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Re: [Anima] Use of LLDP in draft-richardson-anima-ipv6-lldp

Michael Richardson <mcr+ietf@sandelman.ca> Mon, 27 April 2020 19:02 UTC

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From: Michael Richardson <mcr+ietf@sandelman.ca>
To: "anima@ietf.org" <anima@ietf.org>, ieee-ietf-coord@ietf.org
cc: "Rob Wilton (rwilton)" <rwilton@cisco.com>, paul.congdon@tallac.com
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Subject: Re: [Anima] Use of LLDP in draft-richardson-anima-ipv6-lldp
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Thank you for the comments on draft-richardson-anima-ipv6-lldp.

I include them below completely, and I'll reply to this message and address
the points inline in a couple of emails.

Rob Wilton \(rwilton\) <rwilton=40cisco.com@dmarc.ietf.org> wrote:
    > Paul Congdon (Chair of IEEE 802.1 Maintenance Task Group, and very
    > familiar with LLDP) has reviewed and provided comments as an
    > individual.

    > His opinion is that this would be a serious misuse of the LLDP protocol
    > and cause problems for implementations.  The general expectation and
    > design of LLDP is that the information contained in the PDUs is fairly
    > static in nature and does not change frequently.  Assuming the IPv6
    > packets are intending to implement their own protocol and will be
    > changing frequently, encapsulating an IPv6 packet inside an LLDP TLV
    > would signal a change on each transmission and possibly cause an SNMP
    > TRAP on each packet received by a traditional implementation.

Russ Housley <housley@vigilsec.com> also forwarded Paul's comments directly
to me:

Paul Congdon <paul.congdon@tallac.com> wrote:
> I've had a brief look at this draft.   My personal belief is that this is a
> gross miss-use of the LLDP protocol.  LLDP is NOT a general L2 transport
> protocol.   It is intended to exchange a 'relatively' static local database
> with neighbors.   When an LLDP agent receives a frame, it is supposed to
> compare what it received with what it received the last time and if
> anything is different, it will throw away all of the previous information,
> replace the database with the most recently received information and
> 'wake-up' the higher layers to process the changes.  The expectation (and
> design center for the protocol) is that things do NOT change frequently.
> Assuming the IPv6 packets are intending to implement their own protocol and
> will be changing frequently, encapsulating an IPv6 packet inside an LLDP
> TLV would signal a change on each transmission and possibly cause an SNMP
> TRAP on each packet received by a traditional implementation.   If I
> understand the use case correctly, the draft is seriously miss-using the
> protocol and I believe others within 802.1 would agree with me.


    rob> I basically support Paul's comments here - I don't think that we should
    rob> be trying to tunnel IPv6 traffic over LLDP.



    rob> [As an individual] Would it be possible to carry some static
    rob> information in LLDP that could be used to setup the autonomic control
    rob> plane outside of LLDP?  This would presumably require bridges to have
    rob> some minimal support for a native IPv6 host stack.  The issue of not
    rob> forwarding IPv6 packets for an interface in L2 mode could potentially
    rob> be mitigated by targeting the IPv6 packets to the peer interface MAC
    rob> address, or possibly use the "Nearest Bridge group multicast MAC
    rob> address" (i.e. 01-80-C2-00-00-0E)?





--
Michael Richardson <mcr+IETF@sandelman.ca>, Sandelman Software Works
 -= IPv6 IoT consulting =-

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