R: [ns] queue limit

["Alfredo Grieco" <alfredogr@libero.it>]

>On Monday 16 July 2001 12:45, Alfredo Grieco wrote:
>> Hi at all,
>> what is the meaning of queue-limit over the queue of the first link
>> of a connection? Is the limit able to create congestion?
>
>Every node you create has a queue.  Every queue has a limited amount
>of space.  If you have a long fat network and big receive window
>size, your sending node can put out a burst of packets too large for
>its own queue to handle.  The packets will be dropped before they
>"officially" get onto the network.
>
>Here is an informal, contrived example.  Node A is transmitting to
>node B.  A sends 50 packets to B.  B receives all of the packets and
>sends back 50 ACKs.  Due to other network traffic, all of the ACKs
>get compressed on a router.  When the traffic backlog clears, 50 ACKs
>get bursted to A.  Every time A gets an ACK, it puts out another
>packet.  A can only hold 30 packets in its internal queue; if it gets
>the 50th ACK before it can get 20 packets onto the wire, then one or
>more packets must be dropped from A's queue.
>
thanks for the simple and effective answer,
if the sender uses TCP, the 20 packets dropped in your example are
retransmitted later ?
Alfredo