[Diffserv-interest] Fwd: Re-usability of DIFFSERV MIB
Brian E Carpenter <brian@hursley.ibm.com> Fri, 04 April 2003 14:36 UTC
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Date: Fri, 04 Apr 2003 16:37:26 +0200
From: Brian E Carpenter <brian@hursley.ibm.com>
Organization: IBM
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Subject: [Diffserv-interest] Fwd: Re-usability of DIFFSERV MIB
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On behalf of Bert... Subject: Re-usability of DIFFSERV MIB Date: Fri, 4 Apr 2003 15:12:15 +0200 From: "Wijnen, Bert (Bert)" <bwijnen@lucent.com> To: diffserv@ietf.org FYI and possible (re-)action. Thanks, Bert -----Original Message----- From: Woundy, Richard [mailto:Richard_Woundy@cable.comcast.com] Sent: donderdag 3 april 2003 0:58 To: 'Wilson.Sawyer@arrisi.com'; Wijnen, Bert (Bert) Cc: ipcdn@ietf.org Subject: RE: [ipcdn] Re: Status - draft-ietf-ipcdn-subscriber-mib-10.txt Wilson and Bert, One immediate issue I found, in trying to re-use the DiffServ MIB for the DOCSIS Subscriber Management functionality, was in the structure of the Data Path table, which is the initial table for packet classification. The Data Path Table is the first lookup table in the DiffServ MIB, and it uses ifIndex and ifDirection as the initial parameters to match. Upon a match, the typical next table is the Classifier Table (although the entry may point to other Tables in the MIB). In the Subscriber Management MIB, the first lookup table is docsSubMgtCmFilterTable, which uses the particular cable modem, upstream or downstream direction (similar to ifDirection), and CM versus CPE (CPEs are behind the CMs on the subscriber home network) source/target to map to a filter-group. The filter-group points to a set of rows in the docsSubMgtPktFilterTable for packet classification. The four subscriber management filter-groups are configured through the DOCSIS 1.1/2.0 CM registration processes. The two gaps I see in DiffServ MIB functionality are: 1. The DiffServ MIB assumes that a uniform set of classifiers are applied to all traffic flowing over a particular interface, because in the general network case, one cannot differentiate traffic except by classification. The Subscriber Management MIB assumes that distinct sets of classifiers are applied to different groups of cable modems that co-exist on the same cable RF interface, because the DOCSIS registration process aids the CMTS in differentiating different CM/CPE traffic sources and sinks. Note that there can be thousands of CMs from different filter-groups co-existing on the same cable RF interface, so an operator would need to add thousands of Classifier Table entries to match on specific CM/CPE sources and sinks. 2. The Subscriber Management MIB differentiates between CM source/sink traffic and CPE source/sink traffic. The CMTS knows the difference between CMs and CPEs on the same cable RF IP subnet(s) via the DOCSIS registration process. Using the current DiffServ MIB, making distinctions between CM and CPE traffic would require many more entries in the Classifier Tables, in order to enumerate the CM source IP addresses. It looks like the DiffServ folks were looking to use more generic parameters than the ifIndex during the development of the MIB. From section 2.2 of RFC 3289: Another possible direction of abstraction is one using a concept of "roles" (often, but not always, applied to interfaces). In this case, it may be possible to re-use the object definitions in this MIB, especially the parameterization tables. The Data Path table will help in the reuse of the data path linkage tables by having the interface specific information centralized, allowing easier mechanical replacement of ifIndex by some sort of "roleIndex". This work is ongoing. I don't know how to apply this "ongoing work" to the immediate issues that are solved by the current Subscriber Management MIB. -- Rich _______________________________________________ Diffserv-interest mailing list Diffserv-interest@ietf.org https://www1.ietf.org/mailman/listinfo/diffserv-interest
- [Diffserv-interest] Fwd: Re-usability of DIFFSERV… Brian E Carpenter