| Full title | Information technology. Generic cabling for customer premises. Part 5: Data centres |
| Publisher | ISO and IEC, prepared by ISO/IEC JTC 1/SC 25 |
| Current edition | Edition 1, November 2017, with Corrigendum 1:2018 |
| Status | Published and current |
| Replaces | ISO/IEC 24764:2010 and its Amendment 1:2014 |
| European equivalent | EN 50173-5:2018, published in the UK as BS EN 50173-5:2018 |
What it covers
ISO/IEC 11801-5 specifies generic cabling within and to the computer room spaces of data centre premises. It also applies to computer rooms inside other types of building.
A data centre site often includes offices and plant areas too. Those spaces are covered by other parts of the series:
- office spaces: ISO/IEC 11801-2
- industrial spaces: ISO/IEC 11801-3
- distributed building services in data centre spaces: ISO/IEC 11801-6
It must be read with ISO/IEC 11801-1, which holds the class limits, component categories and test requirements.
Functional elements
The cabling is a hierarchy that runs from the point where external services enter to the outlets at the equipment cabinets.
| Element | Role |
|---|---|
| External network interface (ENI) | Point of connection to external (access provider) networks |
| Main distributor (MD) | Central distributor for the computer room |
| Intermediate distributor (ID) | Distributor between the MD and the zone distributors |
| Zone distributor (ZD) | Distributor that serves a zone of equipment cabinets |
| Local distribution point (LDP) | Optional connection point in the zone distribution cabling, between the ZD and the EO |
| Equipment outlet (EO) | Fixed outlet at or in the equipment cabinet where zone distribution cabling ends |
The cabling subsystems are named after the distributors they connect:
- network access cabling: from an MD, ID or ZD to the ENI
- main distribution cabling: MD to IDs or ZDs
- intermediate distribution cabling: ID to ZDs
- zone distribution cabling: ZD to EO, optionally via an LDP
Classes and media
| Media | Recognised in EN 50173-5:2018 |
|---|---|
| Balanced channel and link classes | EA, F, FA, I and II |
| Balanced cable categories | 5, 6, 6A, 7, 7A, 8.1 and 8.2 |
| Cabled optical fibre categories | OM3, OM4, OM5, OS1a and OS2 |
The ISO text uses the same class range, EA to FA plus I and II. It gives zone distribution length assumptions separately for Classes EA to FA and for Classes I and II, with channel length equations for each. Classes I and II are limited to short channels of up to 30 m with no more than two connections, as set by ISO/IEC 11801-1.
Other tables give length assumptions and equations for cabling between distributors and for network access cabling, and list the connecting hardware to be used at the EO.
Changes from ISO/IEC 24764
- Restructured to hold only requirements specific to data centres, with common requirements moved to ISO/IEC 11801-1
- Balanced cabling channels Class I and Class II added
- Examples of structures added in Annex C
- Examples of networking architectures added in Annex D
How it relates to other standards
- EN 50173-5:2018 is the European equivalent and uses the same structure. It supersedes EN 50173-5:2007 and its amendments. BSI publishes it as BS EN 50173-5:2018, which supersedes BS EN 50173-5:2007+A2:2012.
- ANSI/TIA-942 is the North American data centre standard. It defines its own data centre spaces, while ISO/IEC 11801-5 defines functional elements. TIA-942 also covers site, electrical, mechanical and resilience topics that ISO/IEC 11801-5 does not.
- ISO/IEC 11801-1 sets the performance of each class and category.
- BS EN 50174-1 and -2 cover installation planning and practice, including data centre spaces.
What it means in practice
- Name the distributors on drawings using the standard terms (ENI, MD, ZD, LDP, EO) so designs can be checked against the length tables.
- Use the channel length equations in the standard, not the 90 m / 100 m office rule, when a zone channel includes an LDP or extra connections.
- Confirm the class required at each subsystem. Class I or II is only for short channels, such as within a row.
- Specify cabled fibre by category (for example OM4 or OS2) and state the connector at the EO.
- Check that test reports use ISO class limits where ISO/IEC 11801-5 or EN 50173-5 is the contract standard.
Related reading: OM4 vs OM5 fibre: what’s the difference? · Single-mode vs multimode fibre explained.