The Open Peering MLPA Registry maintains a MLPA Participants list of all parties which have signed the standard Open Peering Multi-Lateral Peering Agreement (MLPA) . The registry further publishes which of the MLPA Participants have implemented the MLPA using the Open Peering MLPA Routing service in Amsterdam over the AMS-IX, NL-ix or GN-ix Internet Exchanges and what routes they announce.
By signing and registering the MLPA, a network openly makes a policy statement and sustains its commitment to the concept of open peering with anyone. Such open peering policy is defined as the willingness to peer with every other party that abides (signs) the same basic-rules for peering, as laid down in the MLPA.
By implementing the MLPA using the Open Peering MLPA routing service, parties instantly get free of charge routing to all other current and future MLPA Participants that use the same service. This saves a lot of work and maintenance, and helps promote other parties to follow the same open policy.
With one single agreement and one single BGP session a network can arrange instant peering with a large group of peers, instead of negotiating with each of these parties one by one. Further the conditions of the agreement are the same for all peers and require a legal and technical review only once. This saves a lot of time in peering negotiation.
Technically setting up and maintaining one single BGP session which delivers thousands of routes and covers an interesting and relevant percentage of your traffic is much more efficient then using 100 or more separate sessions which deliver only a few routes and generally only a small promillage of your traffic each.
One disadvantage of an MLPA compared to Bilateral Peering is that it is an open-end and all-or-nothing approach. You peer with anyone, as long as they abide the MLPA rules. You cannot exclude a party if you simply do not like them of have a conflict with them for example.
On the other hand, if you do not participate in MLPA Routing, your traffic with such a party would be routed via your Global Transit connection, which is an open-end and all-or-nothing approach as well. In that light MLPA Routing is hardly different then Global Transit, other then that it provides shorter routing paths and is free of charge, where Global Transit is relatively very expensive and has less efficient paths.
A second disadvantage of MLPA Routing compared to Bilateral Peering is that it introduces an extra point of failure in the Open Peering router which provides the service. We therefor advice to set up direct Bilateral Peering sessions to parties you exchange more then 4% of your traffic with, for example the top10 or top25. In any case all routes you receive via the MLPA are always backed up via your Global Transit connection.
How is it different then Bilateral peering
A Bilateral Peering is a peering relation between two parties, one-on-one, which is the most common form of peering. With Multilateral Peering there is a peering relation between a group of networks, documented in a MultiLateral Peering Agreement or MLPA, in which participants agree to peer with all current and future other MLPA participants under the same conditions.
To reach the same coverage in peers, sessions and routes with Bilateral Peering as you have with Multilateral Peering, you would need to connect to multiple Internet Exchanges, negotiate peering with up to a hundred different parties and setup and maintain BGP sessions with all those parties instead of only one. Apart from the initial work maintaining up to a hundred peering relations in all changes in those relations (route changes, parties going away, new parties, takeovers, errors, capacity problems, etc.) brings a continuous workload.
How is it different then NL Routing
A NL Routing product resembles both an MLPA and Global Transit.
You can see NL Routing as a form of an MLPA, but then with a bilateral commercial (paid) relation between you and the carrier, which offers much more routes (about ten times as much), much better local coverage (almost 100% instead of only a few percent) and a commercial service level instead of the best-effort/time-permitting service an MLPA offers.
You can also see NL Routing as a form of Global Transit but then with a local focus and a much lower and flat rate price.
Free, not-for-profit, best-effort, time-permitting
Both the MLPA Registry and MLPA Routing services are free of charge and not for profit services of Open Peering, provided on a time-permitting basis without 24*7 support and theoretically be terminated at any point in time. Of course this is exactly the same service level as is agreed in practically all Bilateral Peering agreements.
Open Peering bears all costs for the router, maintenance of the MLPA Routing BGP sessions, the MLPA Registry and all Internet Exchange port costs for traffic that needs to be transported between MLPA participants with presence on different Internet Exchanges.
Multilateral Peering is always documented in a formal and standard peering agreement: the MLPA. There is generally one party, in this case Open Peering, which functions as co-signer for all MLPA's and keeps a registry of all organizations which have signed the MLPA.
Multilateral Peering can theoretically be technically implemented using a bilateral BGP session between two participants, just as with bilateral peering. In that case the role of the MLPA is limited to the legal agreement.
In most cases however, the technical implementation of an MLPA is done by setting up a BGP session with a an MLPA Routing service, either over an Internet Exchange or over a direct port. In this case Open Peering provides such an MLPA Routing service. Open Peering will redistribute all routes of all participants to all other participants.
Only a single technical configuration action is required to implement peering for all current and future MLPA Participants, and no per individual peer action is needed. This saves a lot of time and work and guarantees the peering is immediately active when a new participant joins the MLPA Routing service.
Payload traffic exchanged directly - Disabled BGP Next-Hop-Self
Where possible only routing information is exchanged via Open Peering and actual payload traffic is exchanged directly between MLPA participants over the Internet Exchange media, without the Open Peering router in between. This is possible as Open Peering re-advertises the routes to all participants with the BGP option Next-Hop-Self disabled. This means on each route the destination IP address of the originator of the route is retained as next-hop, and payload traffic can directly be sent to that party.
Of course this is not possible if participants are present on different Internet Exchanges. Then Open Peering has to carry the traffic between the exchanges from one Participant to the other and is charged by the respective Internet Exchanges for the payload traffic.
On what Internet Exchanges?
Open Peering currently (November 04, 2007) offers an implementation of the MLPA as MLPA Routing Service, on and between the AMS-IX, NL-ix and GN-IX Internet Exchanges. This means that parties which have signed the above MLPA and opted for the MLPA Routing service will get routing to all other signers on any of the above Internet Exchanges.
Internet Routing Registry (RIPE DB/RADB)?
The Open Peering MLPA Routing service does currently not use the routing policy information from the Internet Routing Registry database (maintained regionally by RIPE NCC (RIPE DB), Merit (RADB) and others) for the routing information it supplies to MLPA members or for route filtering purposes.
Instead it just uses/accepts the routing information supplied in real-time by the MLPA participants via BGP4, combined with static AS number and max-prefix filters.
It is however required according to the MLPA that all routes parties announce are registered in the appropriate routing databases.
First MLPA implementation: CIX router
The first MLPA implementation was the Commercial Internet eXchange (CIX) router in 1991, which was decommissioned in 2001. It's role in Internet and peering history is described well in this thesis about the Evolution of Internet Interconnections.
Documentation on Multilateral Peering
There is few good documentation on Multilateral Peering on the Internet. These brief NANOG notes from a BOF meeting in 1997 state advantages and disadvantages of an MLPA.
For participation in and implementation of the MLPA please use the following steps: