Subject: [Capwap] The issue of WTP Id

From: Richard <[email-masked]>
Date: Tue, 23 Jun 2009 10:09:43 +0800

Hi, Abhijit:

I also discussed the issue 1 (The issue of WTP Id) raised by you with my
co-editor Yong.
Please check the following opinion:

If we use the Base MAC Address in 4.6.40 WTP Board Data, this 4 - Base MAC
Address is not a MUST HAVE Board Data Sub-Element.
If we use the base Bssid in 6.23. IEEE 802.11 WTP Radio Configuration, the
capwap protocol allow this to be changed by AC. ( 5.8 Configuration Status
Response Message and 5.9. Configuration Update Request Message can have
6.23. IEEE 802.11 WTP Radio Configuration). we think here we should use
something not changeable, right?
Could we use the Vendor Identifier + serial number?

Regards
Richard

2009/6/22 <[email-masked]>

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>   1. Thanks Abhijit's comment, please check my comments inline
>      (Richard)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Mon, 22 Jun 2009 08:56:00 +0800
> From: Richard <[email-masked]>
> Subject: [Capwap] Thanks Abhijit's comment, please check my comments
>        inline
> To: [email-masked]
> Message-ID:
>        <[email-masked]>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Hi,  Abhijit:
>
> Thanks you. I am a editor of MIB draft. Please check my comments inline.
> (identified by [Richard].
>
> 1) Q1
>  Section 5.7.  WTP Profile
>  In a centralized WLAN architecture, a WTP profile is used to make
>  configurations such as static IP address for a WTP before and after
>  it connects to the AC.  It MUST contain the serial number [RFC5415
> <http://tools.ietf.org/html/rfc5415> ]
>  of the WTP because the CAPWAP message received from the WTP contains
>  its serial number and the AC uses this serial number to find the
>  corresponding WTP profile.
>
> [Abhijit] A serial number is not guaranteed to be unique. This needs to
> be based on something that is guaranteed to be unique - like the
> AP MAC address.  Need corresponding changes in the rest of the doc
> where serial number is  is used like CapwapBaseWtpIdTC etc.
>
> [ Richard ] Suggest WG decide to use the AP MAC or serial number.
>  Although editors think that serial number is ok, editors could do changes
>  if most people suggest to use the AP MAC.
>
>  2) Q2
>  Another important function of WTP profile is to trigger the creation
>  of WTP Virtual Radio Interfaces on the AC.  To implement this
>  function, a WTP profile MUST include the WTP's model number
>  [RFC5415 <http://tools.ietf.org/html/rfc5415> ], which reflects the
> number of PHY radios on the WTP.  In
>  this way, the creation of a WTP profile triggers the AC to
>  automatically create the same number of WTP Virtual Radio Interfaces
>  corresponding to the WTP's PHY radios without manual intervention.
>  With the ifIndexes of WTP Virtual Radio Interfaces, the operator
>  could configure and manage the WTP's PHY radios through the wireless
>  binding MIB modules.
>
> [Abhijit] In CAPWAP, WTP informs the number of radio's and creates the
> profile. So, instead of assuming number of radios based on Model number, we
> should use that information.
>  In fact, a model number is not indicative of how many radios are
> active.  For example, a modular AP could initially start with one radio,
> and then have another added later - but would be still using the same model
> number.
>
> [Richard] The model number indicate how many radios a WTP could have and
>  it is  the maximum number of radios.
> When the vendors manufacture the AP equipments, the model number
> already decide how many radios a specific AP could have.
> Although WTP would inform the number of radio in use, the number should be
> less than the maximum number decided by the model number.
> If it is required, the drafts could add some text to handle the case
> when radio in use is less than the maximum radios number told by
> the model number.
>
> 3) Q3
>
>  Section 7.2.  Relationship to IF-MIB Module
>  Also, as an ifIndex [RFC2863 <http://tools.ietf.org/html/rfc2863> ]
>  is used as a common handler for a
>  corresponding interfaces in the CAPWAP-BASE-MIB and specific wireless
>  technologies MIB modules, the AC MUST have a mechanism that
>  preserves the values of the ifIndexes in the ifTable at AC reboot.
>
> [Abhijit] This seems to be a very stringent requirement to impose.
> Why do the ifIndexes need to be persistent across AC reboots ?
>
> [ Richard]  It was ever discussed during last IETF 74 meeting
> and had a conclusion at the time: The WG thinks that the mechanism
> brought forward by the editors is accepable.
> I would like send a the slide for the last meeting to Abhijit,
> and it explains a mechanism about persistence of the ifIndex.
>
> Regards
> Richard
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From: "Abhijit Choudhury (achoudhu)" <[email-masked]>
Date: Wed, 24 Jun 2009 15:49:18 -0700

Hi Richard,

Thanks for your response.

Here're my thoughts on this three topics:

1.  WTP Profile.  While it's possible to use the
(VendorId+SerialNumber), I really suspect that a MAC address is more
appropriate and something most vendors will end up using. To your point
about the Base MAC Address not being a MUST, RFC 5415 seems ambiguous
about it. It says:

            Board Data Type:   The Board Data Type field identifies the
data

              being encoded.  The CAPWAP protocol defines the following

               values, and each of these types identify whether their
presence

              is mandatory or optional:

             0 -   WTP Model Number: The WTP Model Number MUST be
included in

                  the WTP Board Data message element.

            1 -   WTP Serial Number: The WTP Serial Number MUST be
included in

                  the WTP Board Data message element.

            2 -   Board ID: A hardware identifier, which MAY be included
in

                  the WTP Board Data message element.

            3 -   Board Revision: A revision number of the board, which
MAY be

                  included in the WTP Board Data message element.

            4 -   Base MAC Address: The WTP's Base MAC address, which
MAY be

                  assigned to the primary Ethernet interface.

Note that while the RFC specifically sates the other types MUST or MAY
be included, it doesn't say so for Base MAC Address.  It says the Base
Mac Address may be assigned but says nothing about whether it MUST or
MAY be included in the Board Data Type.

Another option is the Base BSSID. Again although the spec only says it's
recommended, I suspect most vendors will have it available.

Could we add text to the effect that one can use either the
(VendorId+SerialNumber) as you suggested or the Base MAC Address or Base
BSSID if it's available ?

2.  WTP Virtual Interfaces:  I still don't see the reason to include the
Model number in the WTP Profile. The number of virtual interfaces
depends on the number of active radios. The WTP specifically includes
this information in the WTP Descriptor:

      0                   1                   2                   3

      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     |   Max Radios  | Radios in use |  Num Encrypt  |Encryp Sub-Elmt|

     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     |     Encryption Sub-Element    |    Descriptor Sub-Element...

     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      So, there is no need for the Model number here.

3.  Relationship to IF-MIB.  I went through the slides you sent. I see
that IF there is a desire to have a common handler, having the ifIndex
persist across reboots may be required. But why would we want to impose
this requirement on everyone by making it a MUST.  It's fine to make it
a MAY.  Not everyone may want to have a common handler.  It's not clear
why this is a hard requirement.

Thanks,

Abhijit

From: Richard [mailto:[email-masked]] 
Sent: 2009-06-22 19:10
To: [email-masked]; Abhijit Choudhury (achoudhu)
Cc: Yong Zhang
Subject: The issue of WTP Id

Hi, Abhijit:

If we use the Base MAC Address in 4.6.40 WTP Board Data, this 4 - Base
MAC Address is not a MUST HAVE Board Data Sub-Element.

If we use the base Bssid in 6.23. IEEE 802.11 WTP Radio Configuration,
the capwap protocol allow this to be changed by AC. ( 5.8 Configuration
Status Response Message and 5.9. Configuration Update Request Message
can have 6.23. IEEE 802.11 WTP Radio Configuration). we think here we
should use something not changeable, right?

Regards

Richard

Today's Topics:

Message: 1

Hi,  Abhijit:

1) Q1
 Section 5.7.  WTP Profile

[ Richard ] Suggest WG decide to use the AP MAC or serial number.
 Although editors think that serial number is ok, editors could do
changes
 if most people suggest to use the AP MAC.

 2) Q2

[Abhijit] In CAPWAP, WTP informs the number of radio's and creates the
profile. So, instead of assuming number of radios based on Model number,
we
should use that information.
 In fact, a model number is not indicative of how many radios are
active.  For example, a modular AP could initially start with one radio,
and then have another added later - but would be still using the same
model
number.

Although WTP would inform the number of radio in use, the number should
be

3) Q3

Regards
Richard
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