流量控制和 TCP 中的拥塞控制有什么区别？

TCP 中的流量控制和拥塞控制控制有什么区别？

这个问题可以分为两部分:

  1. 流量和拥塞控制的总体目的是什么？
  2. 这项任务是如何完成的？

根据 维基百科，TCP 流控制依赖于在 ACK 消息中报告的窗口大小。拥塞控制也依赖于确认消息。我想知道这两个目标之间的区别，以及它们是如何运作的。

102090 次浏览
小开
最佳答案

As to part 1, super general overview:

Flow control is controlled by the receiving side. It ensures that the sender only sends what the receiver can handle. Think of a situation where someone with a fast fiber connection might be sending to someone on dialup or something similar. The sender would have the ability to send packets very quickly, but that would be useless to the receiver on dialup, so they would need a way to throttle what the sending side can send. Flow control deals with the mechanisms available to ensure that this communication goes smoothly.

Congestion control is a method of ensuring that everyone across a network has a "fair" amount of access to network resources, at any given time. In a mixed-network environment, everyone needs to be able to assume the same general level of performance. A common scenario to help understand this is an office LAN. You have a number of LAN segments in an office all doing their thing within the LAN, but then they may all need to go out over a WAN link that is slower than the constituent LAN segments. Picture having 100mb connections within the LAN that ultimately go out through a 5mb WAN link. Some kind of congestion control would need to be in place there to ensure there are no issues across the greater network.

As to part 2:

If this is an interview-prep question, as you said above, I would consider taking some time to read up on TCP/IP in general. Don't use Wikipedia. RTFM! This is VERY much worth your time. You could argue that this is the most important protocol holding up most of the modern internet.

Things to read about for Flow Control: stop and wait, sliding window, PAUSE frames.

Things to read about for Congestion Control: QoS (Quality-of-Service), retransmission policies, windowing policies.

Beyond that, you can search for any particular vendor implementations (Cisco, etc..)

小开

Flow Control: Sender will send enough data that can be accommodated at the receiver end.

Congestion Control: Sender will reduce the amount of sent packets to avoid overflowing the router's buffer(Queue).

小开

Congestion control is a global issue – involves every router and host within the subnet

Flow control, that is scoped from point to point, involves just sender and receiver.

小开

Flow Control:

  • It makes sure that the sender does not overload the receiver.
  • It's a local phenomenon, unlike congestion control.
  • It's generally initiated by the sender.

Congestion control:

  • It makes sure that the network is able to handle the load of packets.
  • It's a global phenomenon and affects every host connected with that network.
  • It's initiated by the router.
小开

Congestion control:In addition to preventing the router's buffer from overflowing it also deals with two other important factors

  • Fairness: Starvation shouldn't occur for any host connected to the network.Although the terminology is way more complex.
  • Efficiency: The links should be utilised to their maximum capacity such that it doesn't cause congestion.
小开

Flow control is mainly done on the receiver side, to adjust how much data the sender is injecting into the network; congestion control is mainly done on the sender side, trying to sense congestion on the network by the timing of ACK-packets, to adjust the volume of data sent to the corresponding situation.

小开

Flow Control is done at the receiver side. If the sender sends packets greater than the receiver's buffer size, overflow occurs at the receiver's buffer. To avoid this overflow at the receiver side, there is a windowing technique used at the sender side. Congestion control is done at the sender side. This is a global phenomenon. This happens at the router. Router's buffer overflows when many senders try to push more packets through the same link.

小开

Flow Control:

  1. When the sender buffer is full then we prevent the source from sending the data so that data should not be dropped.
  2. Receiver buffer is full in this case.
  3. It can be achieved easily by sliding window protocol.

Congestion Control

  1. When we start transmitting the data from source then it reaches the destination with the help of the network. Congestion control preventing the source so the data should not be dropped by the router in the network.

  2. This issue is related to the queue of the router

  3. It is more complicated to achieve because router gets different packets from the different source connected to its network.


提交答案