MREN Architecture and Technology
Overview
The design, development, and implementation of MREN resulted from an extensive analysis of multiple application requirements (especially those of the major inter-organizational scientific research projects) and of currently available and emerging technologies. Regional connectivity provided by MREN is currently based on high-performance Asynchronous Transfer Mode (ATM), which is used to interconnect member sites. However, the MREN community is currently designing a new infrastructure based on infrastructure capable of supporting Gbps, 10 Gbps and multiple 10 Gbps streams. The initial implementation is based on GE switching fabrics at a co-location site at the StarLight facility (www.startap.net/starlight). However, MREN is also prototyping a new type of infrastructure based on Gbps, 10 Gbps and multiple 10 Gbps streams based on lambda switching, supported by advanced optical fabrics – the next geration MREN or the "Optical MREN." With this design, as with the earlier designs, the requirements of advanced high performance applications, especially e-Science and Grid computing are key. Currently, some members of the MREN community are participating in trials based on a leading edge optical networking testbed.
MREN has a fairly flat design, essentially providing L2 transit. MREN engineers manage a mesh of PVCs, the MREN GigaPOP, at the Chicago NAP. MREN was built on a commercial infrastructure -- the Ameritech Public Data Network (APDN). Ameritech has participated as a partner in this effort, in part, because of the unique research and development characteristics of many technology and infrastructure management components of the project. Originally plans called for a metropolitan ring provided by the Ameritech Public Data Network (APDN). This ring, based on Synchronous Optical Network (SONET) technology, would have consisted of an OC-48 fiber infrastructure (2.48 Gbps). Instead, a star topology was selected. At this time, the MREN community is planning for a new type of foundation fabric based on a mesh of lambdas, each supporting at least a single Gbps stream, with 10 Gbps at the core.
Technical Requirements
When MREN was designed, a key, early decision was to create a communication system that would meet a series of challenging goals: the communication systems had to meet short-term needs, be easily scaleable, allow low-cost expansion to meet future needs, especially for future advanced applications, and take advantage of emerging technologies, while remaining compatible with existing communication systems. Also, it had to provide eventually access paths to other regional networks and to national and global networks. The resulting design was consistent with the strategic technical directions of the MREN consortium, and it has provided a useful model for other research and education infrastructures requiring advanced technologies. These basic principals are also being incorporated into current design considerations.
After extensive analysis of current and anticipated broadband applications and after balancing the needs of research applications against implementation economics, and after separating immediate technical requirements from highly desirable features and future requirements, the MREN project specified the following requirements:
b) high reliability,
c) security,
d) modularity,
e) standards-based,
f) scaleability,
g) expandability,
h) manageability at all technical layers, and
i) operational at increasingly higher performance over time.
Results
MREN has a proven track record of high quality with regard to all criteria.
High Performance: The communications foundation of MREN is a high performance regional infrastructure backbone. The star topology has allowed MREN to minimize latency. This topology has provided full cell switching connectivity between the sites without the delay of additional hops through routers. The single delay encountered among the sites is the network switching cluster (Ascend). However, for the future, even high performance is required, eg, Gbps, 10 Gbps and multiple 10 Gbps. Consequently, plans are to transition to an all optical foundation switching fabric- to remove ATM and SONET layers and support high performance streams with DWDM lambdas.
High Reliability: Uptime has been close to 99.99%. Using a variety of specialized techniques, even without a SONET infrastructure, reliability should be four 9s or better.
Security: Exceptional security has been provided - security issues has been dealt with through several cooperative projects.
Expandablity: MREN has provided an easy path for other organizations to immediately acquire economical high-speed access to the site on the network simply by obtaining a connection to the APDN. A major strength of this design has been that additional sites (those of existing and new member organizations) have been easily be linked to MREN simply by connecting a local loop fiber build to the APDN infrastructure, allowing immediate switching capability high-speed connectivity among all connected sites. Another advantage is that a variety of different services are available through the same communication infrastructure; not all participants are required to be at the same level. In the future, connections and services will be added by interconnections through lambdas. This type of infrastructure will allow different types of services to be provided through different lambdas on the same physical fibers.
Scaleability: This characteristic has been repeatedly demonstrated since MREN was first established in 1994. The "Optical MREN" should be even more scalable. With SONET, to upgrade to higher speeds, it is necessary to replace core equipment. With optical networking, scalability is possible by adding lambdas on existing fabrics.
Standards-Based: In the 1990’s ATM cell switching technology become increasingly rich in function and features; positive results were continually reported by project teams working on switches and related equipment. The Optical MREN will also be based on emerging industry standards. The MREN community is closely following the work of the IETF and other standards bodies on these issues.
Manageability at All Technical Layers: General net management, as well as specialized techniques, e.g., flow control, IP routing over ATM, has being provided by member organizations. Individual members manage their L3 infrastructure. MREN engineers manage the L2 transit infrastructure, the PVC mesh at its GigaPOP at the NAP, in coordination with the NAP engineer. Ameritech manages L1 and related equipment. MREN has always had a distributed NOC, and this model will probably be maintained in the new environment.
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