Re: [netext] I-D Action: draft-ietf-netext-logical-interface-support-03.txt

Sri Gundavelli <> Wed, 07 September 2011 04:08 UTC

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Date: Tue, 06 Sep 2011 21:09:54 -0700
From: Sri Gundavelli <>
To: Brian Haley <>
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Thread-Topic: I-D Action: draft-ietf-netext-logical-interface-support-03.txt
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Subject: Re: [netext] I-D Action: draft-ietf-netext-logical-interface-support-03.txt
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Hi Brian,

Long time :)

Thanks for the review comment. Please see inline.

On 9/6/11 6:36 AM, "Brian Haley" <> wrote:

> Hi Sri,

> I read this draft and had a comment on Section 6.5:
> 6.5.  ND Considerations for Logical Interface
>    The following are the Neighbor Discovery related considerations for
>    the logical interface.
>    o  Any Neighbor Discovery messages, such as Router Solicitation,
>       Neighbor Solicitation messages that the host sends to a multicast
>       destination address of link-local scope such as, all-nodes, all-
>       routers, solicited-node multicast group addresses, using either an
>       unspecified (::) source address, or a link-local address
>       configured on the logical interface will be replicated and
>       forwarded on each of the sub-interfaces under that logical
>       interface.  However, if the destination address is a unicast
>       address and if that target is known to exist on a specific sub-
>       interface, the message will be forwarded only on that specific
>       sub-interface.
> I'm not sure about other OSes, but since you mentioned the Linux bonding
> driver
> as an example of a Logical interface I can respond regarding that.  There are
> configurations where you do NOT want to replicate a packet and forward it on
> all
> the underlying physical interfaces.  Doing so can cause DAD failures if any of
> the other interfaces see those packets sent to the all-nodes multicast
> address.
>  We noticed and fixed that back in 2008.

Thanks for the info. I'm not sure, if your failure scenario is specific to
logical interface construct, or if you are referring to a general case of
packet replication. For the case of logical interface construct,
essentially, we are presenting a single interface to the host stack, but
underneath there are multiple physical interfaces. Some of the operations
such as router discovery when initiated on the logical interface, should
translate to performing this operation on multiple physical interfaces.

For example, Sending a RS message on a LI abstracting WLAN and WiMAX should
result in sending that RS message on both the paths. I'm sure, this can be
achieved in multiple ways, but the external behavior what needs to be seen
is the generation of two RS packets on those two sub-interfaces. May be if
you can provide more info on your failure case, we can structure this right.
But, that was our intent.

> BTW, I'm not subscribed to net-next, so haven't seen any previous discussion
> on
> the draft.

Will surely help us, if you are on the list.