User Data News Agreement (UDP) Introduction
The user datagram protocol is a protocol that defines a computer communication that is used to exchange in a interconnected network environment. This protocol defaults that the Internet Protocol (IP) is its underlying protocol. This agreement provides the easiest protocol mechanism to send information to another user program. This protocol is operational, not submitted and replicated. If the application requires reliable data transfer, the Transmission Control Protocol (TCP) should be used. Data report formats are as follows:
0 7 8 15 16 23 24 31 ----------- -------- ------------------ ---------------- ------ ------ | Source port | destination port | -------------------- ------------ | Length | Check code | ---------- ----- ----- ------------ | Data ... --------- -------- .......
User Data Date
User data header format
area
The source port is an optional domain. When it makes sense, it refers to the port of the transmission process, which is assumed to return information to the message without other information. If it is not used, it is filled in this domain. The destination port is meaningful when there is a specific destination network address. The length refers to an octal representation of this user data report length. (This indicates that the smallest data report length is 8.) The check code has 16 bits, which is to reflect on and re-reflect on the number of IP headers, UDP headers, and data.
The header is conceptually, before the UDP header information, it includes an active address, destination address, protocol and UDP length used. These information make information cannot be received incorrectly. This verification process is consistent with the process used in TCP.
0 7 8 15 16 23 24 31 ----------- -------- ------------------ ---------------- ------ ------ | Source address | ----------- --------- -------- --- --------- | Destination address | ----------- --------- ---------- ------------ | 0 | Agreement | UDP length | ---- ---- ---- ------ ---- - ----- ---- ------
If the calculated check code is zero, it will be sent alloy. The full check value means that the sender does not produce a check code.
User interface
The user interface should allow the new receiving port to receive the receiving operation: You should return an octal number of description source ports and source addresses, allowing datagrams to send, specify data, source, and destination ports, and destination address.
IP layer interface
The UDP module must be able to determine the network address of the source and the target, and must be able to know the protocol used from the header. One possible interface mode is to return the entire datagram, including the header returned by the receiving operation. Such an interface should also allow UDP to transmit a full-headed data report for the IP to transmit. The consistency is determined by IP and the check code is calculated.
Protocol application
The main use of this agreement is the Internet Name Server and Small File Transfer Protocol (TFTP). Protocol number
When using it in IP, its protocol number is 17 (an octatifice is 21). ?
