batz wrote:
On Fri, 30 Nov 2001, David R. Dick wrote:
:The problem with this idea is that public exchange points need :to be *avoided* when they get too congested. People may start :out trying to minimize number of hops, but I think they eventually :try to minimize total latency.
Indeed. The notion of "hopcount" is objectively meaningless. You can count hops by physical wires, data segments, network hops, AS's or combinations of each (MPLS, GRE, PPP etc).
He may have been trying to suggest the value of having a low latency path to a tier-1 provider, who may have low latency across their backbone and through their cores.
But this is what you get with any good ISP, so I don't understand what makes IX's more special than being connected to UUNet, Exodus, or any other tier-1. In fact, having a connection to a tier-1, who may be at many IX's, would leave you with the benefits of diverse paths to other networks, without the premium of an IX. Especially considering the tier-1 would be doing traffic shaping to minimize latency across the backbone.
Also, I wonder if you can measure latency reliably over time for more than 3 or 4 'hops' out, and relative to a small number of destinations, before your results cease to be relative to each other? I'm sure there is a principle like this acting upon the Internet somehow.
Without latency measurements for the media you are counting hops in, you might as well count sheep. I think the engineer mentioned at the beginning of this thread was trying to hoodwink and bamboozle you.
Folks, I'm stood to one side up to now, but now this thread is drifting over to personal abuse. I was the engineer in question, and I was most certainly not trying to hoodwink or bamboozle. Neither am I an ignorant sales-droid, as someone else has said. Those of you who know me, as I think that a fair number of people on this list do, will vouch for my honesty, and my pedigree in the industry. I think Alex misunderstood what I was trying to say, and since we were shouting at each other down a very bad phone line with a loudspeaking phone at either end, he's got a certain amount of excuse. Firstly, I've been designing IP networks since the late 80s, and ISPs since the early 90s. I'm not "fresh out of cable school" to quote one correspondant. I've set peering policy for at least 2 large ISPs (BTnet and Level3 (Europe)). Peering is my field of expertise. I'm on the council of the LINX, which is the biggest peering point in Europe. I've also got experience of selling internet services in Europe, and to be frank, the customers over here have different requirements than over in the US. The first thing you get asked is "how good is your peering". They then ask you how much private peering you have, despite the fact that IXPs in Europe tend to be well run and uncongested. What I was offering him was a LAN extension service. One of the things you can use this for is to peer with other customers. It looks like a direct peering (so you keep customers happy) and it gets the bits from A to C without passing through (possibly congested and oversubscribed) B. Its not an oversubscribed service, so you get effectively private line performance. And the costing is distance independent, which makes it more like a peering point, in charging terms. Hope this sets the record straight. Note that I'm posting this from my home email address, and I'm speaking on my own behalf, not that of my company. All the best Nigel