[HSSG] Jumbo Thursday

[Joel Goergen <joel@xxxxxxxxxxxxxxxxxxx>]

Title:

Wow, I guess it really doesn't pay to take a day off!  Yesterday should go down as 'Jumbo Thursday'.

Rather then respond to individuals, thought I would sum it all up and hit each item.

1. Latency
2. Betrayal and inappropriate use of the process
3. Kevin, Brad, Geoff, Shimon, and maybe Howard say 'no' to jumbos in HSSG
4. Research Community asks for clarification of the question ... to jumbo or not to jumbo ...

1. Latency : Do Jumbos add latency in a store and forward implementation?
To some degree, I agree with Pat on this issue.  In a small scale system or merchant silicon application, latency is a problem with jumbo frames and does increase with usage. 
In a high density core or edge implementation with specific memory techniques deployed in a network application engineered for jumbo frames, no .... any latency added is negligible.  Check out available statistics for high end core implementations.

2. Betrayal and inappropriate use of the process
WOW ... not sure where that came from.  I thought this was a forum for discussion around HSSG.  Are we going to accuse everyone of this?  If we are, it sure is going to make things difficult.

3. Kevin, Brad, Geoff, Shimon, and maybe Howard say 'no' to jumbos in HSSG
Good for you all!  It so happens that I agree with you in principle. 

I didn't ask the question to be the one that brings it up every few years.  I asked the question for very relevant reasons ... the least of which is every customer technical discovery I am involved in, the RFQ always contains "Jumbo Support ... check YES or NO".

I also worry about compatibility .. I don't want to see anyone have to redesign systems or silicon because of what I perceive a documentation procedure.

4. Research Community asks for clarification of the question ... to jumbo or not to jumbo ...
My original question: My question is not whether to support jumbos, because we all already do ... my question is should we finally spec it out?  I think we should, at a minimum, provision for it.

Menachem, Michael, and Marcus ... thanks for giving me the benefit of the doubt and asking to expand on my point of view.  As a research scientist, I greatly appreciate it!

In 10Gbps and higher speeds, there are many of us that need to support jumbo frames for various customer engineered applications.  In some ways, it's like MPLS in that most don't need it but still want it or want to use it in some application specific area in their network.  Shimon eluded to this in his comments.

If I look at the data pipe from the input of the PMD to the input of the NPU for 10Gbps implementations, there are four basic interfaces used: XAUI, XFI, XGMII, and SFI.  The last three interfaces have no physical implications or limitations to jumbo frames.  XAUI (no disrespect intended as it is a great interface and I fully support it ), because of the alignment concept, may drop a frame after the fifth extended frame when deployed in an async environment.  The XAUI interface was never intended to support extended frames, but can be used to do so when careful of the clock distribution.  But it doesn't always work in all extended frame implementations..

My question comes about because there are many people within HSSG considering an architecture composed of multiple Nx10Gbps links in some phy aggregation concept to give us higher speeds.  I'm not naive here.  A serial 100Gbps pipe, end to end, is not likely for a few years ... just like XFI took a bit of work before it's debut.  What I worry is that 'IF' we deploy a XAUI like concept across this phy aggregation concept, none of us will be able to supply extended frames to our customers in the fashion we do so today - out of bounds of the standard, but easy to do so because three of the four interface available allow for it.

I'm not so much interested in specifying jumbo frames as I am in an objective or motion that allows for an interface implementation that does not preclude the use of jumbo frames.  No plot, no hidden agenda ... I just wanted those of us that have to deploy frame extension a mechanism to do so.

-joel