When looking at any specialization, the deeper you go, the more you realize
how much you still have to learn. As I dig deeper into the Wireless area of
networking, I have discovered just how much details are involved in being a
Wireless Specialist! Although I work in many different Networking areas,
wireless is one where I spend a considerable amount of time and an area I am
getting deeper into.
First, a wireless specialist has got to have a solid understanding of the physical layer they are working with. That's right, I am talking about RF! All that boring talk in your physics class comes to life in wireless. Things like EIRP, dBm and bandwidth are foundational principles that will promise you failure in the wireless realm if you do not understand them. Understanding the electromagnetic spectrum is a wonderful start. This base RF knowledge is a requirement in performing one of the most important tasks that a Wireless Engineer can have, performing a site survey!
Now performing a site survey in and of itself can be a monumental task and takes a lot of time. There are several things to keep in mind just when preparing to do a survey.
1) Understand what the customer wants. This can be one of the hardest things especially if the customer isn't exactly sure what it is they want other than they want their wireless network to just work.
2) Understand what restrictions the FCC or any other regulatory body may impose on your RF environment.
3) Know the facility you are surveying. There may various procedures, policies and even restrictions that you need to keep in mind. For example, you may need a security clearance to even get inside the building before you can start a survey. There may be OSHA and other fire and safety requirements that must be followed.
4) Plan out what type of survey you are doing. Are you surveying for a Data network, Voice, Location or some combination? Each type will have different RF and AP requirements.
Once you have a plan, start your survey. Typically when I do surveys, I will go over a building map and trace the map with colored pencils what kind of walls, doors or windows there are and then import that map into WCS or some other predictive survey tool. Then, I enter such information to give me a semi accurate predictive survey. It’s a lot of work, but worth it. Next, I take a spectrum analyzer and do a walkthrough of the building just to see what potential interference issues I may come up against. You may be surprised at what you find.
Next, is the Layer 2 survey. Here is where you really look at signal strength, plan out channel placements and survey the overall performance and coverage of the AP you are surveying. I will try to place a few temporary APs in locations that I determined with my predictive survey tool. Then I would take a laptop and perform the Layer 2 survey by slowly walking through the building, gathering Wi-Fi stats from my WNIC. Now there are several ways to approach this. I started out just using the Advanced Stats on my Intel Pro WNIC. It gave be the basic information, but really didn't give things like data rates, transmission errors and those real details that happen in a live wireless network. During some studies, I was introduced to Airmagnet and anyone who is serious about doing a quality survey will want it or a tool like it.
Once your survey is complete, I have already walked the building at least 3 times if not more. First to get the details for my map, second, to perform a Layer 1 survey with a spectrum analyzer and then another with a Layer 2 survey.
Now it’s time to deploy your APs! Where are they being placed, how are they being mounted, how are you powering them up? There are many many considerations when deploying APs. I will typically mount APs in the ceiling when possible and will prefer to use Power over Ethernet to power up the devices and using APs with internal antennas. Now there will be special cases where you will want to use APs with external antennas.
During the survey and installation process a big issue is channel allocation. For the 2.4 GHz band, there are only 3 non over lapping channels. You need to make sure that your APs are using these channels and are all being separated from each other. There is nothing worse than causing your own interference problems by placing 2 APs on the same channel right next to each other! Technologies such as RRM are a big help in this regard.
Whew! That is a lot of work and we are just getting started! Now this is just the survey and installation of a Wireless network. There are many other design aspects, such as what kind of security to use. Ah, security. You can't leave your wireless network without it, unless you want a pounding headache that not even morphine can cure! There are 2 aspects to security in Wireless. The first security aspect is authentication. You want to know who is on your network and permit who is and is not allowed to use it. Authentication is the mechanism to do this. There are various forms of authentication. The most popular are Open, which is basically no authentication, mac address authentication, although it is not scalable and very easy to spoof. Then we have EAP (Extensible Authentication Protocol). With EAP, there are various flavors and the Wireless Specialist will be familiar with those flavors and be ready to implement whatever their customer requires. The most popular EAP methods being:
EAP-TLS - which is certificate based
PEAP - uses user credentials passed through a secure tunnel
EAP-FAST - similar to EAP-TLS but does not use certificates, it uses a Pac file instead.
The second part of security is encryption. Typically in today’s networks, TKIP or AES encryption are used. If no encryption is used, it really isn't too hard to sniff traffic out of the air and see what is going on in the wireless world around you. Because I am paranoid, I will typically use a VPN when connected to a public Wi-Fi hot spot, just to provide encryption.
When choosing a security type, there are many considerations. The main consideration is "do your clients support it"? It won't do you good to choose EAP-FAST if your clients don't support it. PEAP and EAP-TLS, WEP and WPA-PSK are the typical methods that most clients support.
Wireless security doesn't stop there. Remember that the wireless network is an extension of the wired LAN and so you need to not only secure the clients and APs via the air, but you need to take measures to secure your APs on the wired side as well. One of the most deadly threats are rogue APs. You know, the APs that are not a part of your network but are seen by your network, either over the air or on the wire. Things like rogue detection, ACLs, MFP, vlans & firewalls, RADIUS servers, weather its ACS, IAS or some other kind of RADIUS server and the Wireless LAN Controller are all used to help protect your wireless network.
Once the WLAN is installed and secured and users are using it all is well, right? Maybe, hopefully, but there may be times where there are problems and you will need to troubleshoot what is going on.
Now, troubleshooting wireless is a little different than your standard wired network. Why? Unless you’re Superman, you can't see the physical layer. Part of troubleshooting a wired network is checking your physical layer. Well in wireless you need to use tools to help you detect and mitigate interference. One tactic is to use the 5 GHz band. Since most interference sources reside in the 2.4 GHz band, I try to use the 5 GHz band whenever I can. I also suggest to clients to try to get wireless devices that are dual band. There are a surprising amount of devices that claim that they are 802.11n, but only support the 2.4 GHz band. A great troubleshooting tool that helps with interference is Cisco's CleanAir technology that is found in their newer APs. These APs have a spectrum chip in them that help identify the interference sources, such as Bluetooth, analog cameras, microwaves and so on.
Also, look at the load of your APs. Remember, APs are half duplex like hubs and are a shared medium. The more clients on your AP, the slower it will get.
What else does a wireless specialist do? Well what is the point of having a wireless network? Usually it’s for mobility reasons. There is little point in having a wireless network if you don't need to roam around and be somewhat mobile. Things like roaming come into play, weather its setting up mobility groups on a controller or using WDS on an autonomous solution. Being mobile is what makes wireless so cool. A wireless specialist is going to make sure that mobility is one of the basic functions of your WLAN and that it works well.
As we live in the days of Unified networks, it won't be too uncommon where Specialists of various areas will work together to create the network as a whole. A Wireless Specialist may work with a Security specialist regarding wireless security. The Wireless Specialist may work with a Routing & Switching Specialist to tie in the WLAN to the wired back bone. The Wireless specialist may work with a Voice expert when a customer requests Voice over WLAN services.
A wireless specialist will also work with outdoor wireless such as MESH and wireless bridging. Although there seems to be many general areas of a wireless specialist and there are, the wireless specialist works with RF as the physical layer to deliver the same applications that we are used to using on the workstation that is plugged into the wall. As wireless continues to explode, you will continue to see a demand for the wireless specialist out in the field. All of today’s coolest gadgets are all wireless devices and they are not going away any time soon!
Ref:
Wireless Specilaist
First, a wireless specialist has got to have a solid understanding of the physical layer they are working with. That's right, I am talking about RF! All that boring talk in your physics class comes to life in wireless. Things like EIRP, dBm and bandwidth are foundational principles that will promise you failure in the wireless realm if you do not understand them. Understanding the electromagnetic spectrum is a wonderful start. This base RF knowledge is a requirement in performing one of the most important tasks that a Wireless Engineer can have, performing a site survey!
Now performing a site survey in and of itself can be a monumental task and takes a lot of time. There are several things to keep in mind just when preparing to do a survey.
1) Understand what the customer wants. This can be one of the hardest things especially if the customer isn't exactly sure what it is they want other than they want their wireless network to just work.
2) Understand what restrictions the FCC or any other regulatory body may impose on your RF environment.
3) Know the facility you are surveying. There may various procedures, policies and even restrictions that you need to keep in mind. For example, you may need a security clearance to even get inside the building before you can start a survey. There may be OSHA and other fire and safety requirements that must be followed.
4) Plan out what type of survey you are doing. Are you surveying for a Data network, Voice, Location or some combination? Each type will have different RF and AP requirements.
Once you have a plan, start your survey. Typically when I do surveys, I will go over a building map and trace the map with colored pencils what kind of walls, doors or windows there are and then import that map into WCS or some other predictive survey tool. Then, I enter such information to give me a semi accurate predictive survey. It’s a lot of work, but worth it. Next, I take a spectrum analyzer and do a walkthrough of the building just to see what potential interference issues I may come up against. You may be surprised at what you find.
Next, is the Layer 2 survey. Here is where you really look at signal strength, plan out channel placements and survey the overall performance and coverage of the AP you are surveying. I will try to place a few temporary APs in locations that I determined with my predictive survey tool. Then I would take a laptop and perform the Layer 2 survey by slowly walking through the building, gathering Wi-Fi stats from my WNIC. Now there are several ways to approach this. I started out just using the Advanced Stats on my Intel Pro WNIC. It gave be the basic information, but really didn't give things like data rates, transmission errors and those real details that happen in a live wireless network. During some studies, I was introduced to Airmagnet and anyone who is serious about doing a quality survey will want it or a tool like it.
Once your survey is complete, I have already walked the building at least 3 times if not more. First to get the details for my map, second, to perform a Layer 1 survey with a spectrum analyzer and then another with a Layer 2 survey.
Now it’s time to deploy your APs! Where are they being placed, how are they being mounted, how are you powering them up? There are many many considerations when deploying APs. I will typically mount APs in the ceiling when possible and will prefer to use Power over Ethernet to power up the devices and using APs with internal antennas. Now there will be special cases where you will want to use APs with external antennas.
During the survey and installation process a big issue is channel allocation. For the 2.4 GHz band, there are only 3 non over lapping channels. You need to make sure that your APs are using these channels and are all being separated from each other. There is nothing worse than causing your own interference problems by placing 2 APs on the same channel right next to each other! Technologies such as RRM are a big help in this regard.
Whew! That is a lot of work and we are just getting started! Now this is just the survey and installation of a Wireless network. There are many other design aspects, such as what kind of security to use. Ah, security. You can't leave your wireless network without it, unless you want a pounding headache that not even morphine can cure! There are 2 aspects to security in Wireless. The first security aspect is authentication. You want to know who is on your network and permit who is and is not allowed to use it. Authentication is the mechanism to do this. There are various forms of authentication. The most popular are Open, which is basically no authentication, mac address authentication, although it is not scalable and very easy to spoof. Then we have EAP (Extensible Authentication Protocol). With EAP, there are various flavors and the Wireless Specialist will be familiar with those flavors and be ready to implement whatever their customer requires. The most popular EAP methods being:
EAP-TLS - which is certificate based
PEAP - uses user credentials passed through a secure tunnel
EAP-FAST - similar to EAP-TLS but does not use certificates, it uses a Pac file instead.
The second part of security is encryption. Typically in today’s networks, TKIP or AES encryption are used. If no encryption is used, it really isn't too hard to sniff traffic out of the air and see what is going on in the wireless world around you. Because I am paranoid, I will typically use a VPN when connected to a public Wi-Fi hot spot, just to provide encryption.
When choosing a security type, there are many considerations. The main consideration is "do your clients support it"? It won't do you good to choose EAP-FAST if your clients don't support it. PEAP and EAP-TLS, WEP and WPA-PSK are the typical methods that most clients support.
Wireless security doesn't stop there. Remember that the wireless network is an extension of the wired LAN and so you need to not only secure the clients and APs via the air, but you need to take measures to secure your APs on the wired side as well. One of the most deadly threats are rogue APs. You know, the APs that are not a part of your network but are seen by your network, either over the air or on the wire. Things like rogue detection, ACLs, MFP, vlans & firewalls, RADIUS servers, weather its ACS, IAS or some other kind of RADIUS server and the Wireless LAN Controller are all used to help protect your wireless network.
Once the WLAN is installed and secured and users are using it all is well, right? Maybe, hopefully, but there may be times where there are problems and you will need to troubleshoot what is going on.
Now, troubleshooting wireless is a little different than your standard wired network. Why? Unless you’re Superman, you can't see the physical layer. Part of troubleshooting a wired network is checking your physical layer. Well in wireless you need to use tools to help you detect and mitigate interference. One tactic is to use the 5 GHz band. Since most interference sources reside in the 2.4 GHz band, I try to use the 5 GHz band whenever I can. I also suggest to clients to try to get wireless devices that are dual band. There are a surprising amount of devices that claim that they are 802.11n, but only support the 2.4 GHz band. A great troubleshooting tool that helps with interference is Cisco's CleanAir technology that is found in their newer APs. These APs have a spectrum chip in them that help identify the interference sources, such as Bluetooth, analog cameras, microwaves and so on.
Also, look at the load of your APs. Remember, APs are half duplex like hubs and are a shared medium. The more clients on your AP, the slower it will get.
What else does a wireless specialist do? Well what is the point of having a wireless network? Usually it’s for mobility reasons. There is little point in having a wireless network if you don't need to roam around and be somewhat mobile. Things like roaming come into play, weather its setting up mobility groups on a controller or using WDS on an autonomous solution. Being mobile is what makes wireless so cool. A wireless specialist is going to make sure that mobility is one of the basic functions of your WLAN and that it works well.
As we live in the days of Unified networks, it won't be too uncommon where Specialists of various areas will work together to create the network as a whole. A Wireless Specialist may work with a Security specialist regarding wireless security. The Wireless Specialist may work with a Routing & Switching Specialist to tie in the WLAN to the wired back bone. The Wireless specialist may work with a Voice expert when a customer requests Voice over WLAN services.
A wireless specialist will also work with outdoor wireless such as MESH and wireless bridging. Although there seems to be many general areas of a wireless specialist and there are, the wireless specialist works with RF as the physical layer to deliver the same applications that we are used to using on the workstation that is plugged into the wall. As wireless continues to explode, you will continue to see a demand for the wireless specialist out in the field. All of today’s coolest gadgets are all wireless devices and they are not going away any time soon!
Ref:
Wireless Specilaist
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