Roberto Baldessari wrote:
Hi Fred,
Thanks for writing this down.
As I said privately, I agree. "sub-IP" is definitely more general and
less confusing than 2.5.
I'm sometimes comfortable calling that a MAC layer instead of sub-IP.
Exceptions are some links which don't have MAC layers.
Alex
regards,
Roberto
-----Original Message----- From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Templin, Fred L
Sent: Thursday, March 22, 2007 10:24 PM To: [EMAIL PROTECTED] Cc:
[EMAIL PROTECTED] Subject: [Manemo] the layer below IP
I made a rather strong statement with an individual during a
meeting this week that really should more appropriately have been
vetted with the rest of the community instead - so, here I am.
In the classic model, we have traditionally considered the layer
immediately below IP (L3) as the link layer (L2). But, in some
common scenarios there is actually quite a lot that goes on below
IP but above the datalink. Some have called this "L2.5", but I find
that term to be misleading because it seems to imply that there is
one and only one functional layer between L3 and L2 and that does
not accurately capture all scenarios.
I wrote a draft that tried to address this by re-introducing the
legacy OSI terminology which specified a 3 sublayer decomposition
of L3 (the internet sublayer (L3c), the subnet enhancement sublayer
(L3b) and the subnet access sublayer (L3a)). But, even this more
specific terminology suffers from hazy distinctions between what
belongs in one of the sublayers as opposed to another.
So, can we simply call it the "sub-IP layer" as opposed to the
other alternatives? "Sub-IP" makes no statement about any layering
structure that may occur immediately below IP, and as such it
allows for any level of mechanisms that may need to be implemented
below IP down to and including the (classical) link layer. The term
can also be used even if there is no intermediate mechanism at all,
since L2 is by definition a "sub-IP" layer.
In summary, I belive there is no one precise way to call the
mechanisms that might occur immediatley below IP so can we just
collectively call them:
The "sub-IP layer"
Thanks - Fred [EMAIL PROTECTED]
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