Re: Drops in Core

[Sean Donelan <sean () donelan com>]

On Sat, 15 Aug 2015, Glen Kent wrote:
> 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?

1. TCP (and most other IP protocols) depends on, and forces packet 
congestion and drops.  Packet drops alone are not necessarily a 
measure of network quality.  Other than some laboratory conditions,
there must always be some congestion somewhere.

2. Packet queuing and drops are most likely at network transition points. 
Usually speed or latency transition points, but also network 
administration transition points.

3. Packet queuing and drops are less likely between network transition 
points, i.e. across the same network (LAN, WAN, ISP, etc).

That's why some ISPs claim they have 0% packet loss on their network. They 
don't include network transition points in their statistics; but have 
worse end-to-end performance than another network which includes 0.1%
packet drops in their reported statistics.

Generally I don't believe ISPs that claim 100% uptime or 0% packet loss.