Drops in Core

Sat Aug 15 17:21:34 UTC 2015

I would say that the probability of a packet drop at any particular peering
point is less than the probability at one of the two edges.

However, given that most packets are likely to traverse multiple peering
points between the two edges, the probability of a packet drop along
the way at one of the several peering points overall is roughly equal
to the probability of a drop at one of the two edges.

YMMV.

Owen

> On Aug 15, 2015, at 10:07 , Glen Kent <glen.kent at gmail.com> wrote:
> 
> Hi Bill,
> 
> Just making sure that i get your point:
> 
> Youre saying that the probability of packet drop at peering points would
> roughly match that at the edge. Is it? I thought that most core switches
> have minimal buffering and really do cut-through forwarding. The idea is
> that the traffic that they receive is already shaped by the upstream
> routers.
> 
> Glen
> 
> 
> 
> On Sat, Aug 15, 2015 at 10:33 PM, William Herrin <bill at herrin.us> wrote:
> 
>> On Sat, Aug 15, 2015 at 12:47 PM, Glen Kent <glen.kent at gmail.com> wrote:
>>> Is it fair to say that most traffic drops happen in the access layers, or
>>> the first and the last miles, and the % of packet drops in the core are
>>> minimal? So, if the packet has made it past the first mile and has
>>> "entered" the core then chances are high that the packet will safely get
>>> across till the exit in the core.
>> 
>> Hi Glen,
>> 
>> I would expect congestion loss at enough peering points (center of the
>> core) to put it in the same league as noisy cable at the edge.
>> 
>> Regards,
>> Bill Herrin
>> 
>> 
>> 
>> --
>> William Herrin ................ herrin at dirtside.com  bill at herrin.us
>> Owner, Dirtside Systems ......... Web: <http://www.dirtside.com/>
>> 