TCP vs UDP

Definition

There are two types of Internet Protocol (IP) traffic. They are TCP or Transmission Control Protocol and UDP or User Datagram Protocol.

TCP is connection-oriented – once a connection is established, data can be sent bidirectional.

UDP is a simpler, connectionless Internet protocol. Multiple messages are sent as packets in chunks using UDP.

Common pros and cons

Criteria

TCP

UDP

better

  • Reliability

  • Data Flow Control

  • Ordering

  • Error Checking

  • Speed

  • Header size is less

  • Weight

worse

  • Speed

  • Header Size is bigger

  • Weight

  • Reliability

  • Data Flow Control

  • Ordering

  • Error Checking

General information

Criteria

TCP

UDP

Acronym for

Transmission Control Protocol

User Datagram Protocol or Universal Datagram Protocol

Connection

Transmission Control Protocol is a connection-oriented protocol.

User Datagram Protocol 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. CheckSum

11. Source port

12. Destination port

1. Length

2. Source port

3. Destination port

4. CheckSum

Acknowledgment

Acknowledgment segments

No Acknowledgment

Handshake

SYN, SYN-ACK, ACK

No handshake (connectionless protocol)

Usage

Web browsing, email, and file transfer are common applications that make use of TCP. TCP is used to control segment size, rate of data exchange, flow control, and network congestion. TCP is preferred where error correction facilities are required at the network interface level.

UDP is largely used by time-sensitive applications as well as by servers that answer small queries from huge number of clients. UDP is compatible with packet broadcast - sending to all on a network and multicasting – sending to all subscribers. UDP is commonly used in Domain Name System, Voice over IP, Trivial File Transfer Protocol, and online games.

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