1. Overlapping eduroam networks operated by different organizations
Jan Furman, CESNET
TNC 2008, Bruges, 21 May 2008

2. Agenda Introduction, potential problems
Problem description (overlapped eduroam networks)
Possible solutions
CISCO unified wireless solution overview
CESNET’s case study
Summary
Q & A

3. Introduction One campus with many different organizations
(e.g. universities)
Ideal situation:
No disturbance between wireless networks in the campus
Optimal usage of radio channels and hardware
Transparent roaming between organizations must be ensured (eduroam)
To maximize signal coverage across whole campus (signal overlapping is unavoidable)

4. Potential problems
Radio management (radio channels assignment, radio interference, transmit power, …)
Very complicated network management in case of huge amount of access points
Problem with overlapping different networks with the same SSID (eduroam) – flapping clients

5. Overlapping problem description

6. Overlapping problem description
This problem is mentioned in the eduroam roaming policy document. *
“Overlapping IP-subnets with same SSID is known to be a problem. If this situation occurs the SSIDs of those institutions involved can be changed to 'eduroam-[inst]' (where [inst] is an easily understandable indication of institutions name). If this solution is applied the SSIDs MUST be broadcasted.”
* … GN2 JRA5 deliverable DJ5.1.3, part 2: Policy document, chapter [Confederation member level technical requirements], paragraph 12.

7. Possible solution - 1 SSID with organization related extension
(e.g. “eduroam_cesnet”); mentioned in the roaming policy
Pros:
Easy to implement
It solves the problem of flapping client
Cons:
The beauty of transparent roaming is lost
Requires some configuration on the client side

8. Possible solution - 2
Single VLAN across whole campus - all eduroams are terminated to this VLAN, centralized IP address assignment, strong cooperation is necessary
Pros: It’s better than nothing
Cons:
Very complex AP management – unclear competence
It don’t solve the problem of client flapping completely
Very complex and problematic troubleshooting
Huge IP address space is necessary

9. Possible solution - 3 Wireless Lan Controller (WLC) Pros:
Fast handover between APs is ensured (in scope of whole mobility group)
Effective management of big amount of APs
Automatic control of radio parameters
Rogue AP detection
It solves the problem of flapping client
Cons:
High cost
Proprietary
Centralized solution is provided by many vendors - in this presentation is mentioned only implementation from CISCO.

10. CISCO unified wireless solution - overview
Lightweight APs (conversion from IOS to lightweight)
LWAPP tunnel between WLC and AP
All “intelligence” is on the WLC – AP is just a “remote radio”
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11. CISCO unified wireless solution - overview
WLC is single point of failure – backup is necessary
Fast Secure Roaming – handover time is 50 to 100 ms
Prerequisites:
Cisco Compatible Extensions (CCX)
CCXv2 … CCKM is supported for LEAP only
CCXv3 … EAP-FAST
CCXv4 … other EAPs (EAP-PEAP, EAP-TLS, …)
Cisco Centralized Key Management (CCKM)
Bug in Windows Vista – CCKM is recognized as WEP protected network
Proprietary – CAPWAP is possible solution for interoperability, still in phase of draft

12. Wireless Lan Controller
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13. Wireless Lan Controller
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14. WLC – mobility group
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15. Wireless controllers
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16. CESNET’s case study

17. CESNET’s case study Each organization (6) has its own controller
One centralized backup controller
Each organization has full control over its radio network
Radio coverage around whole campus is optimal because it is centrally controlled by WLCs
No interferences – radio channels are allocated automatically by WLCs
Very good practical experience with this solution

18. CESNET’s case study

19. Summary
Description of problem with flapping client – overlapped eduroam networks
Possible solutions
CISCO unified wireless solution – Wireless Lan Controllers and their application
CESNET’s case study

20. Q & A