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Re: Jumbo Frames in 10GbE?


Some thoughts on the issue:

1)  If Jumbo Frames are a good thing, they should be applied to all forms of
Ethernet.  Therefore, the HSSG (which is about higher speed links) is not
the correct place.  The 802.3 Working Group is the correct place.  Assuming
there was high interest, we could get a Study Group going to look only at
Jumbo Frames at all Ethernet speeds.

2)  What are Jumbo Frames?  How many bytes of payload?  One manufacturer has
championed 9,000 bytes.  What is to say that this is the correct number?
Remember that we have had previous "industry moves" for efficiency (remember
document scanning systems with 4,096 byte packets?) that have long since bit
the dust.

3)  You are correct that there is a system performance issue.  However, if
you look at the overall system components (of say a workstation or server),
the network connection is generally not the least efficient.  Software
systems usually top the list, with inefficient bus systems and poor system
integration as number two.  For example, at my last shop, we were able to
get the same hardware to pass from 240 Mbps to 700 Mbps depending on the
operating system and driver software used.  Similarly, consider that the
maximum throughput of a 64-bit 66 MHz PCI bus is over 4 Gbps - have you seen
a PCI system giving much above 1 Gbps?

My point here is that we should be tackling the worst inefficiencies first -
the low hanging fruit.  That is not the network connection.   The HSSG job
is not to solve the overall systems inefficiency problem but to solve
inefficiencies that might arise in the network system as we move to 10 Gbps.

Brian MacLeod

-----Original Message-----
From: Joe Gwinn <gwinn@xxxxxxxxxx>
To: Booth, Brad <bbooth@xxxxxxxxxx>
Cc: HSSG_reflector (E-mail) <stds-802-3-hssg@xxxxxxxx>
Date: Monday, June 21, 1999 1:35 PM
Subject: Jumbo Frames in 10GbE?

>At 4:24 PM 99/6/17, Booth, Brad wrote:
>>Just a small point.  One of the objectives that passed with greater than
>>75% in Coeur d'Alene was to "preserve minimum and maximum FrameSize of
>>current 802.3 Std."
>I don't know that the issue is going to stay decided all that long, based
>on the recent article "Jumbo Frames gather support" (Jeff Caruso, Network
>World, 14 June 1999, page 6), which states that IETF has published a
>working document proposing that ethernet frames be made larger than the
>current 1,500-byte maximum, the basic rationale being to reduce the packet
>rate and thus load on packet-handling components of the system.  In short,
>this is a system issue, and cannot really be decided solely at the MAC
>If jumbo frames are to come, 10GbE would be a logical place to start.
>The issue will ultimately be decided by an IEEE Ballot Group, not a
>Plenary.  If the market is really going to bigger packets, as this article
>implies, it will be hard to resist.
>Joe Gwinn
>The above is in response to the following:
>>        >Issues 3 - Bit Error Rate
>>        >The assumption will be that this is 10-12. If someone wishes to
>>        >this they should bring a presentation to the next meeting
>>        detailed reasoning why this needs to change.
>>        It strikes me that the issue of larger maximum packet sizes will
>>        come up, just as it did for GbE.  If 10GbE goes to 9 KB packets,
>>the design
>>        center BER would need to go to 10^-13 to maintain the same
>>        packet loss rate.   I'm not sure how much effect this would have
>>        practice, as most gigabit links achieve much better than 10^-12,
>>if they
>>        work at all.  Anyway, these items are ripe for debate and
>**** end of message ****