1. Shi Yang David T. Perkins IETF 70th 3 Dec 2007, Vancouver
CAPWAP Protocol and Dot11 Binding
MIB
Shi Yang
David T. Perkins
IETF 70th 3 Dec 2007, Vancouver

2. } Agenda Problem Domain Design Objectives Basic Idea CAPWAP-MIB
CAPWAP-DOT11-MIB
An Example of MIB Usage
Current MIB Work Status
Next Step
General information
for MIB design

3. Problem Domain
The IEEE standards have well-defined MIB for wireless binding technologies such as ,
Current centralized wireless architectures of most vendors do not reuse IEEE MIB standards, while they define some private MIBs.
It will make interoperability impossible; IEEE and IETF WLAN MIBs will be unable to work well together .
We require a way to avoid reinventing the wheel
for Centralized Wireless Architecture.

4. Design Objectives for MIB
To work well under centralized architectures, and provide a way to centrally manage and control
wireless network by SNMP
To be consistent with CAPWAP protocol
To reuse current MIB standards and future extensions for a wireless binding technology
To enable interoperability between vendors
To meet operator requirements for centralized architectures
Reuse
802.11
802.11a/b/g
802.11e
802.11i
802.11k
IEEE WG MIB standards

5. Basic Idea (1/3)
The SNMP agent run on the AC side, and it MAY not be required on the WTP side
MIB files defined separately
1) CAPWAP protocols (CAPWAP-MIB)
2)Wireless binding (CAPWAP-Dot11 MIB)
The CAPWAP-MIB is independent of any wireless binding technologies
The MIB design follows same idea as CAPWAP: Centralized Control
CAPWAP
WTP
Operator AC
SNMP
SNMP Agent
WTP
WTP

6. Basic Idea (2/3)
To decide on the configured and monitored MIB objects is NOT
very difficult, as CAPWAP protocol already defines them well
To be independent of any wireless binding technologies and
Have ability to reuse MIB standards of other SDOs, is the Main
Challenge for design of the CAPWAP MIB
The ifIndex (RFC1213) will play a role in bridging between
MIB standards defined by different SDOs 6

7. Other Wireless Binding
Basic Idea (3/3)
The operator could manage and control the centralized wireless
architectures using multiple MIB standards defined by
multiple SDOs, while keeping them loosely coupled.
Operator
Agent
SNMP
IETF Organization
IEEE WG
Other Wireless Binding
CAPWAP-DOT11-MIB
IEEE MIB
IEEE
802.16
RFID
CAPWAP-MIB
IF-MIB

8. CAPWAP-MIB MIB function Background Information Basic Idea
WTP Virtual Radio Interface 8

9. Function CAPWAP-MIB function:
- From AC to centrally managed and monitored WTPs
- As a generic mechanism, the MIB module is independent of any
specific wireless binding technologies
- The MIB module supports CAPWAP protocol parameters queries
- The MIB module supports showing the WTPs’ current state
- The MIB module supports indicating the “WTP Virtual Radio Interface” and PHY radio’s mapping relationship
- Counters are provided for WTP, radio's reboot event, hardware
failure etc.
- The MIB module provides the various notification like channel-up, join failure, etc.

10. Background Information (1/2)
As centralized Wireless architecture, the operator has to
prepare configuration at AC side before WTPs connects to AC.
For any wireless binding technology, the configuration
and management of radio is very important.
Under centralized Wireless architecture
WTP Id
Identified by
PHY Radio +
Radio Id

11. Background Information (2/2)
As usual, the standard of a binding technology provides MIB
standard for radio management on its own.
For example, according to IEEE WG MIB standards,
the MIB tables such as Dot11OperationTable are able to
support WTP radio configuration.
These tables use ifIndex as the index, and work well under
standalone Wireless architecture
IEEE WG MIB
Identified by
PHY Radio
ifIndex

12. + Basic Idea To reuse MIB objects (defined by SDOs such as IEEE) for
radio is very import
To reuse IEEE WG and other WG’s MIB standards,
the key point is to reuse the idea of ifIndex
To have a way to maintain the mapping relationship between
“WTP id+ radio id” and “ifIndex”
PHY Radio
CAPWAP
IEEE WG MIB
Identified by
Identified by
WTP Id
ifIndex +
How to map to each other?
Radio Id 12

13. WTP Virtual Radio Interface (1/2)
IfIndex can identify an interface in abstract way, and it does NOT
care for an interface’s PHY location (WTP or AC)
AC can have interfaces of “WTP Virtual Radio Interface” ifType,
it will logically represents PHY radios on the WTPs side
It looks like that PHY radios are located on the AC side
Operator can operate radios by MIB tables (such as IEEE
WG’s) with ifIndex of “WTP Virtual Radio Interface”
as Index AC
WTP
Operator
WTP Virtual Radio Interface 1
PHY Radio 1
SNMP
CAPWAP
WTP Virtual Radio Interface 2
PHY Radio 2
WTP Virtual Radio Interface n
PHY Radio n 13

14. WTP Virtual Radio Interface (2/2)
As an Abstract interface, "WTP Virtual Radio Interface" could be used by any wireless binding technology such as IEEE and
The table of capwapRadioBindTable will indicate the mapping
relationship between “WTP id + Radio id” and IfIndex
PHY Radio
IEEE WG MIB
(or any wireless binding)
CAPWAP
WTP Id
ifIndex
INDEX { capwapWTPId, capwapRadioId } +
Radio Id

15. CAPWAP-DOT11-MIB MIB function Background Information
WTP Virtual Radio Interface
Virtual AP 15

16. Function CAPWAP-DOT11-MIB Function:
The MIB module supports the reuse of current IEEE WG MIB standards and future extensions
The MIB module supports the configuration of the MAC mode and tunnel mode for Wireless service
The MIB module supports virtual AP

17. Background Information (1/2)
As centralized Wireless architecture, the operator has to prepare configurations for each wireless at AC side before WTPs are
able to connect to AC
Under centralized Wireless architectures:
Identified by
Wireless Service
Wireless Id
Operator could configure MAC type or tunnel mode for a Wireless service

18. Background Information (2/2)
IEEE WG MIB does not suggest how to support virtual AP
According to IEEE MIB standards, the MIB tables such as
Dot11AuthenticationAlgorithmsTable are able to support
Wireless configuration (such as authentication algorithm),
and these tables use ifIndex as index
IEEE WG MIB
Identified by
Wireless Service
ifIndex

19. Wireless Service Interface
A Wireless service could be abstracted as an Interface, and
which could be identified by ifIndex.
On the AC side, the MIB table CapwapDot11WirelessConfigTable
will indicate the mapping relation between “A Wireless ID” and
ifIndex of a “Wireless Service Interface”
Wireless ID 2
Wireless ID
Wireless ID 3
Wireless Service Interface
With ifIndex of it to reuse IEEE MIBs 19

20. Wireless BSS Interface
Virtual AP
By the table of capwapDot11WirelessBindTable, the operator are able to bind Wireless service to a specific radio through SNMP
Wireless system will dynamically create the "Wireless BSS Interface“
BSS interface will be used for the data forwarding function
Radio
bind
Wireless ID
Dynamically Create
Wireless BSS Interface
Identified by ifIndex 20

21. Summary
CAPWAP-MIB focus in how to manage and control WTP, and how to support any wireless binding through the mechanism of “WTP Virtual Radio Interface”
CAPWAP-DOT11-MIB focus in how to support configuration of MAC type and tunnel mode for WLAN service, and how to support Virtual AP. With “WLAN Service Interface”, it is able to
Reuse IEEE MIB.
Wireless binding related MIB objects will be defined
by IEEE such kinds SDOs
IF-MIB could be used to model interface (such as WLAN Service interface) 21

22. An example of MIB Usage (1/4)
1) The mapping relationship between “WTP Virtual Radio Interface” and “WTP Id + Radio id” (CAPWAP-MIB)
When configuration for a WTP is prepared before it connects to AC, the following information is available in the CapwapRadioBindTable
Identify a WTP
In CapwapRadioBindTable {
capwapWTPId =
capwapRadioId = 1
capwapWTPVirtualRadioifIndex = 10
capwapWirelessBinding = dot11(2) }
Identify a radio
ifIndex of a “WTP
Virtual Radio Interface”
The type of ”Wireless
Binding”

23. An example of MIB Usage (1/5)
2) Operator configure Wireless radio through IEEE MIB
In Dot11OperationTable (Example) {
ifIndex = 10,
dot11RTSThreshold = 2347,
dot11ShortRetryLimit = 7,
dot11LongRetryLimit = 4,
dot11FragmentationThreshold = 256,
dot11MaxTransmitMSDULifetime = 512
……. }
ifIndex of a “WTP
Virtual Radio Interface”
Wireless Radio
Parameter

24. An example of MIB Usage (2/5)
3) Configure wireless service
A) Create a "Wireless Service Interface" through CAPWAP-DOT11-MIB.
In CapwapDot11WirelessConfigTable {
capwapDot11WirelessId = 1,
capwapDot11WirelessServiceIfIndex = 20,
capwapWTPMACType = splitMAC(2),
capwapWTPTunnelMode = dot3Tunnel,
capwapDot11WirelessConfigRowStatus = create }
Wireless ID
ifIndex of “Wireless
Service Interface”
MAC Type and
Tunnel Mode

25. An example of MIB Usage (3/5)
B) Configure Wireless parameters of "Wireless Service Interface"
through IEEE MIB.
In Dot11AuthenticationAlgorithmsTable (Example) {
ifIndex = 20,
dot11AuthenticationAlgorithmsIndex = 1,
dot11AuthenticationAlgorithm = Shared Key,
dot11AuthenticationAlgorithmsEnable = true }
ifIndex of “Wireless
Service Interface”
Wireless
Authentication Parameter 25

26. An example of MIB Usage (4/5)
4) Bind Wireless service to WTP radio
In CapwapDot11WirelessBindTable {
ifIndex = 10,
capwapDot11WirelessId = 1,
capwapDot11WirelessBSSIfIndex = 30,
capwapDot11WirelessBSSRowStatus = create }
ifIndex of “WTP
Virtual Radio Interface”
Wireless Id
ifIndex of “Wireless
BSS Interface”

27. An example of MIB Usage (5/5)
5) Operator query the statistic data
Operator could query statistic data of WTP, radio, station objects by IF-MIB, IEEE MIB (such as dot11CountersTable), CAPWAP-MIB and CAPWAP-DOT11-MIB (such as capwapWTPRebootStatsTable)
Counters refer to
CAPWAP Protocol

28. Current MIB Work Status
The first version(00) of CAPWAP-MIB and
CAPWAP-DOT11-MIB were published in July 2007.
The latest MIB drafts (version 01) are planed to be published
after IETF-70th Meeting.
The co-editor of drafts are Shi Yang and David T. Perkins
Request More Comments from CAPWAP WG

29. Next Step Request CAPWAP-MIB and CAPWAP-DOT11-MIB
to be CAPWAP WG’s Formal Drafts. 29

30. Questions?
Comments?