Re: [FE] Frame size poll
Hugh,
You've hit on something I was hoping would surface soon. In your opinion, is there value in trying to determine this "memory tag" (hoping this newly coined term 'memory tag' won't get confused with any other tag) size on existing gear as a means of gauging impact to existing implementations?
I am familiar with implementations that store full frames and have 1,536 octet upper limited limits. This allows 18 octets of memory tag space for max untagged frames or 14 octets of memory tag space for max VLAN tagged frames.
Is a memory tag size of 48 octets a safe upper limit? If so, 2,000 could be the max frame size. 1500 for max data payload and 500 for everything else. Hmmm...sounds like the original Ethernet goal of 1K data payload and 500 odd octets for everything else...
Determining the new max frame size is one question. Deciding if these larger frames will be "enabled" on some links and not others is a separate, but also intesting, question. Perhaps I'll save that for another poll...
Kevin Daines
Chair, 802.3 Frame Expansion Study Group
-----Original Message-----
From: Hugh Barrass [mailto:hbarrass@cisco.com]
Sent: Friday, September 03, 2004 9:25 AM
To: Kevin Daines
Cc: STDS-802-3-FE@LISTSERV.IEEE.ORG
Subject: Re: [FE] Frame size poll
Kevin,
As a hardware designer, my first pick was 2) however I have designed a
number of switch fabrics in various organizations and I have also looked
closely at many others and the 2048 number may pose a problem for some
equipment or architectures. Many shared memory architectures use tags
that are stored along with the frames therefore a frame size of 2048
would mean that the storage quanta would be just over 2k - a "bad"
number. Given that this may be an "architectural" feature rather than an
implementation, it would act as an impediment to rapid development of
compliant solutions using those architectures.
As a result, I would support 1) or 3) with any number up to 2000 (an
arbitrary value, less than 2k). Note, however, that I haven't consulted
any colleagues on this so I cannot say that this response would be
favorable with others in my team.
Hugh.
Kevin Daines wrote:
>All,
>
>
>Now to the poll. Would you prefer:
>
>1) 1875 (which is based on the repeater calculation)
>2) 2048 (a power of 2)
>3) some other number (please specify)
>
>
>