On Mar 11, 2012, at 3:15 PM, Iljitsch van Beijnum wrote:

> On 11 Mar 2012, at 20:15 , Joel jaeggli wrote:
> 
>>> The IETF and IRTF have looked at the routing scalability issue for a
>>> long time. The IETF came up with shim6, which allows multihoming
>>> without BGP. Unfortunately, ARIN started to allow IPv6 PI just in
>>> time so nobody bothered to adopt shim6.
> 
>> That's a fairly simplistic version of why shim6 failed. A better reason
>> (appart from the fact the building an upper layer overlay of the whole
>> internet on an ip protocol that's largely unedeployed was hard) is that
>> it leaves the destination unable to perform traffic engineering.
> 
> I'm not saying that shim6 would have otherwise ruled the world by now, it was 
> always an uphill battle because it requires support on both sides of a 
> communication session/association.
> 
> But ARIN's action meant it never had a chance. I really don't get why they 
> felt the need to start allowing IPv6 PI after a decade, just when the 
> multi6/shim6 effort started to get going but before the work was complete 
> enough to judge whether it would be good enough.
> 
>> That fundementaly is the business we're in when advertising prefixes to more
>> than one provider, ingress path selection.
> 
> That's the business network operators are in. That's not the business end 
> users who don't want to depend on a single ISP are in. Remember, shim6 was 
> always meant as a solution that addresses the needs of a potential 1 billion 
> "basement multihomers" with maybe ADSL + cable. The current 25k or so 
> multihomers are irrelevant from the perspective of routing scalability. It's 
> the other 999,975,000 that will kill the routing tables if multihoming 
> becomes mainstream.


When discussing 'why shim6 failed' I think its only fair to include a link to a 
(well reasoned, imho) network operator's perspective on what it did and did not 
provide in the way of capabilities that network operators desired.

http://www.nanog.org/meetings/nanog35/abstracts.php?pt=NDQ3Jm5hbm9nMzU=&nm=nanog35

-Darrel

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