We're now going to look at what could go wrong at an internet exchange point and these are generally a list of different ways that exchange point operators harm their exchange point so let's look at the first one and the first thing that can go wrong is the concept some service providers attempt to cash in on the reputation of exchange points the market their for-profit internet transit services as internet exchange part we are exchanging packets with other ISPs so an internet exchange so-called layer 3 exchanges are really internet transit providers and they're using a router rather than an Ethernet switch another thing that can go wrong is financial some exchanges price the i-x out of the means of most providers the whole point of an exchange point is to encourage local peering the acceptable charging model is minimal cost recovery only all members agree on the fees some exchange points charge for port traffic well exchange points are not transit service charging for traffic puts the exchange point in competition with the members transit providers a much more experienced and adapted offering good quality and low cost transit service through it so the exchange point that charges for port traffic will lose of course there's nothing wrong with charging different flat fees for different types of Ethernet ports as they all have different hardware costs on the large chassis switches another thing that can go wrong is competition too many exchange points in one location competing exchanges defeats the whole point of the encouraged local peering exercise because it becomes expensive for ISPs to connect to all of them so they don't or won't and local traffic suffers defeating the viability of the IXPs an exchange point is not a competition and it's not a profit-making business in fact most of the successful exchange points operate purely nonprofit as a cooperative for the members other things that can go wrong include too many rules and restrictions exchange points try to compete with that membership offering service that is peace would offer their customers or provide for their customers in reality exchange points are operated by the members for the members exchange point is run as a closed privileged Club for example very very restrictive membership criteria in reality a participant needs to have an autonomous system number and their own independent address space with that that's all they required to join an internet exchange part sometimes an exchange point is located in a data center with restricted physical or transmission access ixps must be in a neutral location and provide a neutral interconnect with unrestricted physical and transmission access for all members the exchange point charges for traffic well so do transit providers charging for traffic is a sure way of ending the viability of the exchange point I express to end-users rather than just network operators and service providers as already mentioned a participant at an exchange point needs to have their own address space their own and a s number and of course their own transit arrangements exchange points interfere with member business decisions the most common error is enforcing mandatory multilateral peering the exchange point is a layer to infrastructure designed to facilitate local peering the exchange point has no business interfering with how members interconnect the networks over the exchange point fabric there are also many technical design errors interconnected exchange points are often believed to be the solution to a lot of local Internet connectivity issues one exchange point believes it should connect directly to another exchange point in another location it sounds nice in principle but then who pays will interconnect how is traffic metered and this of course is going to compete with the service providers who already provide transit between the two locations who then refused to join the exchange point and probably encourage their customers not to join the exchange point either because they can provide a cheaper service and this harms the viability of the exchange now of course exchange points can have multiple sites within the metro area and this is quite common as exchange points scale and become more and more part of the critical infrastructure in the internet another common error is ISPs bridging the exchange point line back to their offices we are so poor we can't possibly afford a router we'll just connect the exchange point land to our office land well the financial benefits of connecting to an exchange point far outweigh the cost of Hirata in reality it allows the ISP to connect any devices to the exchange point land and this will have disastrous consequences for the security integrity and reliability of the exchange point another thing that can go wrong is routing design errors where a route server is mandated and as we've learned a readily mandatory multilateral peering has no history of success it also means the ISPs have no incentive to learn BGP and therefore no incentive to understand peering relationships peering policies or how interconnects work we become entirely dependent on the operator of the route server for all the troubleshooting all the configuration and the reliability of the interconnect and remember a route server cannot be run by committee and this is what so often ends up happening a route server is designed to assist with scaling peering at exchange parts members of exchange points need to understand peering policies and how the different peering relationships function so summarizing all of what can go wrong an exchange point is not a transit business it is just a layer to switch if charging is going to be implemented fair cost recovery only shared equally amongst all members it's not a competitive service there shouldn't be any oppressive rules or restrictions no mandatory multilateral peering no bureaucratic management no interconnection with other exchange points and no bridging of the exchange point LAN back to members and it's important to use a route server to scale the exchange point.
© Produced by Philip Smith and the Network Startup Resource Center, through the University of Oregon.
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