[183142] in North American Network Operators' Group
Re: Drops in Core
daemon@ATHENA.MIT.EDU (Rafael Possamai)
Sat Aug 15 13:31:38 2015
X-Original-To: nanog@nanog.org
In-Reply-To: <CAPLq3UNEG+CNEns8Ciu35j5UMtp=LDHJ2RnaQM2qkv6WXqdLzg@mail.gmail.com>
From: Rafael Possamai <rafael@gav.ufsc.br>
Date: Sat, 15 Aug 2015 12:26:15 -0500
To: Glen Kent <glen.kent@gmail.com>
Cc: "nanog@nanog.org" <nanog@nanog.org>
Errors-To: nanog-bounces@nanog.org
Hi Glen,
If you first list the causes of a dropped packet, then you can figure out
how likely they are at different points in time (first\last\peer\etc) by
making some assumptions.
Here's an **example**:
*Cause | Location | Likelihood*
Congestion | Last mile | Low
Congestion | First mile | Low
Congestion | Peering | Medium
Layer 1 | First mile | Low
Layer 1 | Core | Low
Layer 1 | Last mile | High
You can even go as far as drawing a cause and effect diagram for each
location. Then you can collect real world data and fine tune your
assumptions.
Rafael
On Sat, Aug 15, 2015 at 11:47 AM, Glen Kent <glen.kent@gmail.com> wrote:
> Hi,
>
> 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. Sure once it gets off the core, then all
> bets are off on whether it will get dropped or not. However, the key point
> is that the core usually does not drop too many packets - the probability
> of drops are highest in the access side.
>
> Is this correct?
>
> Glen
>
