First some history.
Until 1994, the MU campus backbone was a 16Mb token ring. Each router had an interface on the ring. These Bay Networks routers were state of the art at the time. They were capable of 10Mb ethernet, 16Mb token ring, and WAN connections such as a T1 or Frame Rely connection. In 1994 networking began to role out ATM (asyncronous transfer mode) technology from IBM. The backbone speed of the ATM was OC-3 running at 155Mbs. To make a long story short, ATM by IBM didn't pan out too well. The project was halted at about 30% conversion. Last year the University signed a contract with Nortel Networks for a completely new data network. The ATM and legacy routed infrastructure would be removed and replaced with an gigabit ethernet backbone, and 10/100 switched ethernet to the desktop.
The hardware.
The heart of the new layer3 gigabit backbone is ran on Nortel Networks Accelar 1200 routing switch. As seen in the picture, this is a highly modular switch. It has a 7gbs backplane, dual redundant power supplies, dual redundant switch fabrics and eight modules. Slots four and five are reserved for the silicon switch fabric. The other slots can be filled with a variety of modules. We are using only 3 different types. Dual LX (single mode fiber) gigabit interfaces. Dual SX (multi mode fiber) gigabit interfaces. And finally a 16 port 10/100 RJ45 card. For more technical information about the Accelar 1200 click HERE
At the edge, we are running a slightly smaller switch. The Accelar 1150 is in the same family as the 1200 and it shares many of the same features. It too has a 7gbs backplance, dual redundant power supplies. It only has one switch fabric, three fixed SX gigabit ports, and two modular slots. The two modules we have been using have been a dual LX gigabit module for the uplink to the core, and a dual SX gigabit module for access ports. For more technical information about the Accelar 1150 click HERE
For enduser access we are employing the Baystack 450-24T and 12T. The 450 is a 12/24 port 10/100/1000 switch. Each access port is 10/100 autosensing switched. Every access port can run either half or full duplex. The 450 alone has a single power supply and switch fabric. It has two type of module interfaces. The first is its MDA or media dependant adaptor interface. For this module we are using a single port SX or LX gigabit module for the uplink. The other slot is used for cascading purposes. The cascade will connect up to 8 switches together. In this cascaded configuration, the switches can share the uplink port and one IP address for management purposes. By cascading the switches another 2.5gbs backplane is brought up in addition to the 2.5gbs backplane that each 450 has. For more technical information about the Baystack 450 click HERE
Several other smaller layer 3 routers have already been deployed on campus, and we will continue to use them. The Nortel Networks BCN router will continue to service our wan connections (T1 and Frame). Two BLN-IIs, which is a smaller version of the BCN, will stay to route the trunked AppleTalk traffic. These routers are not capable of doing layer 3 switching. The reason for keeping them is two fold. First, the Accelar family is unable to route AppleTalk. Second there is not an option of running WAN links yet off the Accelars yet.
The logical and physical design.
The single mode fiber backbone on campus pulls to two major locations, the Telecom node room and the North node room. Each node room has an identical core structure of three core Accelar 1200s, one BLN-II router, and one BCN router. Both node's Accelar core switches have a surrounding aggregate core which is composed of more Accelar 1200s. Currently there are 6 in Telecom and 6 in North. Each campus building plugs into a port on an aggregate core switch. The aggregate core's role is to provide port density for all the buildings and other data network services that the campus uses.
The logical design of network is broken down into VLANs. The core uses its own VLANS, the aggregate core has there own, and each building has its own VLANS. The diagram explains a little more.
Click here for the Visio Diagram