The updates in a BGPSEC island can be BGPSEC (i.e., signed) or BGP-4 (i.e.,
unsigned).
In either case, the update necessarily has AS-path info.
If the update is BGP-4 (i.e., unsigned), it has the BGP-4 AS_PATH (mandatory)
in it.
If the update is BGPSEC (i.e., signed), then it MUST have the "Secure Path" in
it.
The Secure Path is in the form of {ASN1, pCount1, ASN2, pCount2, ...., ASN-k,
pCount-k}.
Please refer to slide 8 in Matt's presentation (BGPSEC Protocol) in Paris.
The Secure Path is semantically equivalent to the BGP-4 AS_PATH.
When the update is to leave a BGPSEC island to go to a BGP-4 only AS,
then the Secure Path is easily converted to BGP-4 AS_PATH at the edge of the
BGPSEC island.
Any prepend ASN that was collapsed in BGPSEC will be repeated pCount number of
times,
and any transparent route server ASN (with pCount=0) in BGPSEC will be removed.
Is this semantic equivalence (of the Secure Path) and
the guarantee of convertibility to BGP-4 AS_PATH not enough?
Should we really require in BGPSEC that the BGP-4 AS_PATH be carried (in a
pristine way)
in addition to the Secure Path, albeit at the cost of duplication and
associated
processing cost/confusion? Just a honest question seeking people's opinion.
Sriram
>-----Original Message-----
>From: sidr-boun...@ietf.org [mailto:sidr-boun...@ietf.org] On Behalf Of Robert
>Raszuk
>Sent: Monday, April 09, 2012 3:19 AM
>To: sidr@ietf.org
>Cc: i...@ietf.org List
>Subject: Re: [sidr] draft-ietf-sidr-bgpsec-threats-02: Path shortening &
>lengthening
>
>
>> Your analysis assumes that there a conventional BGP-4 AS_PATH field
>> and then there is is BGPSEC_Path_Signatures from which AS path info
>> can be inferred separately. This is not true in the latest BGPSEC
>> update format as Matt presented it in Paris.
>
>How an optional attribute replace well-known mandatory one ?
>
>Sorry but for such step formal IDR WG approval is necessary if you choose to
>propose BGPSEC_Path_Signatures as mandatory attribute. This is major BGP
>protocol change.
>
>Documentation of partial deployment is required as well as two interoperable
>implementations ;).
>
>RFC4271:
>
>5.1.2. AS_PATH
>
> AS_PATH is a well-known mandatory attribute. This attribute
> identifies the autonomous systems through which routing information
> carried in this UPDATE message has passed. The components of this
> list can be AS_SETs or AS_SEQUENCEs.
>
>
>draft-ietf-sidr-bgpsec-protocol-02.txt
>
> This document specifies a new optional (non-transitive) BGP path
> attribute, BGPSEC_Path_Signatures.
>
>
>Best regards,
>R.
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