Subject: [alto] Highly volatile network partitioning

From: Enrico Marocco <[email-masked]>
Date: Tue, 13 Oct 2009 15:52:13 +0200

Hi all,

as I happened to discover recently, in at least two cases of fairly big
ISPs IP addresses dynamically assigned to residential users are taken
from pools regardless of the subscriber contracts. As a consequence, in
such scenarios the same address could be quickly reassigned to users
that, despite being topologically close, have very different provisioned
bandwidth. So, while such reassignments are unlikely to happen to the
peers participating in a swarm -- or at least are not going to have a
significant statistical impact -- I can't figure any easy way to keep
such information updated in relatively static maps some of the proposed
solutions use (I can see how static maps AND dynamic queries can be used
together though).

Now, we had several discussions about the usefulness of information
regarding provisioned bandwidth in peer selection without reaching
consensus, and honestly don't know how common such an address assignment
policy is. Thus I would be very interested in hearing what people think
about that, whether it should be something reflected in the requirements
and addressed by the solution, or simply just ignored.

-- 
Ciao,
Enrico

---

From: Reinaldo Penno <[email-masked]>
Date: Tue, 13 Oct 2009 14:05:21 -0400

I'm aware of this issue but IMO this is not a specific ALTO issue and
therefore I do not think we should try to solve it. This is an ISP
Policy/Provisioning issue.

The fast reuse of IP addresses have other impacts such as security,
accounting, subscriber limits, etc. The ISPs today are aware of this issue
since they are using or (trying to move) to a 'sticky' IP address approach
where the same device gets always the same address and/or make sure it takes
a 'safe' long time to recycle the same IP address to another customer.

One could also argue that if the ISP is running the ALTO Service (or in
partnership with a Content Provider) it is in its best interest to
invalidate any IP/customer associated info whenever an IP address is dished
out by the DHCP/Radius Server. But again, I think this is a generic
provisioning problem ISPs face day to day.

Thanks,

Reinaldo

---

From: sy ding <[email-masked]>
Date: Wed, 14 Oct 2009 16:23:00 +0800

As  I know, it is common that one ip address can have different
bandwidth due to dynamic assignment in reality. So I am afraid the
cost of providing accurate bandwidth information just by address would
be a little bit high. However this doesn't mean providing the location
map has no sense for traffic optimization . Anyway, we hope the
traffic can be localized as much as possible.

Best regards
Syon DIng

2009/10/14 Reinaldo Penno <[email-masked]>:
> _______________________________________________
> alto mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/alto
>

---

From: Enrico Marocco <[email-masked]>
Date: Wed, 14 Oct 2009 12:06:53 +0200

> provisioning problem ISPs face day to day.

I agree, it is a general problem that boils down to the scarcity of IP
addresses and to fact that CIDR blocks are usually reassigned to users
either on a topological basis or on a subscription basis, but generally
not both. I can think of a provisioning policy that could preserve
network partitioning both on a topological level and on a provisioned
bandwidth level (i.e. topology based partitioning and subsequent
sub-partitioning on a contract basis, e.g. first X% addresses in each
partition assigned to contract A subscribers, Y% to contract Bs, and so
on), but I don't know how common they are today and am wondering whether
ALTO would provide enough incentive for ISPs to switch to them.
Especially because applications only, not ISPs, might (am still not sure
if they actually will) directly benefit from the use of provisioned
bandwidth information in peer selection.

-- 
Ciao,
Enrico

---

From: "Woundy, Richard" <[email-masked]>
Date: Wed, 14 Oct 2009 14:47:40 -0400

not both.

The address assignment approach by an ISP may depend on the last mile
network topology.

For a last mile shared media network like cable, it is typical to assign
addresses based on network topology, not based on subscription. It may
be different for a last mile point to point network, I don't know.

>I don't know how common they are today and am wondering whether ALTO
would provide enough incentive for ISPs to switch to them.
>Especially because applications only, not ISPs, might (am still not
sure if they actually will) directly benefit from the use of provisioned
bandwidth information in peer selection.

I suspect that this incentive would not be sufficient, at least in many
cases. The ISP's address assignment policies are usually driven by IPv4
address conservation, rather than application optimization.

The regional Internet registries typically expect 80% utilization of
addresses, before they grant additional IP address space to the ISP. For
example, https://www.arin.net/policy/nrpm.html#four24.

Application optimization is great, but you can't operate a growing ISP
without a growing pool of IP addresses. :)

-- Rich

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of
Enrico Marocco
Sent: Wednesday, October 14, 2009 6:07 AM
To: Reinaldo Penno
Cc: [email-masked]
Subject: Re: [alto] Highly volatile network partitioning

Reinaldo Penno wrote:
> accounting, subscriber limits, etc. The ISPs today are aware of this 
> issue since they are using or (trying to move) to a 'sticky' IP 
> address approach where the same device gets always the same address 
> and/or make sure it takes a 'safe' long time to recycle the same IP
address to another customer.
> 
> One could also argue that if the ISP is running the ALTO Service (or 
> in partnership with a Content Provider) it is in its best interest to 
> invalidate any IP/customer associated info whenever an IP address is 
> dished out by the DHCP/Radius Server. But again, I think this is a 
> generic provisioning problem ISPs face day to day.

--
Ciao,
Enrico