This link has been bookmarked by 39 people . It was first bookmarked on 02 Mar 2006, by techieme Ron.
-
07 May 15
-
TCP also implements a congestion-control mechanism.
-
TCP includes a flow-control mechanism for each of these byte streams that allows the receiver to limit how much data the sender can transmit.
-
The congestion window is flow control imposed by the sender, while the advertised window is flow control imposed by the receiver.
-
The former is based on the sender's assessment of perceived network congestion; the latter is related to the amount of available buffer space at the receiver for this connection.
-
Fast Retransmit
TCP may generate an immediate acknowledgment (a duplicate ACK) when an out- of-order segment is received. This duplicate ACK should not be delayed.
-
The purpose of this duplicate ACK is to let the other end know that a segment was received out of order, and to tell it what sequence number is expected.
-
Since TCP does not know whether a duplicate ACK is caused by a lost segment or just a reordering of segments, it waits for a small number of duplicate ACKs to be received. It is assumed that if there is just a reordering of the segments, there will be only one or two duplicate ACKs before the reordered segment is processed, which will then generate a new ACK. If three or more duplicate ACKs are received in a row, it is a strong indication that a segment has been lost. TCP then performs a retransmission of what appears to be the missing segment, without waiting for a retransmission timer to expire.
-
-
14 Aug 14
-
28 Nov 13
-
The Acknowledgement, SequenceNum, and AdvertisedWindow fields are all involved in TCP's sliding window algorithm.The Acknowledgement and AdvertisedW indow fields carry information about the flow of dat going in the other direction. In TCP's sliding window algorithm the reciever advertises a window size to the sender. This is done using the AdvertisedWindow field. The sender is then limited to having no more than a value of AdvertisedWindow bytes of un acknowledged data at any given time. The receiver sets a suitable value for the AdvertisedWindow based on the amount of memory allocated to the connection for the purpose of buffering data.
-
-
16 Aug 13
-
12 Feb 13
Osamu MATSUMOTO"ssthre"
-
19 Apr 12
-
12 May 11
-
low start adds another window to the sender's TCP: the congestion window, called "cwnd". When a new connection is established with a host on another network, the congestion window is initialized to one segment (i.e., the segment size announced by the other end, or the default, typically 536 or 512). Each time an ACK is received, the congestion window is increased by one segment. The sender can transmit up to the minimum of the congestion window and the advertised window. The congestion window is flow control imposed by the sender, while the advertised window is flow control imposed by the receiver. The former is based on the sender's assessment of perceived network congestion; the latter is related to the amount of available buffer space at the receiver for this connection.
The sender starts by transmitting one segment and waiting for its ACK. When that ACK is received, the congestion window is incremented from one to two, and two segments can be sent. When each of those two segments is acknowledged, the congestion window is increased to four. This provides an exponential growth, although it is not exactly exponential because the receiver may delay its ACKs, typically sending one ACK for every two segments that it receives.
At some point the capacity of the internet can be reached, and an intermediate router will start discarding packets. This tells the sender that its congestion window has gotten too large.
-
-
21 Feb 11
-
When a new connection is established with a host on another network, the congestion window is initialized to one segment (i.e., the segment size announced by the other end, or the default, typically 536 or 512). Each time an ACK is received, the congestion window is increased by one segment. The sender can transmit up to the minimum of the congestion window and the advertised window.
-
-
31 Dec 10
-
15 Mar 10
-
28 Oct 09
-
17 Apr 09
-
09 Dec 08
-
22 Aug 08
-
28 Jul 08
-
28 Apr 08
-
20 Jun 06
-
13 Nov 05
Would you like to comment?
Join Diigo for a free account, or sign in if you are already a member.