounds easy, but it is actually surprisingly
tricky.
• At first glance, it would seem sufficient for one transport entity to just
send a CONNECTION REQUEST segment to the destination and wait for a
CONNECTION ACCEPTED reply.
• The major problem occurs when the network can lose, delay, corrupt,
and duplicate packets.

3. • Consider the network using datagrams inside and every packet
follows a different route. Some of the packets might get stuck in
a traffic jam inside the network and take a long time to arrive.
• This scheme has a basic flaw: it requires each transport entity to
maintain a certain amount of history information indefinitely.
This history must have both the source and destination
machines. Otherwise, if a machine crashes and loses its
memory.

4. • Packet lifetime can be restricted of the following techniques:
1. Restricted network design.
2. Putting a hop counter in each packet.
3. Timestamping each packet.
• The first technique includes - method that prevents packets from
looping, combined with bounding delay.
• The Second Technique includes- hop count initialized to some value
and decremented each time the packet is forwarded.
• The Third method requires each packet to bear the time it was
created, with the routers agreeing to discard any packet older than
some agreed-upon time.

5. • The connection establishment in
TCP is called three-way hand
shaking.
• Here the client makes
connection with another
application prog called
“SERVER”.
• This req is called passive open.
• TCP now starts 3-way
handshaking process.
• The client takes a random
number called Initial
Sequence(ISN)
3- Way Handshaking

6. • SYN segment is a control
segment and carries no data.
• Now the server sends the
second segment called SYN+ACK
segment with two flag bits set.
• SYN segment is for
communication, sequence num
is 13000.
• ACK flag has sequence num of
6001 which the sever expects to
receive frm the client.
• At last the client sends the third
segment that is ACK segment.
• It acknowledges the second
segment with ACK flag and
acknowledgement number
13001.
• Same sequence num as SYN
segment I,e 6000; ACK segment
does not consume any sequence
number.
• NOTE- Third segment does not
carry data and consumes no
sequence numbers.

7. THANK YOU !!