Drops in Core

Mon Aug 17 15:47:28 UTC 2015

Terms get over-used & overloaded in many cases. So it is difficult to tell if this is just a miscommunication, but I think I disagree with this statement.

“Private Peering” in the strictest sense is still peering. You do not have “private peering” with your transit provider, even though the traffic goes over a dedicated link. As such, I do not see how a packet would go over multiple private peering - public or private - links except in a few corner cases such as the ones stated earlier in the thread.

Let’s consider a more general case. Assume a packet traverses several ASes:

      A -- B -- C -- D -- E

There should be no more than one peering relationship in that whole chain, if any. (Zero is a valid number as well.) If, for instance, B peers with C and C peers with D, then who is paying C to do “work”, i.e. to transport packets through fibers & routers inside C's network? It doesn’t even work if B peers with C and D peers with E. Why would C pay D or vice versa when they are not paid on the other side?

The reason peering works is because each peer is paid, either by their own user or a downstream. When traffic goes over a network without being paid at either source or destination, something is wrong. Or worse, when a network pays to send traffic without being paid to receive it, or the reverse, things are very broken.

Even the corner cases still have people paying in some sense. In Bill’s example, networks giving free transit to schools, there is value traded. The ISP providing the service is either expecting more revenue from the school or revenue from others because they transit the school. In the case of a transit provider providing free transit to eyeballs in order to balance ratios, the value is the inbound demand. In Job’s example, you are paying both providers. Even though one has a de-aggregate link, the other is still getting paid. Etc., etc.

If each case, if the expected value does not materialize, the ISP will stop providing the service.

In summary: While there are exceptions to many (all?) rules, we are discussing generalities. And in general, companies who perform work without being paid tend not to last very long.

-- 
TTFN,
patrick

> On Aug 17, 2015, at 10:51 AM, Justin Wilson - MTIN <lists at mtin.net> wrote:
> 
> I could see it going through several private peering, but not through multiple exchanges.  
> 
> 
> Justin Wilson
> j2sw at mtin.net
> 
> ---
> http://www.mtin.net Owner/CEO
> xISP Solutions- Consulting – Data Centers - Bandwidth
> 
> http://www.midwest-ix.com  COO/Chairman
> Internet Exchange - Peering - Distributed Fabric
> 
> 
> 
> 
>> On Aug 16, 2015, at 8:00 AM, Patrick W. Gilmore <patrick at ianai.net> wrote:
>> 
>> On Aug 15, 2015, at 1:41 PM, Job Snijders <job at instituut.net> wrote:
>>> On Sat, Aug 15, 2015 at 11:01:56PM +0530, Glen Kent wrote:
>> 
>>>> 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).
>>> 
>>> It is unlikely packets pass through an IXP more then once.
>> 
>> “Unlikely”? That’s putting it mildly.
>> 
>> Unless someone is selling transit over an IX, I do not see how it can happen. And I would characterize transit over IXes far more pessimistically than “unlikely”.
>> 
>> 
>> [Combining responses]
>> On Aug 15, 2015, at 1:21 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.
>> 
>> I’m a little confused why most packets are “likely to traverse multiple peering points”?
>> 
>> Most packets these days are sourced from one of three companies. (Which Owen should know well. :) At least one of those companies published stats saying the vast majority of packets are “zero or one” AS hop from the destination. I cannot imagine Google or Netflix being 50% behind Akamai on that stat. Which clearly implies most packets traverse “zero or one” AS hop - i.e. one or zero peering points.
>> 
>> Finally, I would love to see data backing up the statement that packets are more likely to drop at one edge (assuming the destination?) than at a peering point.
>> 
>> -- 
>> TTFN,
>> patrick
>> 
> 
> Justin Wilson
> j2sw at mtin.net
> 
> ---
> http://www.mtin.net Owner/CEO
> xISP Solutions- Consulting – Data Centers - Bandwidth
> 
> http://www.midwest-ix.com  COO/Chairman
> Internet Exchange - Peering - Distributed Fabric