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MediationSystem

Mediation System

A Mediation System is either a stateful or stateless system designed to assist ISPs and network operators with traffic and bandwidth management. The management system allows operators to set specific mediation policies for their networks that are represented by Terms of Service (ToS) and Acceptable Usage Policies (AUP) to end-users.

Stateless and stateful design principles have a long history. For example, the IETF and Internet community put forward two stateless and stateful standards for QoS: DiffServ, and IntServ, respectively. Informally, stateless systems use probabilistic algorithms while stateful systems use deterministic algorithms. These two approaches represent philosophical differences in the Internet and other computer networking endeavors which have a long history.

Stateless mediation systems do not require central control from a management system that constantly interacts with the system elements. Instead, a policy may be set on the individual elements and coordinated holistically through the network by distributed algorithms that can be proven robust. Through one or more portals responsible for setting global policy within the administrative boundary, the entire system may be consistently and securely managed. A stateless system allows for self-optimization whereby the central system only has to specify an overall optimization policy for the network.

Stateful systems require feedback between the individual elements and the management system on a constant basis and typically use bandwidth reservation approaches. These systems require consistent interaction so that the centralized management system may optimize the entire network based on that feedback. In general, stateful systems presume that underlying distributed algorithms cannot be proven robust enough to offer statistically guaranteed (linearly predictable) service. The long history in the difference of the design philosophies goes back to an early and commercially significant debate between Token Ring and Ethernet. It took both theoretical articulation and practical experience to demonstrate Ethernet's technical and commercial superiority and robustness. InterStream expects the same process will occur with the stateless and stateful mediation market evolution. The open design philosophy of Ethernet ultimately won out over a more closed and proprietary design. The InterStream Association has committed itself to pursue an open approach for both the mediation system as well as the protocol development through use of an open source approach.

ISTP does not require a specific mediation design. In other words, either stateful or stateless mediation systems may be used under the MBA model. However, the previously inherent disadvantages and difficulties of stateless models are overcome by using a single management portal to manage mediation policies on the network. This portal may be a managed services portal such as those offered by network equipment providers, or managed by the InterStream media grid operator themselves. Thus a stateless mediation system based on the InterStream model eliminates the end-to-end peering problem of DiffServ-type implementations and through use of the InterStream-specified TCP, also mitigates the effect from dropped packets (see Disadvantages of DiffServ, wikipedia). Aside from the disadvantages listed previously, InterStream sees the following challenges with DiffServ:

  1. DiffServ does not work across the Administrative Boundary. Packets are frequently re-marked when crossing boundaries, and there is not a uniform standard for allowing some packets to receive QoS between various ISPs.
  2. The DiffServ QoS model does not support a precise mechanism to control long-range dependence. The "fractal" or self-similar nature of Internet traffic is not segmented from the amongst the "best-effort" traffic class. Therefore, it is very difficult, if not impossible, to create an "Erlang" formula for Broadband Internet.
  3. DiffServ does not provide fine grain measurement of QoS parameters. Due to both the long-ranged dependence issues and lack of uniform deployment of AQM systems throughout the network, packet loss and delay high have much wider variations than some applications require.

Gateways to support specific proprietary stateful mediation systems from network equipment may be developed to also support the MBA and ISTP. In effect, ISTP can be easily supported by networks which simply adhere to the MBA terms and deploy industry-standard network equipment on their own schedule, or more complex stateful systems supporting ISTP may also be deployed through use of proprietary gateways.

With only the designated TCP system deployed, InterStream expects to prove that the mediation system will enable a linearly predictable model for video streaming. As secure mediation controllers are deployed, statistically guaranteed service levels for streaming may be created in addition to allowing ISPs to set their own mediation policies for their networks.

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Page last modified on June 25, 2012, at 02:03 PM PST