Subject: [rbridge] Inner/Outer versus Data/Transport

From: Donald.Eastlake at motorola.com (Eastlake III Donald-LDE008)
Date: Tue, 3 Jul 2007 10:51:19 -0400

Hi,

A terminology question has come up concerning the current use of Inner
and Outer in the protocol specification.

Currently these words are used in a way pretty close to their usual
English meaning. When a frame is being transported inside a TRILL
Header, the Ethernet header on the outside of the frame is called the
Outer header and the one inside the envelope is called the Inner header.
But, when talking about a native frame, what will become the Inner
header when encapsulated is also called an Outer header, because it is
on the outside of the native frame.

This doesn't bother me and I suspect is fine for native English speakers
because the inside/outside connotation of Inner and Outer override any
problem with the same header fields being called Outer when they are at
the start of a native frame and Inner when they are inside a TRILL
envelope.

However, some find this very confusing. For example, consider someone
implementing an Rbridge where the VLAN associated with an incoming frame
is considered meta data stored in a register/variable separate from but
associated with the frame payload. (The VLAN might come from an Outer
VLAN Tag or be assigned based on the port, etc.) What are you going to
call this register/variable? If the incoming frame is a native frame
then, if it is encapsulated, this VLAN tag information will appear in
the "Inner VLAN" position. But if the frame is forwarded in native form
to another local link, it will appear in the "Outer VLAN" position. So
neither Inner nor Outer seems to be an appropriate name for this
hypothetical register/variable.

It has been suggested that "Inner" be changed to "Data" and "Outer" be
changed to "Transport" for TRILL frames and to "Data" from native
frames, or some similar change. I think that such naming would be
reasonably clear and would have the effect that, for example, the Data
VLAN Tag could be called that whether it appeared on the outside of a
native frame or inside a TRILL envelope. 

I don't really care one way or the other and am soliciting working group
opinion on this question.

Thanks,
Donald

---

From: touch at ISI.EDU (Joe Touch)
Date: Tue, 03 Jul 2007 19:18:57 -0700

Eastlake III Donald-LDE008 wrote:
> frames, or some similar change.

Transport has a meaning in the IETF, and this isn't it - even when
encapsulated, the inner header isn't the transport header.

> I think that such naming would be

I think the terms we have are fine, and that diagrams that clarify what
they mean are sufficient. Introducing new terms is as likely to cause
confusion with the currently non-confused as it would be to resolve
confusion in the confused.

Joe

-- 
----------------------------------------
Joe Touch
Sr. Network Engineer, USAF TSAT Space Segment

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 250 bytes
Desc: OpenPGP digital signature
Url : http://mailman.postel.org/pipermail/rbridge/attachments/20070703/22a67160/signature.bin