On Aug 16, 2015, at 8:15 AM, Job Snijders <job@instituut.net> wrote:
On Sun, Aug 16, 2015 at 08:00:55AM -0400, Patrick W. Gilmore wrote:
On Aug 15, 2015, at 1:41 PM, Job Snijders <job@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”.
There is another scenario (which unfortunatly is not that uncommon) where packets could traverse two IXPs, and no transit is sold over any of those two IXs.
Imagine the following:
Network A purchases transit from network B & network C. Network B & Network C peer with each other via an IXP. Network A announces a /16 to network B but 2 x /17 to network C. Network D peers with B via an IX (and not with C) and receives the /16 from B, but note that internally network B has two more specifics covering the /16 received from C and the /16 itself. Network B will export the /16 (received from customer) but not the /17s (received over peering) to its peers.
Because of longest prefix matching, network B will route the packets received from network D over an IXP, towards network C, again over an IXP.
This phenomenon is described extensively in the following Internet-Draft:
https://tools.ietf.org/html/draft-ietf-grow-filtering-threats-07
Good point. Although I have trouble believing it is very common, in the sense that I do not believe it is a large number of packets or percent of traffic. To be clear, I fully believe people are doing the more specifics to provider B but not C. Sometimes there is even a good reason for it (although probably not usually). However, most of the Internet will send traffic directly to B, or even A - especially since most packets are sourced from CDNs[*]. -- TTFN, patrick [*] I’m counting in-house CDNs like Google, Netflix, and Apple as “CDNs” here. Before anyone bitches, trust me, I am probably more aware of the difference between those and a “real” CDN than nearly anyone else. But those distinctions are orthogonal to the discussion at hand.