RE: Re> Unsupported capability notification
"Natale, Jonathan" <JNatale@celoxnetworks.com> Fri, 12 July 2002 13:50 UTC
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From: "Natale, Jonathan" <JNatale@celoxnetworks.com>
To: 'Bruno Rijsman' <bwarijsman@hotmail.com>, idr@merit.edu
Cc: "Natale, Jonathan" <JNatale@celoxnetworks.com>
Subject: RE: Re> Unsupported capability notification
Date: Fri, 12 Jul 2002 09:50:43 -0400
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Thanks. My question is: Does TXing unsupported capability=C mean: A) I want to RX open with cap. C OR B) I want to RX open without cap. C Before you answer B), which seems to be the obvious answer, please read: ""If a BGP speaker that supports a certain capability determines that its peer doesn't support this capability, the speaker MAY send a NOTIFICATION message to the peer, and terminate peering (see Section "Extensions to Error Handling" for more details). The Error Subcode in the message is set to Unsupported Capability. The message SHOULD contain the capability (capabilities) that causes the speaker to send the message. The decision to send the message and terminate peering is local to the speaker. If terminated, such peering SHOULD NOT be re-established automatically." -- draft-ietf-idr-rfc2842bis-02.txt -----Original Message----- From: Bruno Rijsman [mailto:bwarijsman@hotmail.com] Sent: Friday, July 12, 2002 9:38 AM To: idr@merit.edu Cc: JNatale@celoxnetworks.com Subject: Re> Unsupported capability notification The usage of the unsupported capability notification is widely misunderstood and this is causing real problems in real networks. If you receive a capability code X which you do not recognize, you MUST NOT send back an unsupported capability notification. It is sufficient for you to simply not advertise capability X and as a result the peer will known you do not support capability X. If you receive a capability code Y which you do recognize but for some reason you do not want to use capability Y on that session you SHOULD NOT send back an unsupported capability notification. It is sufficient for you to simply not advertise capability Y and as a result the peer will knwon you do not support capability Y. I known of only one case where the sending of an "unsupported capability" notification is justified: if both sides propose the multi-protocol capability but the proposed set of AFI/SAFIs is completely disjunct. There are many implementations out there that send "unsupported capability" notifications when they should not. For example, there is one widely deployed implementation that sends an "unsupported capability" notification when it receives the four-octet-as-numbers capability. Even worse: this implementation sends the notification without any data (i.e. we don't know which is the offending capability) and often sends the notification before the open (i.e. we can't guess which capabilities they support by looking at their open). --- Original message --- "If a BGP speaker that supports a certain capability determines that its peer doesn't support this capability, the speaker may send a NOTIFICATION message to the peer, and terminate peering. The Error Subcode in the message is set to Unsupported Capability. The message should contain the capability (capabilities) that causes the speaker to send the message. The decision to send the message and terminate peering is local to the speaker. Such peering should not be re- established automatically" --RFC2842, "Capabilities Advertisement with BGP-4" This sounds like: if rtrA is doing capC and rtrB is not doing CapC, then rtrA will send an UnsupCapNotifErrorSubcode=capC ...so if you were to send UnsupCapNotifErrorSubcode=capC then you would/could/should re-open with the offending capability It seems to me that it should be: if rtrA is doing capC and rtrB is not doing CapC, then ***rtrB*** will send an UnsupCapNotifErrorSubcode=capC ...so if you were to ***receive*** UnsupCapNotifErrorSubcode=capC then you would/could/should re-open without the offending capability Thoughts? Thank you very much for your time. _________________________________________________________________ MSN Photos is the easiest way to share and print your photos: http://photos.msn.com/support/worldwide.aspx
- Re> Unsupported capability notification Bruno Rijsman
- RE: Re> Unsupported capability notification Natale, Jonathan
- RE: Re> Unsupported capability notification Bruno Rijsman
- RE: Re> Unsupported capability notification Abarbanel, Benjamin
- Re: Unsupported capability notification Mathew Richardson
- RE: Re> Unsupported capability notification Natale, Jonathan
- RE: Re> Unsupported capability notification Abarbanel, Benjamin
- RE: Re> Unsupported capability notification Tsillas, Jim