Connection establishment involves a handshake process between two endpoints to synchronize sequence numbers and establish communication. Transport protocols like TCP require a connection to be set up before data can be exchanged. This allows each end to verify the other's existence, negotiate parameters, and allocate resources. Common connection establishment methods are two-way and three-way handshakes, with three-way involving SYN, SYN-ACK and ACK packets. Flow control mechanisms like stop-and-wait and sliding windows ensure transmission rates match receiver capabilities to prevent buffer overruns. Congestion control is also important to manage network traffic loads and avoid degrading performance due to delays or reduced throughput when congestion occurs.

2. Connection Establishment
⚫A connection is a requirementof a reliabledata
delivery service.
⚫It is set up before theactual dataexchange takes place.
⚫ The connection is used toacknowledge the receiptof
packets and retransmit those thatare lost.

3. Requirement
⚫Required byconnection-oriented transport protocols
like TCP
⚫Need connection establishment procedures toallow:
each end to know theotherexists
negotiation of optional parameters
triggers allocationof transportentity resources

4. Ways of Establish the connection
⚫Two-Way Handshake
⚫Three-Way Handshake

5. Three-Way Handshake
SYN+ACK

6. ⚫SYN:
⚫It is forsynchronization of sequence numbers
⚫It consumes 1 sequence number
⚫Carries no real data
⚫SYN+ACK:
⚫SYN segment forcommunication in otherdirection and
⚫ACK forthe received SYN
⚫It consumes 1 sequence number
⚫ACK
⚫Justan ACK segment
⚫Does not consume any sequence number

7. ⚫threeway handshake
SYN, SYN-ACK, ACK
⚫connection determined by sourceand destination
sockets (host, port)
⚫can only havea single connection between any unique
pairsof ports
⚫butone portcan connect to multipleports

8. Flow Control
⚫Flowcontrol is the mechanism thatensures the rateat
which a sender is transmitting is in proportion with
the receiver’s receiving capabilities.

9. Flow Control Method
⚫Stop-and-wait
⚫Sliding-window

10. Stop-and-wait
⚫This is the simplest form of flow control where a sender
transmits a data frame. After receiving the frame, the
receiver indicates its willingness to accept another frame
by sending back an ACK frame acknowledging the frame
just received.

11. Sliding-window
⚫With the useof multiple frames fora single message,
the stop-and-wait protocol does not perform well.
Only one frame at a time can be in transit. In stop-
and-wait flow control, if a > 1, serious inefficiencies
result.

12. ⚫Sendersliding Window:
⚫Receiversliding Window:

13. Congestion Control
⚫Congestion isa situation in Communication Networks
in which too many packets are present in a part of the
subnet, performance degrades. Congestion in a
network mayoccurwhen the load on the
network (i.e. the numberof packets sent to the
network) is greater than the capacity of the
network (i.e. the numberof packetsa network can
handle.). Networkcongestionoccurs in caseof traffic
overloading.

14. Causes Of Congestion
⚫if all of a sudden a stream of packets arrive on several
input linesand need to beouton the sameoutput line.
⚫Slowprocessorsalsocause Congestion. If the router
CPU is slowat performing the task.

15. Effects of Congestion
⚫Congestion affects twovital parameters of the network
performance
⚫1. Through put
⚫2. Delay

16. Congestion Control Techniques
⚫Open loop: Protocols topreventoravoid congestion,
ensuring that the system never enters a Congested
State.
⚫Close loop: Protocols thatallowsystem toenter
congested state, detect it, and remove it.

17. Congestion Control Algorithms
⚫Leaky BucketAlgorithm
⚫Token BucketAlgorithm