Operation
ECN requires specific support at the Internet and Transport layers for the following reasons:
- In TCP/IP routers operate mostly on the Internet layer while transmission rate is handled by the endpoints at the Transport layer
- Congestion may be handled only by the transmitter but since it is known to have happened only after a packet was sent, there must be an echo of the congestion indication by the receiver to the transmitter.
Without ECN congestion indication echo is achieved indirectly by the detection of lost packets. With ECN, the congestion is indicated by setting the CE bits (see below) at an IP packet and is echoed back by the receiver to the transmitter by setting proper bits in the Transport Layer's protocol header. For example, when using TCP, the congestion indication is echoed back by setting the ECE bit (see below).
Read more about this topic: Explicit Congestion Notification
Famous quotes containing the word operation:
“Waiting for the race to become official, he began to feel as if he had as much effect on the final outcome of the operation as a single piece of a jumbo jigsaw puzzle has to its predetermined final design. Only the addition of the missing fragments of the puzzle would reveal if the picture was as he guessed it would be.”
—Stanley Kubrick (b. 1928)
“Human knowledge and human power meet in one; for where the cause is not known the effect cannot be produced. Nature to be commanded must be obeyed; and that which in contemplation is as the cause is in operation as the rule.”
—Francis Bacon (1560–1626)
“It requires a surgical operation to get a joke well into a Scotch understanding. The only idea of wit, or rather that inferior variety of the electric talent which prevails occasionally in the North, and which, under the name of “Wut,” is so infinitely distressing to people of good taste, is laughing immoderately at stated intervals.”
—Sydney Smith (1771–1845)