Re: I-D Action:draft-ietf-6man-exthdr-02.txt

[Suresh Krishnan <[e-mail]>]

Hi John,

On 11-03-15 09:25 AM, John Leslie wrote:
> Suresh Krishnan <[e-mail]> wrote:
>> On 11-03-14 06:55 PM, John Leslie wrote:
>>>   I notice that Section 4 calls for TLV:
>>> ] 
>>> ] 4. Proposed IPv6 Extension Header format
>>> ] 
>>> ]  This document proposes that all IPv6 extension headers be encoded in
>>> ]  a consistent TLV format so that it is possible for nodes to skip over
>>> ]  unknown extension headers and continue to further process the header
>>> ]  chain.
>>>
>>> But I don't see the equivalent of Section 4.2 of RFC 2460, specifying
>>> the TLV format.
>> The T is the "Next Header", the L is the "Hdr Ext Len" and V is the 
>> "Header Specific Data" as specified in the figure in Section 4 of the
>> draft.
> 
>    Well, of course "Next Header" _isn't_ the Type of this option (rather
> it's the Type of the next option).
> 
>    And the "Hdr Ext Len" isn't a particularly intuitive coding of Length
> either...

Yep. You are right on both counts, but I am not sure how we can change 
this. We cannot chain the headers without the T being in the *previous* 
header. I think the best we can do is to refrain from calling this TLV 
like you said.

> 
>    IMHO, referring to this format as "TLV" is unnecessarily confusing.

OK.

> 
>    Also IMHO, if we do define another Extension Header, it's likely we'll
> want to make it expandable using the TLV format we _are_ familiar with.

Do you mean inside the Header Specific data? If so, yes, that makes 
perfect sense.

Thanks
Suresh