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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: More Questions of Exchange Points
Ruomei Gao Email: [email protected] On Sat, 6 Apr 2002 [email protected] wrote: > > > > > 1, Some of the exchange points are layer 2 facilities, then why do they need > > > register IP addresses? Furthermore, those IP addresses do appears in the > > > traceroute traces (from the skitter data of caida). Does this mean that these > > > IP addresses are actually in use? > > > > Nearly all exchange points are layer 2. This means that they consist of a > > layer 2 switch, normally Ethernet, on rare occasions ATM or frame relay, > > or even something more exotic. The participating ISPs bring routers, > > which they all connect to the switch. Each of those routers must have an > > IP address in order to communicate with the others, and the IP addresses > > must all be within the same subnet. That being the case, the correct > > procedure is for a block of addresses to be allocated to the exchange, > > rather than through any one of the ISPs, so that the rest of the > > participants aren't dependent upon any one ISP which might be providing > > the address space. Also, that way no ISP is forced to provide transit for > > the exchange-point addresses, which theoretically don't need it. > > Er, -ALL- exchanges have a layer2 component. Some institute > policy at layer 3. Since, in general, we are talking about > INTERNET exchanges it makes sense that IP comes into play. > If there is a shared medium that is used as a single broadcast > domain, then a common subnet makes life easier for everyone. > It is possible to use divergent networks (see Sleepy Bills (woodcock) > list) on the same shared media. His list argues that these > distinct subnets are unique exchanges. My take is that they > are not but that is a nit argument. There are lots of ways to > slice the exchange point. > > > So yes, those addresses are very much in use, but in somewhat the same way > > that the /30 on a point-to-point link would be. As a means for the two > > adjacent routers to communicate, and pass on traffic which is coming from > > and going to points much more distant. > > What he said. It is the Internet after all. > > > > 2, How do you categorize the exchange points into large/local IXs, > > > transit/peering IXs (besides look into the peering policies)? From the number > > > of participants? Or from who are the participants? > > > > The difference between a local and a regional exchange is typically one of > > size of participants. It isn't a technical difference, so it might be a > > little hard to arrive at complete consensus on, with respect to any > > particular exchanges. It's probably safe to say that in the U.S., PAIX in > > Palo Alto, MAE-East ATM, and Equinix Ashburn are regional exchanges, that > > in Europe the LINX and AMS-IX are regional exchanges, and that in Asia > > JPIX, NXP-ISP2, and HKIX are regional exchanges. They're where large > > regional ISPs would go to peer with ISPs from outside the region. A > > regional exchange would often be thought of as one that an ISP from > > outside the region would go to first. > > only the very brave or very foolish will attempt such > catagorization. Posh Bill (norton) clearly points out that > the value of an exchange, like beauty, lies in the eyes/network > of the beholder. local/regional - peering/transit.... the > key thing is "whats in it for me?" > > > > The difference between a peering exchange and a transit exchange is a much > > more easily technically-defined difference: a peering exchange is one > > across which, by and large, the participants just exchange peering routes. > > A transit exchange is one across which many of the participants are > > exchange full transit. The consequences of this distinction are pretty > > far-reaching, and generally mean that only one large peering exchange can > > exist in a region, and it'll be inexpensive, whereas several smaller, more > > expensive transit exchanges can coexist in the same region. Phil Smith, > > Keith Mitchell, and I will be presenting a paper on the topic at the next > > NANOG in Toronto. > > Humph. Difference w/o (significant) distinction. > If -ANY- isp provides transit off the exchange fabric, > does that make it a transit exchange? If not, why not? > > And what about exchanges that have -NO- routing protocol > at all? (can you say ARP.... sure you can.) Not peering > or transit. Or are they? > > For me, the key point is that an exchange acts as an aggregation > point for the participants. Generating value off aggregation > can take many forms. Peering and Transit are but two vectors > that are effected by aggregation. > > > --grumpy bill (manning) >
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