TCP vs UDP Connections
| Item | TCP | UDP |
|---|---|---|
| Acronym for | Transmission Control Protocol | User Datagram Protocol or Universal Datagram 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 used in case of non-time critical applications. | UDP is used for games or applications that require fast transmission of data. UDP's stateless nature is also useful for servers that answer small queries from huge numbers of clients. |
| Examples: | HTTP, HTTPs, FTP, SMTP Telnet etc... | DNS, DHCP, TFTP, SNMP, RIP, VOIP etc... |
| 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 there is no error-checking for packets. |
| 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. |
| 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 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 | UDP does error checking, but no recovery options. |
| 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 |
