Re: [Isis-wg] Proposed Changes in draft-ietf-isis-segment-routing-extensions
Hannes Gredler <hannes@juniper.net> Thu, 26 March 2015 21:37 UTC
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Date: Thu, 26 Mar 2015 22:36:46 +0100
From: Hannes Gredler <hannes@juniper.net>
To: Uma Chunduri <uma.chunduri@ericsson.com>
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Cc: "isis-wg@ietf.org list" <isis-wg@ietf.org>, "Stefano Previdi (sprevidi)" <sprevidi@cisco.com>, "draft-ietf-isis-segment-routing-extensions@tools.ietf.org" <draft-ietf-isis-segment-routing-extensions@tools.ietf.org>
Subject: Re: [Isis-wg] Proposed Changes in draft-ietf-isis-segment-routing-extensions
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hi uma, don't you have concerns that fragment-0 might get a too crowded space ? /hannes On Thu, Mar 26, 2015 at 07:34:51PM +0000, Uma Chunduri wrote: | Dear Stefano and authors, | | Proposed modifications (though not exact text) are very thoughtful | and IMO this is really good and I don't see any backward compatibility issues | (I didn't see many vendors yet advertise multiple SRGBs). | | >Therefore a possible option is to restrict the advertisement of | >multiple srgb's into the SAME SR-Cap SubTLV where flags get | >defined once and srgb ranges encoded within the same (unique) | >SR-Cap SubTLV (btw, we still have room for up to 27 srgb ranges). | | "SAME" ==> fragment-0 perhaps this would ensure SRGB is ALWAYS there (as this is critical for SR to even begin) | in the same fragment regardless on non-zero fragments have any data which are and can change, | shrink etc.. (may be it could be too restrictive, but if this is to be considered this is the best time)? | | And I have posted my comments earlier on flags to be changed to MT-ID and yet to see response and | changes surrounding the same. | | -- | Uma C. | | -----Original Message----- | From: Isis-wg [mailto:isis-wg-bounces@ietf.org] On Behalf Of Stefano Previdi (sprevidi) | Sent: Wednesday, March 25, 2015 6:42 AM | To: isis-wg@ietf.org list | Cc: draft-ietf-isis-segment-routing-extensions@tools.ietf.org | Subject: [Isis-wg] Proposed Changes in draft-ietf-isis-segment-routing-extensions | | All, | | The authors of draft-ietf-isis-segment-routing-extensions would like to expose the following proposed changes to SRGB advertisement which are being considered. | | 1. Single Vs. Multiple SRGB ranges | Currently, section 3.1. SR-Capabilities Sub-TLV defines that: | | "A router not supporting multiple occurrences of the SR-Capability | sub-TLV MUST take into consideration the first occurrence in the | received set." | | The authors would like to remove above text so that a compliant | implementation MUST support the receiving of multiple ranges. | | 2. Encoding the SR-Cap in a single LSP Fragment Vs. Single TLV | Currently, section 3.1. SR-Capabilities Sub-TLV defines that: | | "The SR Capabilities sub-TLV (Type: TBD, suggested value 2) MAY | appear multiple times inside the Router Capability TLV and has | following format [...]" | | and | | "Only the Flags in the first occurrence of the sub-TLV are to be | taken into account" | | and | | "The originating router MUST encode ranges each into a different | SR-Capability sub-TLV and all SR-Capability TLVs MUST be encoded | within the same LSP fragment." | | and | | "The order of the ranges (i.e.: SR-Capability sub-TLVs) in the | LSP fragment is decided by the originating router and hence the | receiving routers MUST NOT re-order the received ranges. This | is required for avoiding label churn when for example a | numerical lower Segment/Label Block gets added to an already | advertised Segment/Label Block." | | Authors agreed that: | . the encoding scheme is suboptimal and doesn't make best use of | the TLV/LSP space (e.g.: flags field is replicated and unused). | . we want to preserve the requirement of NOT sorting the received | srgb ranges in order to avoid churns and downtime when a change | is advertised (typically when the srgb is extended). | | Therefore a possible option is to restrict the advertisement of | multiple srgb's into the SAME SR-Cap SubTLV where flags get | defined once and srgb ranges encoded within the same (unique) | SR-Cap SubTLV (btw, we still have room for up to 27 srgb ranges). | | Now, doing this will improve the encoding and clarity of the spec | but introduces a backward compatibility issue with current | version of the draft. Therefore it is important that all | implementors make themselves known and tell the authors how | difficult this change is from an implementation perspective. | | Among the authors we have 4 implementors for which the change | seems not to be a problem but other implementations of ISIS, | Segment Routing extension may exists and so it is necessary to | check whether anyone has a problem with the proposed change. | | Thanks. | s. | | _______________________________________________ | Isis-wg mailing list | Isis-wg@ietf.org | https://www.ietf.org/mailman/listinfo/isis-wg | | _______________________________________________ | Isis-wg mailing list | Isis-wg@ietf.org | https://www.ietf.org/mailman/listinfo/isis-wg
- [Isis-wg] Proposed Changes in draft-ietf-isis-seg… Stefano Previdi (sprevidi)
- Re: [Isis-wg] Proposed Changes in draft-ietf-isis… Uma Chunduri
- Re: [Isis-wg] Proposed Changes in draft-ietf-isis… Hannes Gredler
- Re: [Isis-wg] Proposed Changes in draft-ietf-isis… Les Ginsberg (ginsberg)
- Re: [Isis-wg] Proposed Changes in draft-ietf-isis… Chris Bowers
- Re: [Isis-wg] Proposed Changes in draft-ietf-isis… Pushpasis Sarkar
- Re: [Isis-wg] Proposed Changes in draft-ietf-isis… Uma Chunduri
- Re: [Isis-wg] Proposed Changes in draft-ietf-isis… Les Ginsberg (ginsberg)
- Re: [Isis-wg] Proposed Changes in draft-ietf-isis… Uma Chunduri
- Re: [Isis-wg] Proposed Changes in draft-ietf-isis… Uma Chunduri
- Re: [Isis-wg] Proposed Changes in draft-ietf-isis… Stefano Previdi (sprevidi)
- Re: [Isis-wg] Proposed Changes in draft-ietf-isis… Hannes Gredler
- Re: [Isis-wg] Proposed Changes in draft-ietf-isis… Les Ginsberg (ginsberg)
- Re: [Isis-wg] Proposed Changes in draft-ietf-isis… Ahmed Bashandy
- Re: [Isis-wg] Proposed Changes in draft-ietf-isis… Henderickx, Wim (Wim)
- Re: [Isis-wg] Proposed Changes in draft-ietf-isis… Pushpasis Sarkar
- Re: [Isis-wg] Proposed Changes in draft-ietf-isis… Les Ginsberg (ginsberg)
- Re: [Isis-wg] Proposed Changes in draft-ietf-isis… Chris Bowers
- Re: [Isis-wg] Proposed Changes in draft-ietf-isis… Les Ginsberg (ginsberg)
- Re: [Isis-wg] Proposed Changes in draft-ietf-isis… Pushpasis Sarkar
- Re: [Isis-wg] Proposed Changes in draft-ietf-isis… Stefano Previdi (sprevidi)
- Re: [Isis-wg] Proposed Changes in draft-ietf-isis… Ahmed Bashandy
- Re: [Isis-wg] Proposed Changes in draft-ietf-isis… bruno.decraene
- Re: [Isis-wg] Proposed Changes in draft-ietf-isis… Stefano Previdi (sprevidi)
- Re: [Isis-wg] Proposed Changes in draft-ietf-isis… Les Ginsberg (ginsberg)
- Re: [Isis-wg] Proposed Changes in draft-ietf-isis… Henderickx, Wim (Wim)
- Re: [Isis-wg] Proposed Changes in draft-ietf-isis… Jeff Tantsura
- Re: [Isis-wg] Proposed Changes in draft-ietf-isis… bruno.decraene
- Re: [Isis-wg] Proposed Changes in draft-ietf-isis… Uma Chunduri
- Re: [Isis-wg] Proposed Changes in draft-ietf-isis… Stefano Previdi (sprevidi)
- Re: [Isis-wg] Proposed Changes in draft-ietf-isis… stephane.litkowski