PHComparison chart
TCP UDP
Acronym for
Transmission Control Protocol
User Datagram Protocol or Universal Datagram Protocol
Connection
TCP is a connection-oriented protocol.
UDP is a connectionless protocol.
Function
As a message makes its way across the internet from one computer to another. This is connection based.
UDP is also a protocol used in message transport or transfer. This is not connection based which means that one program can send a load of packets to another and that would be the end of the relationship.
Usage
TCP is suited for applications that require high reliability, and transmission time is relatively less critical.
UDP is suitable for applications that need fast, efficient transmission, such as games. UDP's stateless nature is also useful for servers that answer small queries from huge numbers of clients.
Use by other protocols
HTTP, HTTPs, FTP, SMTP, Telnet
DNS, DHCP, TFTP, SNMP, RIP, VOIP.
Ordering of data packets
TCP rearranges data packets in the order specified.
UDP has no inherent order as all packets are independent of each other. If ordering is required, it has to be managed by the application layer.
Speed of transfer
The speed for TCP is slower than UDP.
UDP is faster because error recovery is not attempted. It is a "best effort" protocol.
Reliability
There is absolute guarantee that the data transferred remains intact and arrives in the same order in which it was sent.
There is no guarantee that the messages or packets sent would reach at all.
Header Size
TCP header size is 20 bytes
UDP Header size is 8 bytes.
Common Header Fields
Source port, Destination port, Check Sum
Source port, Destination port, Check Sum
Streaming of data
Data is read as a byte stream, no distinguishing indications are transmitted to signal message (segment) boundaries.
Packets are sent individually and are checked for integrity only if they arrive. Packets have definite boundaries which are honored upon receipt, meaning a read operation at the receiver socket will yield an entire message as it was originally sent.
Weight
TCP is heavy-weight. TCP requires three packets to set up a socket connection, before any user data can be sent. TCP handles reliability and congestion control.
UDP is lightweight. There is no ordering of messages, no tracking connections, etc. It is a small transport layer designed on top of IP.
Data Flow Control
TCP does Flow Control. TCP requires three packets to set up a socket connection, before any user data can be sent. TCP handles reliability and congestion control.
UDP does not have an option for flow control
Error Checking
TCP does error checking and error recovery. Erroneous packets are retransmitted from the source to the destination.
UDP does error checking but simply discards erroneous packets. Error recovery is not attempted.
Fields
1. Sequence Number, 2. AcK number, 3. Data offset, 4. Reserved, 5. Control bit, 6. Window, 7. Urgent Pointer 8. Options, 9. Padding, 10. Check Sum, 11. Source port, 12. Destination port
1. Length, 2. Source port, 3. Destination port, 4. Check Sum
Acknowledgement
Acknowledgement segments
No Acknowledgment
Handshake
SYN, SYN-ACK, ACK
No handshake (connectionless protocol)
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TCP UDP
Acronym for
Transmission Control Protocol
User Datagram Protocol or Universal Datagram Protocol
Connection
TCP is a connection-oriented protocol.
UDP is a connectionless protocol.
Function
As a message makes its way across the internet from one computer to another. This is connection based.
UDP is also a protocol used in message transport or transfer. This is not connection based which means that one program can send a load of packets to another and that would be the end of the relationship.
Usage
TCP is suited for applications that require high reliability, and transmission time is relatively less critical.
UDP is suitable for applications that need fast, efficient transmission, such as games. UDP's stateless nature is also useful for servers that answer small queries from huge numbers of clients.
Use by other protocols
HTTP, HTTPs, FTP, SMTP, Telnet
DNS, DHCP, TFTP, SNMP, RIP, VOIP.
Ordering of data packets
TCP rearranges data packets in the order specified.
UDP has no inherent order as all packets are independent of each other. If ordering is required, it has to be managed by the application layer.
Speed of transfer
The speed for TCP is slower than UDP.
UDP is faster because error recovery is not attempted. It is a "best effort" protocol.
Reliability
There is absolute guarantee that the data transferred remains intact and arrives in the same order in which it was sent.
There is no guarantee that the messages or packets sent would reach at all.
Header Size
TCP header size is 20 bytes
UDP Header size is 8 bytes.
Common Header Fields
Source port, Destination port, Check Sum
Source port, Destination port, Check Sum
Streaming of data
Data is read as a byte stream, no distinguishing indications are transmitted to signal message (segment) boundaries.
Packets are sent individually and are checked for integrity only if they arrive. Packets have definite boundaries which are honored upon receipt, meaning a read operation at the receiver socket will yield an entire message as it was originally sent.
Weight
TCP is heavy-weight. TCP requires three packets to set up a socket connection, before any user data can be sent. TCP handles reliability and congestion control.
UDP is lightweight. There is no ordering of messages, no tracking connections, etc. It is a small transport layer designed on top of IP.
Data Flow Control
TCP does Flow Control. TCP requires three packets to set up a socket connection, before any user data can be sent. TCP handles reliability and congestion control.
UDP does not have an option for flow control
Error Checking
TCP does error checking and error recovery. Erroneous packets are retransmitted from the source to the destination.
UDP does error checking but simply discards erroneous packets. Error recovery is not attempted.
Fields
1. Sequence Number, 2. AcK number, 3. Data offset, 4. Reserved, 5. Control bit, 6. Window, 7. Urgent Pointer 8. Options, 9. Padding, 10. Check Sum, 11. Source port, 12. Destination port
1. Length, 2. Source port, 3. Destination port, 4. Check Sum
Acknowledgement
Acknowledgement segments
No Acknowledgment
Handshake
SYN, SYN-ACK, ACK
No handshake (connectionless protocol)
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