Roaming is the basic requirement, but most of the time Wi-Fi network has this issue that user is facing seamless roaming or connectivity during moving from one Access point to other access during Mobility. They got connection-disconnection, low signal strength and many other issues.
What is Wireless Roaming
Wireless Roaming is feature in Wi-Fi technology that allows Mobile users to keep connected with APs and access LAN services over WiFi during roaming between one access to another access points.
What is Seamless Roaming
Seamless Roaming refers that, when a WiFi user roam or moving within multiple access points and if a wifi user will not get disconnected or facing any connectivity issue and continue to use Wifi services without any delay or interruption then it is nothing but Seamless roaming. If wireless Network is not designed properly with considering all aspects, then roaming or mobility will not work and user will not roam seamlessly.
Type of Roaming
There are Three type of Roaming:
- Intra-controller Roaming
- Inter-Controller Layer-2 Roaming
- Inter-Controller Layer-3 Roaming
Intra-controller Roaming
Hope, everybody has experienced that whenever you travelling from one state to another state, you get a message from your mobile Network ISP for Roaming charges or Other Network available during roaming. We can understand this like, if you are travelling within your home City, you will not get any roaming messages or Charges and you always connected your Local Mobile network ISP, because that ISP has their network Tower locally in that City.
User will get same speed, IP address and other services without any disconnection.
Same concept applies on Corporate Wireless Network. If an User roaming between two Access Points with in same WLC ( Wireless LAN Controller) then WLC will not do any major changes in their database, because during roam user will have same IP address VLAN, SSID and there are no disconnection or re-association with AP. WLC will only update the client table like AP name and Security parameters only
In below diagram, user-1 was connected with AP-1 on WLC-1, but when he moved or roam, then user gets connected with AP-2 on same WLC-1. then there are no changes in user IP, VLAN etc.. only WLC update client association information from AP-1 to AP-2. This is called Intra-Controller Roaming.
Inter-Controller Layer-2 Roaming
Now let use the same mobile network ISP example. Now User is roaming between two different Cities but in same State. Then still Roaming charges will be not applicable and use will get seamless connectivity. Might be he will get some slowness or interruption but not disconnection.
Let’s apply the same concept in Corporate Wireless network called Inter-Controller Layer-2 Roaming.
As It is Layer-2, then no IP change applies.
In below diagram, there are Two WLC, but both are in same Mobility Group, and because of both WLC are in same mobility group then all policies, WLAN, VLAN, Subnet and other configured, sync and applied on both WLC. So when user-1 roaming from WLC-1, AP-1 to WLC-2, AP-2, there are no change of VLAN and IP. User will not face any connection issues. There can be sometime some slowness and interruption but user will be connected and services will be not disturbed. WLC-2 will update their client association table. That is called Inter-Controller Layer-2 Roaming.
Inter-Controller Layer-3 Wireless Roaming
Again, we will take same mobile network ISP example. Now User is roaming between two different State. Suppose State-1 to state-2. in State-1 user has good network signal, connectivity because of his home network, but when in enter in State-2 might the user will not get service from his local network ISP or user need to connect with another ISP network or with the same ISP network but State-2 network and then user will disconnect, register with new network. Might be user get disconnection, slowness and other issues.
Same happens with Inter-Controller Layer-3 Roaming, if user roaming from WLC-1 to WLC-2 with different VLAN and Subnet with same SSID then user will disconnect and then connect again with WLC-2 network. That is called Inter-Controller Layer-3 Wireless Roaming.
But As it is causing disconnection and user need to take new IP via DHCP, so there are a technology called Anchor-Foreign Controller will help to assign same IP.
What is AP Grouping (Single SSID Multiple VLAN (Interfaces)
Why AP grouping required
In some huge project where Wireless Implementation are executed at area in KMs, with different department, area and requirement. For example, we need to design a Wi-Fi Network in a amusement part which are spread in KM and have different Plays, Games, Rides, Shopping complex, parking, Movie Halls & Restaurant etc. Then all these department doesn’t have same services and have different Wi-Fi Devices like Handheld devices for Ticking, Parking App, internet Services etc.
So, there are no use to broadcast all SSID to all department, it can be a security breach and increase user connection which are not really required.
To full-fill this requirement, we can create AP group where we can:
- Create SSD with their Interface and Mgmt. VLAN IDs
- Created AP groups and give a group name
- Add SSIDs in AP Groups which needs to be broadcast
- Add APs in respective AP groups
- Add Max 100 AP per Groups.
Now only required SSID will be broadcast on the Access Points which are installed for a particular location or purpose.
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FAQ
Q. What is wireless Roaming?
A. Wireless Roaming is feature in Wi-Fi technology that allows Mobile users to keep connected with APs and access LAN services over WiFi during roaming between one access to another access points.
Q. What is Seamless Wireless Roaming?
A. Seamless Roaming refers that, when a WiFi user roam or moving within multiple access points and if a wifi user will not get disconnected or facing any connectivity issue and continue to use WiFi services without any delay or interruption then it is nothing but Seamless roaming. If wireless Network is not designed properly with considering all aspects, then roaming or mobility will not work and user will not roam seamlessly.
Q. How many Types of wireless Roaming?
A. There are Three type of Roaming:
- Intra-controller Roaming
- Inter-Controller Layer-2 Roaming
- Inter-Controller Layer-3 Roaming
Q: What is Intra-Controller wireless roaming?
A: When a User roam with AP-1 to AP-2 with same WLC in Single Mobility Group.
Q: What is Inter-Controller Layer-2 wireless roaming?
A: When a User roam with AP-1 to AP-2 with two different WLC in Single Mobility Group with same IP and VLAN.
Q: What is Inter-Controller Layer-3 wireless roaming?
A: When a User roam with AP-1 to AP-2 with two different WLC in different Mobility Group with different IP and VLAN
