Transport Layer Protocols

Computer Networks:

Physical Layers

Data link Layer(DLL)

Network Layer

Transport Layer:

Session and Presentation Layer:

Application Layer:

Transport Layer

Transport Layer Protocol

1) Transmission control protocol TCP:

Transmission control protocol (TCP), provide a reliable connection oriented service. Connection oriented means both the client and server must open the connection before data is sent.

TCP provides are connection oriented reliable service.
TCP guarantees the delivery of the data pack, if the data is lost across the network then the TCP will reach and lost packet.
It provides a flow control mechanism using a slide window protocol.
It provides error control.

TCP Message format:

Source Port number 16 bit.
Destination port number 16 bit.
Sequence number (32 bit) this field contains the sequence number of data bit in a particular session.
Acknowledgements Number (32 bit): Contains the next sequence that the sender of the acknowledgement expect to received which is the sequence number +1. This number is used only if the acknowledgement flag is on.
Header length 4 bit: This length of the header is 32 bit word, required since the option field is variable in length.
Reserve (6 bit) it is used for future use.
FLAGS:
That are 6 control beat or flags;

URG : is a 1 bit makes the urgent pointer is valid.
ACK : is a 1 bit show acknowledgement (ACK) number valid.
PSH :1 bit higher priority data for the application.
RST :1 bit reset the connection.
SYN :1 bit Turned on when a connection Is being established and the sequence number field will content the initial sequence number chosen by the host for the connection.
FIN : is a 1 bit, show when the sender is done sending data.

Windows size 16 bit the maximum number of bytes that the receiver will to accept.
TCP checksum 16 bit over the TCP header, data, and TCP pseudo header.

Urgent pointer 16 bit it is only valid if the URG bit is set, the urgent mode is a way to transmit emergency data to the other side of the connection

Option (variable length) the header is followed by data TCP data is full duplex.

2) User Datagram protocol (UDP):

UDP is a transport layer protocol user datagram protocol is a part of Internet Protocol suit. UDP is an unreliable and connectionless protocol. So there is no need to established a connection prior to data transfer .
There is no guarantee that the data will reach its destination.it means to provide services with very little transmission overhead. it adds very little to IP data packet accept for some error checking and port direction.

Benefit of user datagram protocol

No retransmission delay: UDP is suitable for time sensitive application that can’t afford Re transmission delay for dropping package example online gaming.
Speed UTP speed makes its useful for query response packet such as DNS.
Suitable for broadcasting UDP is lack of end to end connection make it suitable for broadcast

Downside of UDP :

No guarantee of packet received.
No protection against duplicate packets.
The UDP message can be lost, delay, duplicate or can be out of order

UDP Header Format:

Source code number;
It is 16 bit information that identify which Port is going to send the packet.
Destination port number: destination port number identify which port is going to accept the information it is 16 bit long.

Length is 16 bit field that specify the entire length of the UDP packet that includes the header also.

Checksum it is 16 bit field and it is optional feed this check some field checks whether the information is accurate or not.

Difference Between TCP and UDP

The Transport Layer Protocol are TCP and UDP

TCP	UDP
TCP stands for transmission control protocol.	UDP stands for user datagram protocol.
TCP is a connection oriented protocol, which means connection needs to be established before the data is transmission.	UDP is a connectionless protocol which means that the data can be directly send without established connection before.
TCP is a reliable protocol as it assure for the delivery of the data.	UDP is unreliable protocol.
TCP is slower than you UDP	UTP is faster than TCP
The size of TCP is 20 beat byte	The size of the header is 8 by
TCP uses handshake technique such as SYN, ACK, SYN-ACK	UDP does not use handshake.
TCP does not support broadcasting	UDP support Broadcasting
Some protocols used by TCP are HTTP,HTTPs,FTP, SMTP, tellnet	Some protocol used by UDP is DNS, DHCP, TFTP,RIP,VoIP