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MTU fragmentation in network transmission: How to avoid data loss and retransmission?
In modern computer networks, the Maximum Transmission Unit (MTU) plays a vital role. MTU refers to the size of the largest protocol data unit that can be transmitted in a network layer transaction. MTU is related to, but not identical to, the maximum frame size of a data link layer such as Ethernet. Proper MTU settings can not only improve data transmission efficiency, but also help reduce the number of retransmissions and data loss.
Proper configuration of the MTU can significantly impact network performance, especially in large data transfer scenarios.
The size of the MTU depends on the capabilities of the underlying network and usually requires manual or automatic adjustment so as not to exceed those capabilities. For example, taking Ethernet, its maximum frame size is 1518 bytes, of which 18 bytes are overhead, resulting in an MTU of 1500 bytes. Such fixed standards allow the legality of the structure to be maintained when transmitting over different networks.
Impact of MTU
Choosing a larger MTU improves the efficiency of data transmission because each network packet carries a larger amount of effective data, while the protocol overhead remains fixed. However, a larger MTU also introduces some problems, such as potentially longer transmission delays, especially for subsequent packets. Such delays, if not managed, can have an impact on the entire network environment.
In some cases, the transmission of large data packets may result in higher packet loss rates. If a single byte is corrupted, the entire data packet will be retransmitted, which will waste valuable bandwidth.
In addition, large packet transmission is particularly undesirable in the presence of communication errors. If the system used is unable to perform forward error correction, the corruption of one byte can cause the entire packet to be discarded, which is especially common in network environments with high packet loss rates.
The relationship between Internet protocols and MTU
The Internet Protocol (IP) was designed to run on a number of different network technologies, which may support different sized packets. While a host is aware of its own MTU and the MTU of potential peers, it does not immediately know what the minimum MTU is along the links to other peers. This creates potential problems, especially when higher-level protocols create packet sizes larger than the local link can support.
The IP protocol allows packet fragmentation, dividing a datagram into several smaller parts to fit within the limitations of a specific MTU.
This fragmentation process occurs at the Internet level, and fragmented packets are marked so that the IP layer of the destination host knows to reassemble them back into the original datagram. However, if the network loses any segment, the entire packet is considered lost. In this case, unreasonable or unnecessary overhead will result when the number of packets or their contents that need to be fragmented is too large.
MTU discovery and configuration
MTU discovery technology is used to discover the minimum MTU of any Internet transmission path. By sending a packet with the no-fragmentation option to a device in the path, if the device's MTU is smaller than the packet, the packet will be dropped and an ICMP description message will be returned. This process is repeated until a small enough MTU is found.
But as more and more networks block ICMP traffic, the capabilities of MTU discovery technology are limited, which can lead to unexpected obstacles in the way the network handles data transfers.
One way to solve this problem is to adjust the maximum segment size (MSS) in the TCP connection to maximize the efficiency of transmitting data. This will be very important to improve the smoothness of data transmission in non-standard network environments.
Conclusion
As network technology continues to evolve, MTU setting and management become more and more complex. How to effectively configure and optimize MTU to improve the stability and efficiency of data transmission has become a question worth pondering?
