Re: [trill] Query on Interested VLANsand Spanning Tree Roots Sub-TLV in RFC6326
Donald Eastlake <d3e3e3@gmail.com> Sat, 25 August 2012 02:48 UTC
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From: Donald Eastlake <d3e3e3@gmail.com>
Date: Fri, 24 Aug 2012 22:48:20 -0400
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To: wenyu zou <nkzouwenyu@gmail.com>
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Cc: trill@ietf.org
Subject: Re: [trill] Query on Interested VLANsand Spanning Tree Roots Sub-TLV in RFC6326
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Hi Wenyu, On Fri, Aug 24, 2012 at 9:19 PM, wenyu zou <nkzouwenyu@gmail.com> wrote: > Hi Authors, > I have a question about "AppointedForwarder Status Lost Counter" > in"Interested VLANs and Spanning Tree Roots Sub-TLV", as specified in > [RFC6326], Section 2.3.6. The counter is shared by VLANs from > VLAN.start toVLAN.end. But the counter for per-VLAN can easily be > different by configuration or topology change. When a port lost the > status of being an appointed forwarder for VLANx, the Sub-TLV should > be splited. So it maybe have so many Interested VLANs and Spanning > Tree Roots Sub-TLV in LSPs, and they have little chance to merge > again. > Is it correct? Do you have some method to solve this problem? The Appointed Forwarder Status Lost Counter is a mechanism to optimize data plane learning by trimming the expiration timer for learned addresses per VLAN under some circumstances. (1) If you don't care about that optimization and don't mind some time outs being longer than they otherwise would be, you can just not bother changing the counter, even if you are using data plane learning. On the other hand, if you don't care about sone time outs being shortened when they otherwise wouldn't, you could increment the counter for multiple VLANs even you don't lose AF status on a port for all those VLANS. (2) If you are using ESADI or Directory Assist and not learning from the data plane, the counter doesn't matter and there really isn't any reason to increment it. (3) If an RBridge port has been configured with the "disable end station traffic" bit on (also known as the trunk bit), then it makes no difference if that port is appointed forwarder or not. So there is no reason to increment the counter if such a port loses Appointed Forwarder status. (4) If you are updating the counter, incrementing it by more than one (even up to incrementing it by a couple of hundred), so that it matches the counter for some other VLAN for the same RBridge would have an extremely small probability of causing any sub-optimization and if it did will just very rarely fail to specially decrease the time out for some learned addresses. Thanks, Donald ============================= Donald E. Eastlake 3rd +1-508-333-2270 (cell) 155 Beaver Street, Milford, MA 01757 USA d3e3e3@gmail.com > Thanks. > Regards, > wenyu
- [trill] Query on Interested VLANsand Spanning Tre… wenyu zou
- Re: [trill] Query on Interested VLANsand Spanning… Donald Eastlake