Connection Management | Computer Networks - Computer Science Engineering (CSE) PDF Download

Connection Managment
A TCP connection begins with a client doing an active open to a server. Assuming that the server had earlier done a passive open, the two sides engage in an exchange of messages to establish the connection. Only after this connection establishment phase is over do the two sides begin sending data. Likewise, as soon as a participant is done sending data, it closes one direction of the connection, which causes TCP to initiate a round of connection termination messages.

Connection setup is an asymmetric activity (one side does a passive open and the other side does an active open) connection teardown is symmetric (each side has to close the  connection independently). Therefore it is possible for one side to have done a close, meaning that it can no longer send data but for the other side to keep the other half of the bidirectional connection opens and to continue sending data.

Three Way Handshakes:
The algorithm used by TCP to establish and terminate a connection is called a three way handshake.  The    client (the    active participant) sends a segment to the server(the passive participation) stating the initial sequence number it plans to use(flag =SYN,SequenceNum =x).

The server then responds with a single segment that both acknowledges the client‟s sequence  number  (Flags  =ACK,  Ack=x+1)  and  states  its  own  beginning  sequence  number
(Flags=SYN, SequenceNum=y).
Connection Management | Computer Networks - Computer Science Engineering (CSE)

 

That is, both the SYN and ACK bits are set in the Flags field of this second message. Finally, the client responds with a third segment that acknowledges the server‟s sequence number Flags =ACK, Ack=y+1).

The "three-way handshake" is the procedure used to establish a connection. This procedure normally is initiated by one TCP and responded to by another TCP. The procedure also works if two TCP simultaneously initiate the procedure. When simultaneous attempt occurs, each TCP receives a "SYN" segment which carries no acknowledgment after it has sent a "SYN". Of course, the arrival of an old duplicate "SYN" segment can potentially make it appear, to the recipient, that a simultaneous connection initiation is in progress. Proper use of "reset" segments can disambiguate these cases.

The three-way handshake reduces the possibility of false connections. It is the implementation of a trade-off between memory and messages to provide information for this checking.

The simplest three-way handshake is shown in figure below. The figures should be interpreted in the following way. Each line is numbered for reference purposes. Right arrows (-->) indicate departure of a TCP segment from TCP A to TCP B, or arrival of a segment at B from A. Left arrows (<--), indicate the reverse. Ellipsis (...) indicates a segment which is still in the network (delayed). TCP states represent the state AFTER the departure or arrival of the segment (whose contents are shown in the center of each line). Segment contents are shown in abbreviated form, with sequence number, control flags, and ACK field. Other fields such as window, addresses, lengths, and text have been left out in the interest of clarity.


      Connection Management | Computer Networks - Computer Science Engineering (CSE)

\ Connection Management | Computer Networks - Computer Science Engineering (CSE)
Basic 3-Way Handshake for Connection Synchronisation

In line 2 of above figure, TCP A begins by sending a SYN segment indicating that it will use sequence numbers starting with sequence number 100. In line 3, TCP B sends a SYN and acknowledges the SYN it received from TCP A. Note that the acknowledgment field indicates TCP B is now expecting to hear sequence 101, acknowledging the SYN which occupied sequence 100.

At line 4, TCP A responds with an empty segment containing an ACK for TCP B's SYN; and in line 5, TCP A sends some data. Note that the sequence number of the segment in line 5 is the same as in line 4 because the ACK does not occupy sequence number space (if it did, we would wind up ACKing ACK's!).
Connection Management | Computer Networks - Computer Science Engineering (CSE)

The document Connection Management | Computer Networks - Computer Science Engineering (CSE) is a part of the Computer Science Engineering (CSE) Course Computer Networks.
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FAQs on Connection Management - Computer Networks - Computer Science Engineering (CSE)

1. What is connection management in networking?
Ans. Connection management refers to the process of establishing, maintaining, and terminating connections between devices or systems in a network. It involves various protocols and techniques to ensure reliable and efficient communication between network entities.
2. Why is connection management important in networking?
Ans. Connection management is crucial in networking as it ensures the smooth flow of data between devices or systems. It allows for efficient resource allocation, error detection, and recovery. By managing connections, network performance and reliability can be optimized.
3. What are the common connection management protocols used in networking?
Ans. Some commonly used connection management protocols in networking include Transmission Control Protocol (TCP), User Datagram Protocol (UDP), and Internet Control Message Protocol (ICMP). These protocols provide mechanisms for establishing, maintaining, and terminating connections.
4. How does connection management help in preventing congestion in networks?
Ans. Connection management plays a vital role in preventing congestion in networks. It incorporates flow control mechanisms to regulate the rate of data transmission, ensuring that the network does not become overloaded. By controlling the flow of data, connection management helps in maintaining network stability and preventing congestion.
5. What are the challenges in connection management for large-scale networks?
Ans. Large-scale networks pose several challenges for connection management. Some of these challenges include scalability, security, and fault tolerance. Managing a vast number of connections efficiently, ensuring data privacy and integrity, and handling failures or disruptions in a large-scale network are key concerns that need to be addressed.
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