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. 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. Thanks! Alvaro. On 1/18/17, 11:43 PM, "Donald Eastlake" <[email protected]<mailto:[email protected]>> wrote: Hi Alvaro, On Wed, Jan 18, 2017 at 3:32 PM, Alvaro Retana <[email protected]<mailto:[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]<mailto:[email protected]>
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