Re: [Idr] I-D Action: draft-previdi-idr-segment-routing-te-policy-07.txt

[Robert Raszuk <[e-mail]>]

Eric,

You can't withdraw something which you did not successfully parsed. So the
MP_REACH_NLRI must be parsed entirely to be able to apply the
"treat-as-withdraw" otherwise procedures 3j from RFC7606 apply.

Also I do not see any definition and levels of "mangled" in RFC7606 :)

Thx,
R.

On Mon, Oct 9, 2017 at 10:16 PM, Eric C Rosen <[e-mail]> wrote:

> On 10/6/2017 10:38 AM, Nandan Saha wrote:
>
>> 5. Conflicting mandate for malformed NLRI handling.
>> In section 4.2.1 of this draft, the first bullet point's 2nd sentence is
>> <<<
>> If the NLRI is not one of the legal lengths, a router
>>       supporting this document and that imports the route MUST consider
>>       it to be malformed and MUST apply the "treat-as-withdraw" strategy
>>       of [RFC7606]
>> >>>
>> Where as the last sentence in section 4.2.1 is
>> <<<
>> A unacceptable SR Policy update that has an invalid NLRI portion MUST
>>    trigger a reset of the BGP session
>> >>>
>> Can the draft be updated to simply remove the reference to
>> treat-as-withdraw in the first statement since one cannot withdraw a NLRI
>> if one cannot parse it; and also because it conflicts with the 2nd mandate.
>>
>
> You do not want to trigger a reset of the BGP session unless the UPDATE is
> so mangled that you can't  continue to parse the TCP octet stream.
> If the UPDATE is well-formed, but the NLRI is not one of the two legal
> lengths (12 or 24), treat-as-withdraw is appropriate.
>
> Probably the sentence about triggering a reset of the BGP session can be
> omitted, since that is only necessary when the UPDATE is totally mangled,
> and in that case it is normal BGP behavior and nothing particular to do
> with the SAFI being discussed.
>
> 1. Behavior when only one of Color / Remote end point sub-tlv is present
>> in the Tunnel encap tlv.
>>   Should the match on either color or remote end point be done for
>> acceptance? For example the color sub-tlv is present, but the remote end
>> point isn't. So the color of the color sub-tlv must match the color in the
>> NLRI. Or should the condition for matching of color / remote end point be
>> done only if both color and remote end point are present.
>>
>> 2. What is the rationale for including remote end point / color sub tlvs
>> in the tunnel encap tlv.
>>   The NLRI already has the color and endpoint. Why is there an option to
>> also include a end point and color in the tunnel encap tlv and then have to
>> make sure it matches the NLRI?
>>
>
> I believe the Remote Endpoint is mandatory, according to the tunnel-encaps
> draft.  (There has been some controversy on this point though.)
> The color sub-tlv is not mandatory, but you can't really stop someone from
> including it.
>
> The purpose of these rules is to cause a policy to be rejected if it
> contains contradictory information.
>
>
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