Subject: [alto] New draft submitted...

From: Nicholas Weaver <[email-masked]>
Date: Wed, 4 Mar 2009 07:37:29 -0800

http://www.ietf.org/internet-drafts/draft-weaver-alto-edge-caches-00.txt

I just submitted a new draft on why I think P2P edge caches are  
necessary, and how localization interacts with edge-caches.

Among other things, edge-cache support requires associating filename  
information with requests (and therefore has privacy implications), etc.

Abstract:
    Without caches in the infrastructure, peer to peer content  
delivery's
    primary effect is cost shifting rather than cost savings.  Even with
    perfect localization, depending on the relative cost of last-mile
    uplink bandwidth verses transport bandwidth, P2P may substantially
    increase aggregate cost.  Yet the addition of edge caches, caches
    located in the ISPs near the customers, radically change the
    economics of P2P content delivery.  Edge caches interact very
    strongly with localization services for P2P content delivery, and  
any
    localization service must be tightly integrated into edge-cache
    operation.

Comments greatly appreciated.

---

From: Arnaud Legout <[email-masked]>
Date: Tue, 10 Mar 2009 18:16:02 +0100

Hi,

I believe that using caches (using regular clients on dedicated well 
placed machine) makes sense to
reduce last miles traffic.

However, I do not see a scenario in which caches are useful (here I mean 
that they cannot be replaced by
a real P2P client with an appropriate locality definition used by the 
P2P protocol because the ISP architecture
prevent real P2P clients to be located at an appropriate location) 
without requiring a large number of such caches.

In particular, deploying such caches can be much more expensive that 
what you present.
If you take for instance the case of a DSL provider, you need to place 
one dedicated cache per DSLAM.
As there is a lot of DSLAM for a single ISP (hundreds to thousands) the 
cost is not negligible.
One may argue that even a few millions of dollars is not significant for 
an ISP, but if it is to reduce a cost shift
from content providers to network providers, it might be hard to 
convince ISPs that it is up to them to invest
in a new infrastructure.

Do you have in mind specific scenarios in which few caches can save a lot
of last mile traffic, or did I misunderstood your proposition.

Regards,
Arnaud.

Nicholas Weaver wrote:
>    Without caches in the infrastructure, peer to peer content delivery's
>    strongly with localization services for P2P content delivery, and any
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> alto mailing list
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-- 
Arnaud Legout, Ph.D.

INRIA Sophia Antipolis - Planète  Phone : 00.33.4.92.38.78.15
2004 route des lucioles - BP 93   Fax   : 00.33.4.92.38.79.78
06902 Sophia Antipolis CEDEX      E-mail: [email-masked]
FRANCE                            Web   : http://www-sop.inria.fr/planete/Arnaud.Legout/index.html

---

From: Nicholas Weaver <[email-masked]>
Date: Tue, 10 Mar 2009 10:22:52 -0700

On Mar 10, 2009, at 10:16 AM, Arnaud Legout wrote:

> However, I do not see a scenario in which caches are useful (here I  
> mean that they cannot be replaced by
> a real P2P client with an appropriate locality definition used by  
> the P2P protocol because the ISP architecture
> If you take for instance the case of a DSL provider, you need to  
> place one dedicated cache per DSLAM.
> As there is a lot of DSLAM for a single ISP (hundreds to thousands)  
> the cost is not negligible.
> One may argue that even a few millions of dollars is not significant  
> for an ISP, but if it is to reduce a cost shift

The caches don't need to be at the DSLAM, but can be "one up" from the  
DSLAM/CMTS.

THe cache savings is not on the last mile download, but the last mile  
UPLOAD which P2P requires, and it is this last-mile upload which make  
P2P especially unattractive on cable networks.

The "Second to last mile" cost of bandwidth (from the central point  
within the ISP to the DSLAM) is the only part that would be saved by  
locating the caches at the DSLAM rather than slightly more centrally  
in the ISP.

---

From: Reinaldo Penno <[email-masked]>
Date: Tue, 10 Mar 2009 10:49:20 -0700

I tend to agree. P2P content caches are not going to save on the download
from a client perspective because you have to download your file one way or
another. 

They will save on interconnection costs but I would suggest on a large
network, with multiple peering points, over time more savings would be found
on the upload from clients or intra-network (metro/regional) transfer of
data (which indirectly save on interconnection costs).

BTW, there has been efforts to put P2P clients in caches so that caches are
seen just as a very high speed peer. Caches then integrate seamlessly into
the P2P network. There has also been many interesting studies on P2P caches
from (long vs. short tail perspective) vs. (micro caches vs. huge caches).

Thanks,

Reaindlo