>From my experience, the term "L2.5" (and "MAC layer", although MAC tends to be a more media-specific term, and sometimes "Framing layer") is generally used to refer to behavior that is specific to a given _combination_ of a L2 media type and an L3 protocol.
L2 would generally be behavior that is independent of whether the L3 protocol is IPv4, IPv6, IPX, LLDP, or whatever else. I think this distinction is important. -Dave > -----Original Message----- > From: Alexandru Petrescu [mailto:[EMAIL PROTECTED] > Sent: Monday, March 26, 2007 9:54 AM > To: Roberto Baldessari > Cc: Templin, Fred L; [EMAIL PROTECTED] > Subject: [Int-area] Re: [Manemo] the layer below IP > > 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] > >> > >> _______________________________________________ Manemo mailing list > >> [EMAIL PROTECTED] http://www.mobileip.jp/mailman/listinfo/manemo > >> > > > > _______________________________________________ Manemo mailing list > > [EMAIL PROTECTED] http://www.mobileip.jp/mailman/listinfo/manemo > > > > > ______________________________________________________________________ > This email has been scanned by the MessageLabs Email Security System. > For more information please visit http://www.messagelabs.com/email > ______________________________________________________________________ > > _______________________________________________ > Int-area mailing list > [email protected] > https://www1.ietf.org/mailman/listinfo/int-area _______________________________________________ Int-area mailing list [email protected] https://www1.ietf.org/mailman/listinfo/int-area
