Questions about Internet Packet Losses

Craig Labovitz labovit at
Mon Jan 13 23:28:20 UTC 1997

at Mon, 13 Jan 1997 14:00:33 PST, you wrote:
> You quote:
>    "Although some
>    of the packet loss is inadvertent, a large percentage of the public
>    exchange point connectivity problems reflect intentional engineering
>    decisions by Internet service providers based on commercial settlement
>    issues.
> I think that this is an _extremely_ dangerous assertion on Merit's part.
> As always, ascribing intent rather than raw data requires much more
> justification which I have yet to see.

Unfortunately, a key word here was probably left out. The sentence should have 
read "_may_ reflect"... Tony is right -- we cannot ascribe any 
motives/rational to ISP engineering decisions.

We are walking a bit of a tightrope here. Although I believe the NetNow 
statistics contain some valuable information on network performance, a number 
of large ISPs have expressed significant concerns about the possible 
misinterpretation of the data. Specifically, several ISPs have explained that 
increasing amounts of their customer traffic do not traverse public exchanges. 
These ISPs assert that measuring packet loss/latency between public exchange 
points is not reflective of actual network performance as perceived by their 
customers. These ISPs further explained that their priority is always to 
optimize their customers' network performance. For the large ISPs, this 
increasingly may mean prioritizing connectivity to direct/private exchange 
points before public exchange points.

Of course, I have not seen publicly available statistics on the amount of 
traffic traversing public exchange points versus private exchange points. The 
text Bob quotes essentially reiterates the explanations/descriptions of the 
NetNow data provided by the large ISPs. Lacking any evidence to the contrary, 
we included the text as an attempt to provide a more balanced view of the 

>    Where is the data on packet losses experienced by traffic that does not go
>    through public exchange points?
> I suspect that you'd have to ask the parties involved in the private
> exchange point.  I suspect that there are not such statistics currently
> kept, or if so, they would not be willing to disclose them.  Thus IPPM...

A number of large ISPs have volunteered probe platforms at private exchange 
points. We (Merit/CAIDA/NLANR) are now evaluating the possible deployment of 
additional probe machines for inclusion in these network performance studies.

- Craig

Craig Labovitz				labovit at
Merit Network, Inc.			(313) 764-0252 (office) 
4251 Plymouth  Road, Suite C.		(313) 747-3745 (fax)
Ann Arbor, MI 48105-2785

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