Drops in Core

Sat Aug 15 17:31:56 UTC 2015

Is there a paper or a presentation that discusses the drops in the core?

If i were to break the total path into three legs -- the first, middle and
the last, then are you saying that the probability of packet loss is
perhaps 1/3 in each leg (because the packet passes through different IXes).
That sounds too aggressive for the middle mile. Dont you think so?

On Sat, Aug 15, 2015 at 10:51 PM, Owen DeLong <owen at delong.com> wrote:

> 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/>
> >>
>
>