Re: FW: [802.1] MSTP MIB - mstpMapTable

[Harrie Hazewinkel <harrie@lisanza.net>]

Romascanu, Dan (Dan) wrote:
> This issue popped-up on the IEEE 802.1 WG list, around a OCTET STRING
> object that would exceed 500 octets, and the authors decided to break it
> into 'smaller pieces'. 
> While watching this discussion I checked with the MIB review guidelines,
> which do not say anything about a recommended size limiting of an OCTET
> STRING, excepting the fact that it is recommended to be limited at some
> size, especially when the OCTET STRING object is an index. See
> http://www.ietf.org/internet-drafts/draft-ietf-ops-mib-review-guidelines
> -04.txt Section 4.6.1.4. Is this OK? If so, how does this live together
> with Keith's comment? 

I do not see a real problem here.

Immagine, cars should be smaller then 2.5 meters wide, since
otherwise the lanes on the road will not wide enough. If you
live in a small italian town with old roads the car may not
exceed 1.9 meters width, since you would otherwise not be
able to go into the little village.
Even though, the little village adds extra limitations to the
width of the car, it does not forbid it. It only cannot
go into the little village.

Therefore, I do see the limitations of the size of an OCTET
STRING is still as defined by ASN.1. However, if you use
some transport mappings extra limitations may apply.

One might argue that this is confusing to MIB designers
and a hint might have been given about it.


> Dan
>
>
>  
>
> -----Original Message-----
> From: IEEE 802.1 [mailto:hdk-0119.ckxbsg@ATT.NET] On Behalf Of Keith
> McCloghrie
> Sent: Tuesday, September 06, 2005 3:45 PM
> To: STDS-802-1-L@listserv.ieee.org
> Subject: Re: [802.1] MSTP MIB - mstpMapTable
>
>
> > 1. Divide one long OCTET STRING into 4 shorter
> >    OCTET STRING. I don't see the reason for it.
>
>
> The reason is the difference between "must" and "recommended".
> Specifically, all the transport mappings in RFC 3417 say the equivalent
> of:
>
>    When an SNMP entity uses this transport mapping, it must be capable
>    of accepting messages up to and including 484 octets in size.  It is
>    recommended that implementations be capable of accepting messages of
>    up to 1472 octets in size.  Implementation of larger values is
>    encouraged whenever possible.
>
> Keith.
>
> IEEE 802.1 list:
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Harrie

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