WIRELESS at CERN
Frequently Asked Questions
Table of contents
General Questions
- What is a wireless LAN?
- Why a wireless LAN?
- Where can I access the wireless network at CERN?
- What do I need in order to begin using wireless?
- Where can I buy wireless network cards at CERN?
- Where can I find configuration files for wireless cards bought at CERN?
- Can anybody connect to the CERN wireless network?
- Why do I have to register hardware addresses of my network equipment?
- How can I register my network equipment?
- What is the standard setup for being connected to the CERN wireless network?
- How do I know if I am connected?
- What is wireless roaming?
- How does wireless roaming work inside the CERN laboratory?
- What do I have to do if I lose my wireless connection?
- What can I do when I am connected to the CERN wireless network?
- What is CERN not going to support about wireless?
- Can I install my own access point in my office?
- Can I ask CERN to install wireless in my office?
- Whath is the procedure to follow for getting a wireless installation in the office?
Technical Questions
- How does wireless networking work?
- What is the performance of a (802.11) wireless LAN?
- What is ESSID?
- Which channels are available?
Answers
General Questions
What is a wireless LAN?
A wireless LAN (WLAN) is a network that allows access to the CERN intranet and the Internet without the need for any wires to the users machines.Why a wireless LAN?
The greatest advantage of wireless networking is mobility: people move, networks do not.
Wireless users can connect to existing networks and access data (usually stored centrally) while they are in motion.
From this point of view, a wireless network can be very useful, especially for people coming to CERN on a temporary basis, like a conference, or people wandering around the laboratory for work reasons: they can access the network and work on line all the time just by bringing their own laptop with a wireless card in it.Where can I access the wireless network at CERN?
Public wireless access points at CERN are going to be installed in the official conference rooms (i.e. conference rooms which can be reserved via the booking system on the CERN web site), if the administrators of those rooms apply for a wireless installation. This service is provided in order to facilitate network connections for people holding and/or attending conferences, workshops and meetings.
It should be noted that wireless technology is based on radio waves propagation and, as matter of fact, often large part of wireless access points neighbourhoods are covered by the service. This means that offices and places close to conference rooms can receive, by coincidence, wireless signals.
Moreover, wireless access points can be found in some users offices, in the case that they do not interfere with the official ones in conference rooms. Users can ask CERN for wireless installations in their offices but they are required to pay for the service deployment and maintenance.What do I need in order to begin using wireless?
In order to connect to the wireless Network, you will need the following:- Laptop computer equipped with an external Type II or Type III PC card slot.
- A wireless PC Card
Where can I buy wireless network cards at CERN?
Wireless PC cards (and wireless network equipment in general) can be bought at the PC SHOP of CERN.Where can I find configuration files for wireless cards bought at CERN?
Windows configuration files and related documentation for wireless cards bought at CERN are available on the following location: \\cern.ch\dfs\Applications\BreezeNET.Can anybody connect to the CERN wireless network?
No, not everyone is free to connect to CERN wireless network.
In order to be recognized as a user allowed to wireless connections, you need to officially register your portable PC and the hardware address of your wireless PC card(s) and you need then to configure them with the proper CERN wireless setup.Why do I have to register hardware addresses of my network equipment?
You need to register your laptop and the hardware address of your wireless card(s) in order to be recognized as an authorized user and to automatically configure your PC with the necessary IP information you need, each time you connect to the network.How can I register my network equipment?
In order to register your portable PC and your wireless card(s) you have to go to the following URL http://network.cern.ch/register, and fill in the form that is displayed by clicking the Register Portable menu on the top bar.
If you have already registered your portable PC and you just need to register your new wireless card(s), you can choose the Update Information menu on the same URL and simply update the information related to your laptop.
For the moment this registering procedure is applicable only for people owning a NICE CERN account.
An automatic registration form by the CERN web site is under development for people who need to come to CERN for a few days and use its facilities/services but do not have or need any CERN account.Which is the standard setup for being connected to the CERN wireless network?
In order to be connected to the CERN wireless network you need to configure your wireless PC card with the correct network name (ESSID) which is 'CERN'.How do I know if I am connected?
You can check your network connectivity status by looking at the Status and Activity LEDs on your Wireless PC Card Antenna.
If the Status light is blinking or is on, it means that a connection is being or has been made.
If the Activity light blinks, it means that data is being transmitted.What is wireless roaming?
Wireless networks are radio-based systems that broadcast in a certain frequency band of the radio spectrum. A standard wireless network infrastructure is like the one depicted in the following picture:
It consists of one or more access point(s) -wireless base station(s)- connected to a wired network infrastructure and communicating with one or more wireless end station(s) -wireless client(s)- by using high-frequency radio waves.
Wireless network users can connect to existing networks and are then allowed to roam freely. In wireless networking, roaming refers to the ability for clients to move from one access point coverage area to another without interruption in service or loss in connectivity.
From this point of view, wireless networks can be thought of as working in the same way as mobile telephone networks, where users can wander around in the course of a single conversation because the phone connects them through cell towers.How does wireless roaming work inside the CERN laboratory?
The wireless network at CERN has been planned and deployed in order to give the smallest amount of roaming problems to the users.
Unfortunately, it is not possible to provide CERN wireless clients with the ability of going around the laboratory without interruptions in service or loss of connection. This is due to the large size of the CERN site and to the structure of the wired network (and subnetworks) which wireless access points connect to.
As far as possible, inside one building, wireless users can roam freely without any loss of connection.
Therefore for all access points located in the same building, wireless clients can move from one coverage area to another without experiencing any roaming problem.
The service cannot be guaranteed for wireless roaming amongst buildings and, sometimes, it cannot be guaranteed neither inside the same building (especially in case of big buildings, served by multiple wired subnets).What do I have to do if I lose my wireless connection?
A connection loss can be due to two different reasons: either you moved too far away from a coverage area or you started roaming from a different access point which is not not in the same coverage area of the previous one.
In the first case you should go back to a place close enough to an access point, in order to get back the wireless signal you lost.
In the second case you should disable your PC wireless card and then enable it again. In this way, by connecting again to the wireless network, your PC should automatically configure itself with the new IP information it needs to be able to join the new wireless coverage area.What can I do when I am connected to the CERN wireless network?
Once connected to the wireless network, you can use it as you use the standard wired network: e-mail writing, web browsing, home directory accessing, printing to local network printers, etc.
However, it should be noted that even though wireless networks look attractive for use everywhere, wired networks still give the best performance and speed. In general, a wireless connection works just like a wired Ethernet connection, but wireless bandwidth is shared amongst all users connected via wireless in a given area. This means that network speeds may be much slower when many people are using wireless, and will not be as fast as wired Ethernet.
For permanent network connections, a wired network is definitely the preferable solution.What is CERN not going to support about wireless?
The wireless network at CERN does not replace the fixed network. It is a service offered in order to facilitate access to the network in case of meetings, conferences, workshops. For this reason and because of the inherent limits of the technology, wireless networking is not going to be installed and supported in users' offices.
In few cases, especially when offices are close to conference rooms, some users can have the possibility to access the wireless network from their work place, but this is simply a question of luck and not an officially supported service.Can I install my own access point in my office?
Yes, private access points are tolerated in CERN offices but they are not supported.
In such cases of private installations, the following technology considerations must be taken into account and the associated rules must be respected/applied:
- WLAN channels run from 1 to 13 and dictate which part of the 2.4 GHz spectrum is being used for transmission. Cards can only listen to one channel at a time, and all clients on a WLAN must have the same channel set.
- In order to guarantee optimal operations, the minimum channel separation should be 25 MHz for neighboring base stations sharing the same WLAN.
- According to this and the European spectrum allocation, only three channels can be locally used: channel 1, channel 6 and channel 11.
- CERN policy states that channel 11 is reserved for private base stations owned by users. This means that users are allowed to use their own wireless access-points but they are obliged to utilize only CHANNEL 11 for transmission and to use a private ESSID (different from that of the official wireless network, which is 'CERN').
Can I ask CERN to install wireless in my office?
Yes, you can ask CERN to install a wireless access point in your office.
This is a private service whose deployment and maintenance has to be paid by the requesting person or group and can be supplied only in case the requested installation does not interfere with CERN official base stations.What is the procedure to follow for getting a wireless installation in an office?
In order to apply for a CERN wireless installation in your office, you have to contact NETOPS (E-mail: netops@cern.ch, phone: +41 (0)22 767 49 27) and specify all your needs and the necessary technical information (why you need a wireless access point, where your office is located, ...). NETOPS will then take care of your claim and will start the installation procedure.
Technical Questions
How does wireless networking work?
The 802.11 standard basically defines two modes of working: infrastructure mode and ad hoc mode.In the infrastructure mode, the wireless network consists of at least one access point connected to the wired network infrastructure and a set of wireless end stations. This configuration is called a Basic Service Set (BSS) and it uses access points for all communications, including communications between mobile nodes in the same service area.
BSSs can create coverage in small offices and homes, but they cannot provide network coverage to larger areas. 802.11 allows wireless networks of arbitrarily large size to be created by linking BSSs into an Extended Service Set (ESS). An ESS is a set of two or more BSSs forming a single subnetwork.
Since most WLANs require access to the wired LAN for services (home directories, printers, etc.) they will operate in infrastructure mode.
Ad hoc mode (also called peer-to-peer mode or an Independent Basic Set, or IBSS) is simply a set of 802.11 wireless stations that communicate directly with each other without using an access point or any wired network connection (thus all the stations of a IBSS must be within direct communication range). The smallest possible 802.11 network is an IBSS with two stations. This mode is useful for setting up a wireless network quickly and easily anywhere a wireless infrastructure does not exist or is not required for services, such as a convention center or an airport.
802.11 standards so far:
IEEE standard Speed Frequency band Notes 802.11 1/2 Mbps 2.4 GHz First standard(1997). Featured both frequency-hopping and direct-sequence modulations techniques. 802.11a up to 54 Mbps 5 GHz Second standard(1999), but products not realised until late 2000. 802.11b 5.5/11 Mbps 2.4 GHz Third standard, but second wave of products. The most common 802.11 equipment at the moment. 802.11g up to 54 Mbps 2.4 GHz Not yet standardized. CERN wireless network is built on 802.11b technology. This is a radio-based system that broadcasts in the 2.4 GHz spectrum. It uses direct sequence spread spectrum (DSS) encoding to give a theoretical maximum throughput of 11Mbps.
What is the performance of a (802.11b) wireless LAN?
The nominal bandwidth for the 802.11b is 11 Mbps. In reality, wireless protocol (half duplex communication based on CSMA/CA) requires a lot of data exchange between the users and the base stations in order to establish if the channel is idle and transmission is possible. This fact reduces real network throughput, that cannot exceed of ~5 Mbps.Some tests have been done with Alvarion wireless equipment (i.e. base stations and PCMCAs) in order to prove the real bandwidth capacity of wireless.
It has been found that in a situation of optimal conditions (only one base station without any external interference), the maximum throughput which can be reached is ~4 Mbps. Similar results have been presented in an article by Paul-Andre Rumley and Robert Ritter from EPFL after their study about wireless features and limits.What is ESSID?
The Extended Service Set ID (ESSID) can be thought of as the "name" of the network.
All wireless clients and access points on the same network need to have the same ESSID. Without this machines cannot talk each other.Which channels are available?
WLAN channels run from 1 to 13 and dictate which part of the 2.4 GHz spectrum is being used for transmission. Cards can only listen to one channel at a time, and all clients on a WLAN must have the same channel set.
In order to guarantee optimal operations, the minimum channel separation should be 25 MHz for neighboring base stations sharing the same WLAN. According to this and the European spectrum allocation, only three channels can be locally used: channel 1, channel 6 and channel 11.CERN policy states that channel 11 is reserved for private base stations owned by users. This means that users are allowed to use their own wireless access-points but they are obliged to utilize only CHANNEL 11 for transmission and to use a private ESSID (different from that of the official wireless network, which is 'CERN').
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