Subject: mboned: AMT Open Issues

From: Tom Pusateri <[email-masked]>
Date: Thu, 04 May 2006 18:30:20 -0400

1. Currently, the AMT Relay Advertisement response to an AMT Discovery
   would use the AMT Relay anycast address as the source address to
   get the packet back through a NAT.

   The IPv6 addressing architecture document [RFC 2373] currently
   discourages using an anycast address as a source address. It says
   that until more experience is gained, it restricts this use.

   I don't think this is a serious problem but I do want to make people
   aware of the fact that RFC 2373 says not to do this.

2. Combining the anycast relay prefix with gateway subnet prefix to reduce
   the number of prefixes that need allocated by IANA from 2 per
   address family to 1 per address family.

   While this is much more efficient use of the prefix, this further
   complicates the use of an anycast prefix as a source address by
   a gateway sourcing multicast data into the native multicast network
   using a relay.

3. In trying to simplify encapsulation negotiation, it was suggested
   that we use a different anycast address to find relays supporting
   GRE than relays supporting UDP.

   This works with some additional restrictions:

   If an organization advertises the AMT anycast prefix through BGP and
   both anycast addresses are within this prefix range, then when the
   Discovery is received inside the organization, it must have at least
   one relay that injects the UDP anycast address into the IGP or else
   UDP requests will get blackholed. Same for GRE.

   Otherwise, we will need to get a different anycast prefix for each
   encapsulation type for each address family.

   If we don't combine the gateway subnet prefix with the relay anycast
   prefix, we need an additional prefix for sourcing and only 1 address
   out of each anycast prefixes will be used.

   That totals (3) /16's for IPv4 and (3) /32's for IPv6.

4. Who will own AS number assigned by IANA?

   There is not any precedence I can find for a WG owning an AS number.
   We could assign it to an individual like the WG chairs but otherwise,
   I don't know how to ask IANA for this.
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From: Dino Farinacci <[email-masked]>
Date: Thu, 4 May 2006 17:19:25 -0700

>>    That totals (3) /16's for IPv4 and (3) /32's for IPv6.

    Why not ask for 3 IPv4 /24s and 3 IPv6 /64s? I think it is more flexible
    to not complicate deployment just because of address space issues. 

    Especially for IPv6 (since there so much address space) but in the 
    short-term IPv4 will only do source-from-multicast-infrastructure so just
    allocate 2 IPv4 prefixes.

Dino

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From: Tom Pusateri <[email-masked]>
Date: Thu, 04 May 2006 21:16:14 -0400

>    to not complicate deployment just because of address space issues. 

The problem that we have been trying to get around is getting the anycast
relay prefix(es) through BGP. I'm told a /24 doesn't cut it.

>    allocate 2 IPv4 prefixes.

Pekka says that we need a /32 for IPv6 to get through BGP.

Tom

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From: John Kristoff <[email-masked]>
Date: Thu, 4 May 2006 22:12:34 -0500

On Thu, 04 May 2006 21:16:14 -0400
Tom Pusateri <[email-masked]> wrote:

> The problem that we have been trying to get around is getting the
> anycast relay prefix(es) through BGP. I'm told a /24 doesn't cut it.

It should, but it depends on where in the overall address space it is
coming from.  If it's being carved out of some larger legacy class B
netblock for example, some providers may filter it.

John

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From: Marshall Eubanks <[email-masked]>
Date: Fri, 5 May 2006 00:44:49 -0400

On May 4, 2006, at 9:16 PM, Tom Pusateri wrote:

> anycast

It's rare to hear of /24 filtering now-a-days, but note that the  
smallest assigned ARIN block is
a /22, so maybe we should ask for that.

> Pekka says that we need a /32 for IPv6 to get through BGP.

If he means the usual filters, I think a /48 will suffice.

Regards
Marshall

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From: Pekka Savola <[email-masked]>
Date: Fri, 5 May 2006 08:29:31 +0300 (EEST)

>   aware of the fact that RFC 2373 says not to do this.

This is not a problem as this prohibition was removed in the latest 
incarnation of IPv6 address architecture -- RFC 4291.

...

> If he means the usual filters, I think a /48 will suffice.

/48 is not sufficient.  Quite often, this is filtered out for very 
good reasons.

There is *no* problem asking for multiple /32's.  IANA has a block set 
aside for this: 2001::/16.  There's only one assignment yet.  IANA 
should have no problem giving out 1/10,000th of that address space..

>   I don't know how to ask IANA for this.

This is a good question, maybe we could approach this via a 
"designated expert" route..

However, if this gets tricky, we could just remove the AS number. 
It's not critical for AMT.  6to4 and Teredo anycast prefixes have been 
deployed without an AS number; having AS number simplifies route 
object maintenance a lot, and doesn't make the advertisement show as 
inconsistent origin AS.

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings
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From: Dino Farinacci <[email-masked]>
Date: Thu, 4 May 2006 22:33:27 -0700

>> Pekka says that we need a /32 for IPv6 to get through BGP.

    I propose we ask the nanog mailing list to get a quick response back to
    see how the operational community feels. Cc'ing the ripe mailing list
    would get some good international coverage.

Dino

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From: Dino Farinacci <[email-masked]>
Date: Thu, 4 May 2006 22:34:54 -0700

>> netblock for example, some providers may filter it.

    So the thought is the IANA assigned prefix length is put in the Internet
    Registry and is advertised with the same prefix length with no 
    deaggregation. That would have to be stated in a BCP.

Dino

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From: Pekka Savola <[email-masked]>
Date: Fri, 5 May 2006 09:29:57 +0300 (EEST)

>    would get some good international coverage.

Similar topic has already been discussed a while ago, see e.g.,
http://www.ripe.net/ripe/maillists/archives/address-policy-wg/2006/msg00107.html

/48 just doesn't work well enough, and there's no reason not to ask 
for /32's.  Just do it.

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From: Dino Farinacci <[email-masked]>
Date: Fri, 5 May 2006 12:11:49 -0700

>> /48 just doesn't work well enough, and there's no reason not to ask 

    Sounds good. Thanks Pekka.

Dino