Friday July 4 2008
Information Technology Central Services at the University of Michigan
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UMnet Backbone Network Distribution Layer Switch

The Distribution Layer Switch (DLS) is a set of backbone switches in each building, or building complex, that extends the backbone to that building or complex. The purpose of the DLS is to provide a point of connection for switches/networks in the building or complex. Each set of DLS has two Gigabit Ethernet connectiones to the backbone core. DLS are maintained and operated by UMnet Administration. The initial DLS were funded by ITCom equity and DLS upgrades were to be funded by the local unit.

Based on the fact that DLS have become integral to the provision of reliable backbone network service, the UM Network Working Group recommended in 2007 that their replacement be done in a planned, systematic manner and that the associated costs be built into the UMnet Backbone access fee. This recommendation was approved. The replacement and associated funding model change will begin in FY09.

In the initial design (2002), two distribution layer switches connected unit networks to the backbone. As of FY09, one DLS/building will be funded via the UMnet Backbone access fee. The second distribution layer switch provides redundancy. Some units will want to fund this additional level of reliability and some will not, therefore the capital purchase of the redundant distribution layer switch will be a local unit decision.

The original DLS have or are reaching "end of life" and need to be replaced. ITCom Project Managers will inform units ahead of time when that decision must be made and help coordinate any bulk purchase discounts.