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Next: Ethernet Equipment Up: Communications and Networks Previous: Communications and Networks

What Structured Cabling and Routing Mean to You

Brian Carpenter CN/CS

Article 3.1 in CNL 220 introduced structured cabling and routing, two big changes to the CERN Ethernets that will affect every user. This article gives important practical information.

Handling connections to the new cabling

In a building with the new cabling, each room has one or more white wall boxes bearing yellow labels. Each box has one or two outlets, facing downwards to protect the contacts and cables. For example, in office 31-3-020 there are two boxes, with yellow labels reading ``0020/01'' and ``0020/02'' on the first box, and ``0020/03'' and ``0020/04'' on the second box. The numbers ``01'' .. ``04'' simply identify the four network outlets in this office.

Each outlet has a private cable back to the nearest ``star point''. This is a room at the centre of a star of cables, containing equipment (bridges and routers) fed by the CERN backbone network. However, unused outlets are not connected to the network until a connection request is received.

In fact, there is a variety of requests that users may need to make:

There are more subtle requests as well, such as modifying the registered information about a device, and modifying the network service required. (The various network services are described below.)

The cleanest way to make any of these requests is with a newly developed WWW interface found via the CN home page or directly via http://wwwcs.cern.ch/register. This interface presents a choice of questionnaires to the user. These are intended to be self-teaching, but since the network is complicated, there are many options to be chosen. Some key points are:

After sending a request with the WWW interface, the user will receive e-mail messages tracking its progress. Of course, if necessary the user will be contacted personally for clarification. In any case the user needs an e-mail address registered in the appropriate database (check this using tools such as xwho, phone or emdir, and in case of problems contact the User Consultancy Office in Building 513).

Handling connections to the old cabling

All of the above also applies to the old (co-axial) Ethernet except that no outlet number is needed, and the user does not have to wait until a cable is connected in the star point room. In particular, IP addresses should be requested using the WWW interface. Of course, the old Ethernets continue to suffer from the problem of interference between all the users sharing the same cable.

Services and Routing

The CERN networks will be logically subdivided using ``routers''. These are boxes that largely prevent today's site-wide interference between different computers. The old CERN IP address prefix 128.141 will be progressively replaced by a new prefix 137.138. New addresses will be allocated geographically, so that all workstations on the same local Ethernet segment will have the same local prefix.

Within a building, there will be one or more local networks. As far as possible these will regroup similar computers or groups of colleagues, and each one will be called a ``service''. The main types of service are:

Users making connection requests, as described above, will have to choose one of these service classes. An incorrect choice or incorrect details will probably mean that things will not work properly.

As routers are introduced, users making connection or move requests will get back by e-mail a new IP address with the 137.138 prefix. When a system moves for the first time from the 128.141 prefix to the 137.138 prefix, several parameters must be changed, not just the IP address, and instructions on how to do this will be supplied on a case-by-case basis.

In the future

Three points are mentioned for the future. Firstly, if user groups request them, a certain number of network outlets will be pre-configured and specially labelled for the connection of portable computers. Secondly, when it becomes practicable, we intend to deploy dynamic configuration servers (DHCP servers). Then, portables will not need manual configuration of their IP addresses.

Thirdly, in cases where more outlets are needed than are actually installed in a given office or lab, a small fanout box can be used to provide extra outlets.



next up previous
Next: Ethernet Equipment Up: Communications and Networks Previous: Communications and Networks



Michel Goossens
CN Division
Tel. 3363
Tue Nov 28 18:14:41 MET 1995