Can P2P applications learn to play fair on networks?

Mon Oct 22 17:35:23 UTC 2007

Bora Akyol wrote:
> 1) Legal Liability due to the content being swapped. This is not a technical
> matter IMHO.

Instead of sending an icmp host unreachable, they are closing the connection via 
spoofing. I think it's kinder than just dropping the packets all together.

> 2) The breakdown of network engineering assumptions that are made when
> network operators are designing networks.
> 
> I think network operators that are using boxes like the Sandvine box are
> doing this due to (2). This is because P2P traffic hits them where it hurts,
> aka the pocketbook. I am sure there are some altruistic network operators
> out there, but I would be sincerely surprised if anyone else was concerned
> about "fairness"
> 

As has been pointed out a few times, there are issues with CMTS systems, 
including maximum upstream bandwidth allotted versus maximum downstream 
bandwidth. I agree that there is an engineering problem, but it is not on the 
part of network operators. DSL fits in it's own little world, but until VDSL2 
was designed, there were hard caps set to down speed versus up speed. This has 
been how many last mile systems were designed, even in shared bandwidth mediums. 
More downstream capacity will be needed than upstream. As traffic patterns have 
changed, the equipment and the standards it is built upon have become antiquated.

As a tactical response, many companies do not support the operation of servers 
for last mile, which has been defined to include p2p seeding. This is their 
right, and it allows them to protect the precious upstream bandwidth until 
technology can adapt to a high capacity upstream as well as downstream for the 
last mile.

Currently I show an average 2.5:1-4:1 ratio at each of my pops. Luckily, I run a 
DSL network. I waste a lot of upstream bandwidth on my backbone. Most 
downstream/upstream ratios I see on last mile standards and equipment derived 
from such standards isn't even close to 4:1. I'd expect such ratio's if I 
filtered out the p2p traffic on my network. If I ran a shared bandwidth last 
mile system, I'd definitely be filtering unless my overall customer base was 
small enough to not care about maximums on the CMTS.

Fixed downstream/upstream ratios must die in all standards and implementations. 
It seems a few newer CMTS are moving that direction (though I note one I quickly 
found mentions it's flexible ratio as beyond DOCSIS 3.0 features which implies 
the standard is still fixed ratio), but I suspect it will be years before 
networks can adapt.

Jack Bates