Re: [pcp] #74 (third-party-id-option): Mohamed Boucadair's comments on draft-ietf-pcp-third-party-id-option-00

[Juergen Quittek <[e-mail]>]

Hi Med,

> -----Original Message-----
> From: pcp [mailto:[e-mail]] On Behalf Of
> [e-mail]
> Sent: Freitag, 9. Januar 2015 07:57
> To: Dave Thaler; Andreas Ripke; [e-mail]
> Subject: Re: [pcp] #74 (third-party-id-option): Mohamed Boucadair's comments
> on draft-ietf-pcp-third-party-id-option-00
> 
> Hi Dave,
> 
> Hmm...but what will be the behavior of the server if it is not designed to
> support a length included in the PCP request? Should it truncate the fiele?

Hi Med. This case is pretty clear. Of course it should not truncate an ID. 
If a server cannot support an ID sent to it, the ID is obviously unsuited 
and it should return an error message.

> Shouldn't this will lead to some side effects such as encountering errors to send
> a response or to validate the response at the client side because the content of
> the THIRD_PARTY_ID as included in the response does not match what has
> been included in the response, etc.?

If a server implements the THIRD_PARTY_ID, it needs to implement 
PCP variable length options and be able to return them in an error 
message.

> For these reasons and also to help the design of PCP server, I do still think a
> max should be included as part of the specification. 128 octets seems
> reasonable.

The PCP protocol supports variable length options. 
Are you talking about PCP servers that do not support them?

Best regards,
     Juergen

> Cheers,
> Med
> 
> -----Message d'origine-----
> De : Dave Thaler [mailto:[e-mail]]
> Envoyé : vendredi 9 janvier 2015 02:37
> À : BOUCADAIR Mohamed IMT/OLN; Andreas Ripke; [e-mail]
> Objet : RE: [pcp] #74 (third-party-id-option): Mohamed Boucadair's comments
> on draft-ietf-pcp-third-party-id-option-00
> 
> Andreas Ripke writes:
> > Med's comments contain two technical modifications.
> >
> > 1. A recommended fixed maximum option length of 128 octets.
> >
> > Why should we (unnecessarily?) set an explicit limit to this option?
> > The fixed option length (16 octets) was changed to a variable length with the
> > current draft version.
> > The maximum PCP packet size is 1100 octets and the client must ensure not
> to
> > cause an overrun according to RFC6887.
> > But then, in RFC7220 the maximum variable length for the description option
> is
> > limited to 1016 octets.
> > Is there any special reason to have an explicit maximum option length
> defined?
> >
> > [Med] Fixing a maximum is required to help dimensioning the server and to
> > avoid exhausting server's resources. Most of the identifiers I'm aware of
> don't
> > exceed 128 octets. Hence my recommendation to use that maximum.
> 
> My personal opinion on the above is that the other limits Andreas mentions
> are already sufficient and we don't need to specify a shorter limit than what
> you naturally get.
> 
> -Dave
> 
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