H Alvaro, Could you look at version -05 which is intended to resolve your DISCUSS as discussed below.
Thanks, Donald =============================== Donald E. Eastlake 3rd +1-508-333-2270 (cell) 155 Beaver Street, Milford, MA 01757 USA [email protected] On Tue, Feb 21, 2017 at 2:33 PM, Donald Eastlake <[email protected]> wrote: > Hi Alvaro, > > On Thu, Jan 19, 2017 at 9:18 AM, Alvaro Retana (aretana) > <[email protected]> wrote: >> Donald: >> >> Hi! >> >> I am not concerned about the case you described below: where the source and >> destination are attached to the same switch. Nor am I concerned about >> transit TRILL data packets. > > OK. I guess I was mislead by your reference to the IS-IS standard that > a router in overload "shall not" be considered for transit. I thought > that your comment had to do with building shortest cost paths which is > not particularly relevant here. > >> I am concerned about the case where the other end stations are not attached >> to any of the local switches, but are somewhere else in the campus (or the >> mixed case where some of the other end stations are attached to an >> overloaded switch, but others are elsewhere). In that case, if I am not >> missing anything, the appointed forwarder for the local link will accept the >> native frame and will have to send a TRILL Data Packet across the campus – >> the information to do that may not be available if the switch is overloaded. > > Yes. The case you cite is one where the designated router really, as > the draft says, SHOULD NOT appoint the router in overload as appointed > forwarder. (Note that if it violates this "SHOULD NOT" the appointed > forwarder becomes, as far as IS-IS routing is concerned, a source and > sink, not a transit node.) But, in any case, it may be that the > designated router on the link is the only router on the link and is in > overload or it may be that all the routers on the link are in > overloaded or it may be the case I cite where the best routed to > appointer forwarder for VLAN-x is one that is in overload because all > the end stations in VLAN-x are attached to that router. So there are > plenty of cases where either it is a good idea or is unavoidable to > appoint a router in overload as the appointed forwarder for some VLAN. > You ask for the reason the draft says "SHOULD NOT" rather than "MUST > NOT" and that's the reason. > > I can make some changes to Section 2.4 to try to clarify this. > > Thanks, > Donald > =============================== > Donald E. Eastlake 3rd +1-508-333-2270 (cell) > 155 Beaver Street, Milford, MA 01757 USA > [email protected] > >> Thanks! >> Alvaro. >> >> >> >> On 1/18/17, 11:43 PM, "Donald Eastlake" <[email protected]> wrote: >> >> >> >> Hi Alvaro, >> >> >> >> On Wed, Jan 18, 2017 at 3:32 PM, Alvaro Retana <[email protected]> wrote: >> >> Alvaro Retana has entered the following ballot position for >> >> draft-ietf-trill-rfc6439bis-04: Discuss >> >> >> >> When responding, please keep the subject line intact and reply to all >> >> email addresses included in the To and CC lines. (Feel free to cut this >> >> introductory paragraph, however.) >> >> >> >> ---------------------------------------------------------------------- >> >> DISCUSS: >> >> ---------------------------------------------------------------------- >> >> >> >> Section 2.4 (Overload and Appointed Forwarders) talks about potential >> >> Appointed Forwarders which are overloaded. In IS-IS, a node with the >> >> overload bit set "shall not" (ISO 10589) be considered for transit. >> >> However, the use of "SHOULD NOT appoint an RBridge in overload" and >> >> "SHOULD re-assign VLANs from the overloaded RBridge" leaves a potential >> >> hole in the proper forwarding of TRILL data packers. Why aren't MUST >> >> NOT/MUST used? Is there something in the specific use of IS-IS by TRILL >> >> that I am missing? >> >> >> >> The Appointed Forwarder function has to do with accepting frames from >> >> end stations for ingress and egressing frames to end stations. It does >> >> not have anything to do with TRILL Data packet transit routing. >> >> >> >> Consider the following case: two TRILL switches (RBridges) RB1 and RB2 >> >> are connected by a link L1 that also has end stations on it. The end >> >> stations are all in VLAN X. There are other end stations in VLAN X in >> >> the TRILL campus not on L1 but all of these other end stations are >> >> directly connected to RB2. RB2 is in overload. >> >> >> >> Under these circumstances, RB2 should be the Appointed Forwarder for >> >> VLAN X as that way traffic between all of the VLAN X end stations can >> >> be forwarded by RB2 without any IS-IS routing at all. RB2 will just >> >> be, in effect, forwarding native frames between RB2 ports (although, >> >> for consistency, the TRILL specifications say that RB2 ingresses this >> >> VLAN X traffic by encapsulating it into a TRILL Data frame, and then >> >> notices it is destined for an end station on a local port, immediately >> >> decapsulates it, and sends it out that port). >> >> >> >> I think this should be an easy DISCUSS to clear; either point to the >> >> piece I'm missing, or don't use an overloaded node. >> >> >> >> Thanks, >> >> Donald >> >> =============================== >> >> Donald E. Eastlake 3rd +1-508-333-2270 (cell) >> >> 155 Beaver Street, Milford, MA 01757 USA >> >> [email protected] >> >> _______________________________________________ trill mailing list [email protected] https://www.ietf.org/mailman/listinfo/trill
