Re: I-D Action: draft-ietf-6man-ipv6only-flag-03.txt

Mark Smith <markzzzsmith@gmail.com> Mon, 22 October 2018 23:05 UTC

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From: Mark Smith <markzzzsmith@gmail.com>
Date: Tue, 23 Oct 2018 10:04:45 +1100
Message-ID: <CAO42Z2ws=J=Jmww=FoQiZLz=RHBakTOOxKTYS9UP87uKa7XbuA@mail.gmail.com>
Subject: Re: I-D Action: draft-ietf-6man-ipv6only-flag-03.txt
To: Tim Chown <Tim.Chown@jisc.ac.uk>
Cc: Mikael Abrahamsson <swmike@swm.pp.se>, 6man WG <ipv6@ietf.org>
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On Mon, 22 Oct 2018 at 21:00, Tim Chown <Tim.Chown@jisc.ac.uk> wrote:
>
> > On 22 Oct 2018, at 06:22, Mikael Abrahamsson <swmike@swm.pp.se> wrote:
> >
> > On Mon, 22 Oct 2018, Brian E Carpenter wrote:
> >
> >> Wait, are you saying that no switches contain ARP caches? That would
> >> truly surprise me.
> >
> > The only IPv4 state that an L2 switch might contain for purpose of forwarding packets is if that switch implements SAVI like functionality.
> >
> > The L2 switch doesn't need an ARP cache to perform its basic function. I have plenty of stupid L2 switches here in my household that doesn't have a management interface and doesn't understand IP at all. They only do ethernet header functions.
>
> There may be some examples where there are "helpers" supported, such as IGMP snooping, to store state about observed multicast sources, but those are more likely in enterprise deployments than home networks.
>

I don't have experience with them (been in carrier/ISP land for a
quite a while) or knowledge of how widely it is used, however
enterprise Wifi APs look to be performing ARP caching to reduce
link-layer broadcast traffic, which is IPv4 state being maintained in
a layer 2 device. e.g.

https://www.cisco.com/web/techdoc/wireless/access_points/online_help/eag/123-04.JA/1100/h_ap_services_arp.html

I think David Farmer might have mentioned it being used some time here
in the past.


Regards,
Mark.


> Tim
>
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