Rx and Tx buffers

[igorkvaso]

Hi,

could you please explain me, what is the purpose of Rx and Tx buffers? I am googling it for quite a while with no much sucess

as far as I understand, there are 2 types of buffers: SW buffers and HW buffers (Rx and Tx buffers)

packet is put into Tx buffer when it came from SW buffer and is about to be serialised on the link

but I have got no idea what are Rx buffers good for....

also my second question: are Tx and Rx buffers only on routers or switches have them as well?

thanks a lot

[rais]

Transmit and Receive buffers are memory spaces allocated by a router or a switch to handle traffic bursts.

For example, traffic burst could be: all ports trying to send data to a single uplink port on a router/switch. When incoming/outgoing traffic exceeds physical capacity of a switch/router, buffering comes into action. Otherwise data would be dropped. Usually Tx/Rx buffers are implemented using a pool of [shared] memory.

HTH.

[igorkvaso]

the practical consequence of packet bursts are, that:

Rx buffers are used when CPU is overloaded and cannot process any more packets, so new incoming packets are put into Rx buffer?

my question is more like: when is packet put into Rx or Tx buffer?

thanks

[Vasileios Bouloukos MSc, ITIL, CCIE]

Take a look to the next link which answers your question

http://wiki.nil.com/Queuing_Principles_in_Cisco_IOS#Where_to_queue

Hope that helps

Vasilis

[Joseph W. Doherty]

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Posting

Generally they are "special" queues to deal with packets/frames arriving on an interface or waiting to be transmitted on an interface.  What's "special" about them is they often have special hardware support to insure a packet/frame is processed within the real-time requirements of the interface.  Even something as "simple" as the console's serial port generally has special receive/transmit buffers, although for single characters.