[rbridge] comment about draft-ietf-trill-rbridge-channel-02

[Donald Eastlake]

Hi Anoop,

On 8/17/11, Anoop Ghanwani <anoop at alumni.duke.edu> wrote:
> This pertains to the following text in Section 2.2:
>
>>>>>
> When an RBridge Channel message is originated, the Hop Count field
> defaults to the maximum value, 0x3F, but particular RBridge Channel
> protocols MAY specify other values. For messages sent a known number
> of hops, such as one-hop messages or two-hop neighbor echo messages,
> setting the Hops field to the maximum value and checking the Hop
> Count field on receipt provides an additional validity check as
> discussed in [RFC5082].
>>>>>

The phrase "two-hop neighbor echo messages" above is a bit confusing.
What was meant was an echo that goes to an immediate neighbor and
comes back.

> And then later:
>
>>>>>>
> If the channel message is a multi-hop
> unicast message, then the egress nickname is a nickname of the target
> RBridge; this includes the special case of an "echo" OAM message
> where the originator places one of its own nicknames in both the
> ingress and egress nickname fields.
>>>>>>>
>
> Technically we could have an echo message that has
> both the ingress and egress nicknames the same, or it
> could have them different (i.e. the actual egress RBridge).
> Would it be possible to disambiguate these two?
> Perhaps we could refer to the generic echo message
> as a loopback, and the one with the identical ingress
> and egress nickname as an echo?

I'm not sure we need specific terms here, just better descriptions.
Attached are suggested changes to the text.

Thanks,
Donald
=============================
 Donald E. Eastlake 3rd   +1-508-333-2270 (cell)
 155 Beaver Street, Milford, MA 01757 USA
 d3e3e3 at gmail.com
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Current text

For messages sent a known number of hops, such as one-hop messages or
two-hop neighbor echo setting the Hops field to the maximum value and
checking the Hop Count field on receipt provides an additional
validity check as discussed in [RFC5082].

Suggested text

For messages sent a known number of hops, such as one-hop messages or
a two-hop loop back message through an immediate neighbor RBridge,
setting the Hops field to the maximum value and checking the Hop Count
field on receipt provides an additional validity check as discussed in
[RFC5082].

Current text

If the channel message is a multi-hop unicast message, then the egress
nickname is a nickname of the target RBridge; this includes the
special case of an "echo" OAM message where the originator places one
of its own nicknames in both the ingress and egress nickname fields.

Suggested text

If the channel message is a multi-hop unicast message, then the egress
nickname is a nickname of the target RBridge; this includes the
special case of an OAM message intended to loop back from an immediate
neighbor where the originator places one of its own nicknames in both
the ingress and egress nickname fields.