Subject: Re: ipv6 anycast

From: Mikael Abrahamsson <[email-masked]>
Date: Wed, 1 Sep 2010 09:20:56 +0200 (CEST)

On Wed, 1 Sep 2010, Randy Bush wrote:

> anyone have pointers to production operational use of ipv6 anycast on
> the real interwebz?

I've been confused before, so I just have to ask. Do you mean the BGP kind 
of Anycast, or the IPv6 Anycast spoken about in here: 
http://www.iana.org/assignments/ipv6-anycast-addresses/ ?

I think it's very unfortunate that there are two concepts sharing the 
same name. I saw someone asking on a Linux list about this, and before 
everybody figured out what he wanted there was some confusion...

-- 
Mikael Abrahamsson    email: [email-masked]

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From: Randy Bush <[email-masked]>
Date: Wed, 01 Sep 2010 16:43:50 +0900

> http://www.iana.org/assignments/ipv6-anycast-addresses/ ?

the ipv6 new invention.

randy

---

From: Tina TSOU <[email-masked]>
Date: Wed, 01 Sep 2010 15:57:48 +0800

B. R.
Tina
http://tinatsou.weebly.com/index.html
----- Original Message ----- 
From: "Randy Bush" <[email-masked]>
To: "Mikael Abrahamsson" <[email-masked]>
Cc: "IPv6 v6ops" <[email-masked]>
Sent: Wednesday, September 01, 2010 3:43 PM
Subject: Re: ipv6 anycast

>> http://www.iana.org/assignments/ipv6-anycast-addresses/ ?
People used IPv4 anycast in 6to4 and 6rd nowadays. Who knows that people may 
use IPv6 anycast in the future? (Randy, here are you Q-tips;-)

---

From: Jeroen Massar <[email-masked]>
Date: Wed, 01 Sep 2010 10:08:34 +0200

>> http://www.iana.org/assignments/ipv6-anycast-addresses/ ?

As that list states there effectively is only mobility & subnet-anycast.

I have never seen anybody use mobility except for a test setup and
subnet-anycast, I actually don't know the reason for existence...
Well, there is one of course, that if you ping it you know which nodes
are configured to use that prefix, which is only useful if you have
multiple prefix on the same link.

"Production operational" use == 0 though on my score card.

Greets,
 Jeroen

---

From: Randy Bush <[email-masked]>
Date: Wed, 01 Sep 2010 17:15:05 +0900

> People used IPv4 anycast in 6to4 and 6rd nowadays.

which has nothing to do with my question.  been using ipv4 style anycast
for a decade and a half.  i have too much operatonal experience with it.

> Who knows that people may use IPv6 anycast in the future? (Randy, here
> are you Q-tips;-)

if i could predict the future, i would bet on the horses not hack on
routers and computers.  if you can do better, why are you wasing your
time here?

but again, this has nothing to do with what i asked.  deploy q-tips, and
i will try again.

>> anyone have pointers to production operational use of ipv6 anycast on

that speaks to the present and past tense.  i am not interested in what
might happen.  i am interested in real operational experience with ipv6
(not ipv4-style) anycast on the real interwebz.

randy

---

From: Randy Bush <[email-masked]>
Date: Wed, 01 Sep 2010 18:32:57 +0900

> So practically there's only a single anycast concept now in IPv6 as 
> well.

then explain why there is reservation for an anycast address on a subnet
link?

randy

---

From: Pekka Savola <[email-masked]>
Date: Wed, 1 Sep 2010 12:29:27 +0300 (EEST)

On Wed, 1 Sep 2010, Mikael Abrahamsson wrote:
>>  anyone have pointers to production operational use of ipv6 anycast
>>  on the real interwebz?
>
> I've been confused before, so I just have to ask. Do you mean the BGP kind of 
> Anycast, or the IPv6 Anycast spoken about in here: 

This distinction is less relevant today because since RFC4291, it's 
allowed to use ipv6 anycast address as a source address.  From the 
RFC:

     o The restrictions on using IPv6 anycast addresses were removed
       because there is now sufficient experience with the use of anycast
       addresses, the issues are not specific to IPv6, and the GROW
       working group is working in this area.

Special thanks to Joe Abley who pushed this through.

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings

---

From: Pekka Savola <[email-masked]>
Date: Wed, 1 Sep 2010 12:39:35 +0300 (EEST)

> then explain why there is reservation for an anycast address on a subnet

On a link which typically includes 2^64 addresses, it probably doesn't 
hurt to reserve some if someone or a protocol would like to use it for 
anycast purposes (in the similar fashion it's used today with v4, just 
without requiring manual assignment).

But as I mentioned on 6man list in the context of /127 and RFC3627, I 
wouldn't personally object to obsoleting RFC2526.

---

From: Randy Bush <[email-masked]>
Date: Wed, 01 Sep 2010 18:41:52 +0900

> wouldn't personally object to obsoleting RFC2526.

might be prudent to know if anyone is actually using it in operation on
the net first.

randy

---

From: Ole Troan <[email-masked]>
Date: Wed, 1 Sep 2010 11:46:25 +0200

> might be prudent to know if anyone is actually using it in operation on

I use them for my network. RFC5969.

cheers,
Ole

---

From: Randy Bush <[email-masked]>
Date: Wed, 01 Sep 2010 18:52:38 +0900

> I use them for my network. RFC5969.

aha!  do you mean

5.  Troubleshooting and Traceability
   ...
   The 6rd CE and BR SHOULD support the IPv6 Subnet-Router anycast
   address [RFC4291] for its own 6rd delegated prefix.  This allows, for
   example, IPv6 ICMP echo messages to be sent to the 6rd virtual
   interface itself for additional troubleshooting of the internal
   operation of 6rd at a given CE or BR.

randy

---

From: Ole Troan <[email-masked]>
Date: Wed, 1 Sep 2010 11:55:14 +0200

>   operation of 6rd at a given CE or BR.

indeed. and note that this makes no requirement that _any_ type of interface has to support this.

cheers,
Ole

---

From: Mark Smith <[email-masked]>
Date: Wed, 1 Sep 2010 19:25:27 +0930

On Wed, 01 Sep 2010 15:50:41 +0900

> anyone have pointers to production operational use of ipv6 anycast on

Few operators seem to hang around here (sadly), I'd suggest the ipv6-ops
mailing list would be a better place to ask.

---

From: [email-masked]
Date: Wed, 01 Sep 2010 11:58:24 +0200 (CEST)

> everybody figured out what he wanted there was some confusion...

It is indeed extremely unfortunate. Especially so since IPv4 anycast is
widely used, and exactly the same technical solution works just fine for
IPv6 also. The so called "IPv6 anycast" as defined in the IPv6 protocol
standards has, as far as we know, zero usage.

Steinar Haug, Nethelp consulting, [email-masked]

---

From: Mark Smith <[email-masked]>
Date: Wed, 1 Sep 2010 21:40:39 +0930

On Wed, 1 Sep 2010 11:55:14 +0200

> indeed. and note that this makes no requirement that _any_ type of interface has to support this.

Why did you need to clarify that?

Isn't a "6rd virtual interface" an interface?

---

From: Ole Troan <[email-masked]>
Date: Wed, 1 Sep 2010 15:35:08 +0200

> Isn't a "6rd virtual interface" an interface?

it should read "any other type of..."

cheers,
Ole

---

From: Randy Bush <[email-masked]>
Date: Wed, 01 Sep 2010 22:48:36 +0900

> interface has to support this.

btw, that is an rfc, not a network :)

do you know if free.fr and/or others actually deployed and tested this?
among other things, i worry about code paths that are rarely, if ever,
used.

randy

---

From: Ole Troan <[email-masked]>
Date: Wed, 1 Sep 2010 16:17:36 +0200

> btw, that is an rfc, not a network :)

that's why I said my network (as in at home), which even I have to admit isn't very large. ;-)
> among other things, i worry about code paths that are rarely, if ever,

I have tested it (and yes, it was broken the first time I tried). IPv6 anycast is exactly like IPv4 anycast though, so
the 'anycast' code path isn't very large. the only difference is with how ND is done (not an issue on this link), and the source address selection (pick a unicast address as source instead of anycast).

cheers,
Ole

---

From: Randy Bush <[email-masked]>
Date: Wed, 01 Sep 2010 23:21:55 +0900

> IPv6 anycast is exactly like IPv4 anycast

excuse?  ipv4 anycast, as it is used, injects a route into the control
plane.

randy

---

From: Ole Troan <[email-masked]>
Date: Wed, 1 Sep 2010 16:24:41 +0200

> excuse?  ipv4 anycast, as it is used, injects a route into the control

right, so IPv4 supports an anycast address existing anywhere in the network apart from two nodes with the same anycast address on the same link. IPv6 removes that restriction.

cheers,
Ole

---

From: Mark Smith <[email-masked]>
Date: Thu, 2 Sep 2010 06:49:46 +0930

On Wed, 01 Sep 2010 22:48:36 +0900

> among other things, i worry about code paths that are rarely, if ever,

Here is a post of somebody who used it to provide "poor mans" HSRP.

http://lists.cluenet.de/pipermail/ipv6-ops/2010-June/003639.html

---

From: Mark Smith <[email-masked]>
Date: Thu, 2 Sep 2010 08:18:04 +0930

On Wed, 01 Sep 2010 21:58:40 +0000 (GMT)
Michael Smith <[email-masked]> wrote:

> 
> 
> On Sep 01, 2010, at 02:53 PM, Mark Smith <[email-masked]> wrote:
> 
> That's how I use it on GSR's that will never have HSRPv6 support in 12.0S.  It works pretty well, although the failover time is +/- 30 seconds.
> 

Which isn't any worse than traditional spanning tree (not that that is
great these days, but it's better than nothing, and seems to still be
used a fair bit).

Another possibility would be to provide last hop redundancy for an
application on a single LAN segment, where the host people aren't
trusted to inject routes into the network by the routing people e.g.
colo scenarios, or where the network and the hosts are operated by
separate organisations with separate SLAs. Recovery time isn't as good
as HSRP/VRRP etc. obviously, but its better than nothing, and should be
commonly available as baseline IPv6 functionality, unlike IPv4 which
doesn't have a "within prefix anycast" mechanism at all.

It could possibly be used for multiple NTP servers on a LAN
segment instead of multicast. 30 second recovery from failure wouldn't
be an issue (IIRC, NTP only issues time queries once every 60 seconds
or so once the local clock has converged, and of course the local clock
keeps ticking even if the NTP server goes away), and it would avoid
periodic multicast NTP queries from the clients being flooded through
the segment.

Regards,
Mark.