Internet Exchange Points

The purpose of exchange points is to constitute a regional Internet network segment where ISPs can gather (peer) to exchange local traffic. This measure essentially reduces the number of AS hops that traffic is required to traverse to reach a particular destination prefix. In the old days, this resulted in suboptimal routing to the nearest international network access point (NAP). In the worst case, traffic destined for the same metropolitan network was routed via another continent. Today, with a network of IXs in almost every metropolis of the world, local traffic can be kept local.

The number of AS hops and presence at major exchanges has become a metric often brought up by customers to rate the interconnection quality of carrier services. Modern exchange points provide route servers (and their own AS) to avoid scalability problems with any-to-any peerings. You will read more about this instrument in the section "Route Server and Routing Registries." Therefore, an IX participant only has to set up a peering with the route server.

Historically, exchange points have been known by different names, including the following:

Metropolitan area exchanges (MAEs) (for example, MAE West)
Network access points (NAPs)
Commercial Internet exchanges (CIXs)
Internet exchanges (IXs) (for example, LINX = London Internet Exchange)

In the United States, these exchange points are usually referred to as MAEs/CIXs; in Europe, IX is used more commonly. NAP (network access/attachment point) is a generic term for a location where one can hook up a BGP speaker to other Internet routers. Participants usually acquire dedicated point-to-point circuits to this exchange point (resembling simple network segments; in general, redundant Ethernet switches).

In general, there are two kinds of Internet exchange points: commercial and noncommercial. ISPs can use exchange points to exchange traffic at a national or international level. At the largest exchange points (usually U.S. MAEs), tier 1 and tier 2 carriers gather. These exchange points offer ATM or switched Ethernet ports up to 1 Gbps as an exchange medium.

NOTE

In the beginning, Fiber Distributed Data Interface (FDDI) rings were the exchange medium of choice.

An exchange point (network segment) often constitutes an AS by itself but does not necessarily have to. In 2001, the Euro-IX was founded, an organization that includes almost all IXs in Europe. Internet exchanges usually provide looking glasses and traffic statistics via web interfaces and unprivileged Telnet access to route servers.

Figure 10-2 shows an example of the Vienna Internet Exchange (VIX) web-based looking-glass interface; Figure 10-3 shows the result of this query. The corresponding traffic statistics of this exchange are shown in Figure 10-4. As an alternative, Telnet access to route servers is a convenient way of grasping the way the world sees your prefixes. This is demonstrated in Example 10-2.

Example 10-2. Exodus Route Server Telnet Access


[root@callisto~#] telnet route-server-eu.exodus.net



####################### route-server-eu.cw.net ########################

##################  European Backbone Route Monitor ###################



166.63.210.40    London            166.63.210.41    London



This is the European view of the routes.



For a North American view, telnet to route-server.cw.net

For an Asian view, telnet to route-server-ap.cw.net



This router should be used to see if a route is in CW routing tables.

This router sets local-preference, MED, etc. for all routes equally.

This router should also be used to verify reachability from CW to other

networks.



This router should _not_ be used to verify CW backbone routing policy.

The best path shown is the current best path _from this router_.



For questions about this route server, send email to hno@cw.net



####################### route-server-eu.cw.net #######################



route-server-eu> show ip bgp summary

BGP router identifier 212.62.0.13, local AS number 3561

BGP table version is 54207646, main routing table version 54207646

132963 network entries and 265900 paths using 21937959 bytes of memory

48287 BGP path attribute entries using 2317776 bytes of memory

759 BGP rrinfo entries using 28664 bytes of memory

20064 BGP AS-PATH entries using 488332 bytes of memory

663 BGP community entries using 25760 bytes of memory

Dampening enabled. 0 history paths, 0 dampened paths

BGP activity 987579/854616 prefixes, 3181892/2915992 paths



Neighbor        V    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd

166.63.210.40   4  3561 12854997  121162 54207588    0    0 12w0d      132937

166.63.210.41   4  3561 12851384  121158 54207595    0    0 12w0d      132963



route-server-eu> show ip bgp



BGP table version is 54206927, local router ID is 212.62.0.13

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal

Origin codes: i - IGP, e - EGP, ? - incomplete



   Network          Next Hop            Metric LocPrf Weight Path

*>i3.0.0.0          166.63.210.40                 100      0 7018 80 i

* i                 166.63.210.41                 100      0 7018 80 i

*>i4.0.0.0          166.63.210.40                 100      0 3356 i

* i                 166.63.210.41                 100      0 3356 i

* i6.1.0.0/16       166.63.210.41                 100      0 701 668 7170 1455 i

*>i                 166.63.210.40                 100      0 701 668 7170 1455 i

* i6.2.0.0/22       166.63.210.41                 100      0 701 668 7170 1455 i

*>i                 166.63.210.40                 100      0 701 668 7170 1455 i

* i6.3.0.0/18       166.63.210.41                 100      0 701 668 7170 1455 i

*>i                 166.63.210.40                 100      0 701 668 7170 1455 i

* i6.4.0.0/16       166.63.210.41                 100      0 701 668 7170 1455 i

*>i                 166.63.210.40                 100      0 701 668 7170 1455 i

* i6.5.0.0/19       166.63.210.41                 100      0 701 668 7170 1455 i

*>i                 166.63.210.40                 100      0 701 668 7170 1455 i

* i6.8.0.0/20       166.63.210.41                 100      0 701 668 7170 1455 i

*>i                 166.63.210.40                 100      0 701 668 7170 1455 i

* i6.9.0.0/20       166.63.210.41                 100      0 701 668 7170 1455 i

*>i                 166.63.210.40                 100      0 701 668 7170 1455 i

* i6.10.0.0/15      166.63.210.41                 100      0 701 668 7170 1455 i

*>i                 166.63.210.40                 100      0 701 668 7170 1455 i

* i6.14.0.0/15      166.63.210.41                 100      0 701 668 7170 1455 i

*>i                 166.63.210.40                 100      0 701 668 7170 1455 i

*>i12.0.0.0         166.63.210.40                 100      0 7018 i

* i                 166.63.210.41                 100      0 7018 i

* i12.0.19.0/24     166.63.210.41                 100      0 27487 i

*>i                 166.63.210.40                 100      0 27487 i

*>i12.0.48.0/20     166.63.210.40                 100      0 209 1742 1742 i

* i                 166.63.210.41                 100      0 209 1742 1742 i

...