I've read several presentations from cabling manufacturers about the TIA-942 datacenter standard. One aspect seems to be: connect the Main Distribution area to multiple Horizontal Distribution Areas with "core" fiber links; connect from there to each rack with fiber (or copper), optionally cross-connecting in a "Zone Distribution" along the way.
I'm trying to apply this to a co-lo datacenter model, but where do private co-lo customer T1s fit? Telco carrier service (e.g. M13 mux) happens back in the Main Distribution Area, but the only connectivity to the Horizontal Distribution Area is via "core fiber" links?
I'm the co-chair of the TIA TR-42.1.1 working group that developed TIA-942 and the primary contributor to that standard.
You are permitted to install optical fiber, 75 ohm coaxial cable, or twisted pair for both backbone and horizontal cabling. Backbone cabling includes cabling from the entrance room to the Main Distribution Area (MDA) and cabling from the MDA to the Horizontal Distriubtion Area (HDA). Horizontal cabling is the cabling from the HDA to the equipment racks or Equipment Distribution Area (EDA).
If the T1's are terminated in the entrance room, you would use preferably Category 5e or 6 cable from the entrance room to the MDA, from the MDA to the HDA, and from the HDA to the equipment rack where the customer's equipment is located.
You do have to be careful of the distance restrictions. TIA-942 specifies the maximum distances for T1's over 24 AWG Cat 5e/6 assuming that you have no customer-side DSX panel (677 ft) and the amount of distance you need to subtract for every intermediate patch panel or outlet (6.4 ft).
Jonathan Jew
J&M Consultants, Inc www.j-and-m.com
co-chair TIA TR-42.1.1 data center working group
co-chair BICSI data center standard subcommittee
US project lead ISO/IEC data center standard
You do have to be careful of the distance restrictions. TIA-942 specifies the maximum distances for T1's over 24 AWG Cat 5e/6 assuming that you have no customer-side DSX panel (677 ft) and the amount of distance you need to subtract for every intermediate patch panel or outlet (6.4 ft).
Yes, I've been trying to juggle the distance restrictions, with the need to avoid costly long home-runs from EDA to MDA. I'm thinking of installing preterminted 24-pair Cat6 from each cabinet when it is built, to an under-floor or end-row ZDA. The ZDA would be connected back to MDA using plenum 25-pair, terminated on the patch field (maybe MRJ21 cassettes). At the time of customer install, we'd have to open the ZDA to make cross-connects, plus the MDA cross-connects. This all gets very expensive.
The cable vendors are hyping fiber cassettes, but we have had very little interest from customers in fiber NICs. Even for high bandwdith apps (backups, etc.), people ask for gigabit copper hand-offs. I will put some fiber out to the ZDAs, but I doubt it will be used much. But hey, times change.
Another interesting thing with the 942 standard, is that it specifies multimode fiber. So-far, the only requests for fiber I've seen were for customers wanting OC3 WAN connections to routers in their cabinets. Trying to run SONET over multimode fiber requires an expensive and awkward mode-conditioning patch-cord. I'd like to run some singlemode from the MDA to ZDAs, along with the multimode.
TIA-942 cabling, or "Dude, where's my T1"?
