Re: [homenet] dst/src routing drafts (for IETF-91 rtgwg)

Ray Hunter <> Wed, 29 October 2014 12:05 UTC

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Date: Wed, 29 Oct 2014 13:05:01 +0100
From: Ray Hunter <>
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Cc: Ole Troan <>, "" <>, "" <>, Mikael Abrahamsson <>, David Lamparter <>
Subject: Re: [homenet] dst/src routing drafts (for IETF-91 rtgwg)
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Fred Baker (fred) wrote:
> On Oct 28, 2014, at 11:28 PM, David Lamparter<>  wrote:
>> What I'm personally wondering most in this regard is: to what extent
>> will larger networks deploy multiple prefixes to the hosts?
> Well, define “larger”. Any network that gets a PI prefix is unlikely to deploy multiple prefixes. The question is at what size network is makes sense to obtain an AS number and a PI prefix, and use BGP to talk with one’s upstream.
I don't agree with this statement for the following reasons.

Availability: There are many enterprises that have very numerous 
far-flung sales-office type locations which do not host any critical 
data or applications, but which could benefit from higher availability 
than that provided by a single ISP provider (some of which are currently 
served by a specialised box offering a Very Small Office Service running 
dual IPSec tunnels to a central site, which then performs the break out 
to the corporate intranet/Internet)

Latency: There are many sites which could benefit from local Internet 
breakout to regional cloud services, where you don't want to suffer the 
latency associated with a back haul from an office in Australia to a 
regional hub in Hong Kong, or even East coast US to West coast US and 
back. You'd still also want some back up via the central breakout if the 
local breakout failed.

Cost: There are cost savings to be made in many countries where private 
network services are still many orders of magnitude more expensive than 
plain old Internet. So Internet offload for non-mission-critical traffic 
can be very attractive. If you could achieve this via direct host-server 
connections using address selection rules or multipath TCP; rather than 
via PBR, GRE tunnels + NAT, that would be a lot simpler.

>   Wherever that boundary is, below that networks will use PA prefixes. The question then becomes: will they multi home?
> And I think the answer today is that we don’t know the answer.
This I agree with.