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Another example of the pause function exists when
the server (in the ASCII figure below) operates in
a WAN environment over SONET OC-192 (at 9.95328Gbps).
The server would be required to implement the WIS
function or equivalent ELTE functionality and would
have to throttle bandwidth from the remote machine
through PAUSE frames.
University of Ottawa
From: Stephen Bates
To: Gavin Parnaby
Sent: 2/20/04 10:55 AM
Subject: RE: [10GBASE-T] latency
Gavin and Serag
Gavin, thanks for that overview of the PAUSE functionality. One question
I have is does anyone know if PAUSE is implemented end-to-end or
hop-by-hop in an Ethernet connection between source and sink via one or
more switches? Also, what is the primary method of flow control when the
following scenario occurs?
machine A <-- Speed A --> Switch <-- Speed B --> Server
My concern is if speed A is < Speed B (e.g. A=1000BASE-T and
B=10GBASE-T) and we use PAUSE to ensure flow control then 10GBASE-T may
have to include PAUSE. If not then buffers in the switch will overflow
when machine A requests a large amount of data from the server. Perhaps
flow control in a switch with multi-speed ports is handled using
something other than PAUSE? I am assuming this is a low level switch and
TCP is not used to do flow control, is this correct?