Subject: [Capwap] Comments on Draft 3 -- LWAPP

From: Philip Rakity <[email-masked]>
Date: Mon, 12 Dec 2005 13:35:26 -0800

I am a newbie to the group and this the first time that I have read
the internet draft.  I have a number of comments on the draft that
are below.  Most a minor editorial things but some are areas I do not
understand

a) Use of "integer" is not consistent in the document --- most of the
time it means unsigned, sometimes signed (but marked as signed), but
sometimes the phrase "unsigned integer" is used and this then makes
me wonder if the fields marked integer are signed or not.

b) page 32 --  section 5.1 "Discovery requests MUST be sent by an ...
AND when no echo responses are received and the WTP"    I think it
should say that "Discovery requests MUST be sent by a WTP when the
WTP returns to the idle state.   This can occur for example when no
echo responses are received for NeibhborDeadInteval. "

c) Page 35 -- Radio Type --  no 802.11b (only) -- no 802.11n -- no
superG -- no superA

d) Page 37 -- Section 5.2.4  WTP manager control IPV4 address -- do
not understand the text --  is there only one ip address ?  if so --
then the ip address is used to return the interface of the AC.  If
only one address -- how is load balancing done ?

e) Page 41 -- Section 6.1  Join Request  -- 3rd paragraph -- Why the
1596 MTU limit -- how was this number chosen ? == (RIF routes if
vlan ?)  if I use 802.3 then I have seen h/w do 1522 (4 byte vlan
tag) -- some number a little bigger than 1522 and h/w do 16K bytes --
(intel ixp 4xx series) ---  The 16K number is bigger than the 4k SDU
for wireless medium...  Would it be better to base the discovery on
the MTU of the wireless media and work down ?

f) Page 52 -- Section 6.5 and Section 6.6 -- Change item that says
see Figure 2 -- to read see section 2.2

g) Page 60 -- REboot Statistics == this requires the WTP maintain
state to know if the last Failure Type was LWAPP initiated.   Same
comment for Crash count.  No value defined for state not maintained
by WTP.  Add cross reference to section where AC tells WTP to reboot.

h) Page 65 -- Blacklist Entry's  -- This whole area is not good from
my point of view.  When I configure a firewall I say what is allowed
(explicitly) and forbid everything else -- there is no way I can give
a list of trusted stations and forbid everything else.  This makes
live very difficult.  There is room for a blacklist -- but an allowed
list is also needed.

i) Page 70 -- Image Data -- do not understand how this can work --
only 2 fragments allowed -- no count of what is being sent etc -- no
way to detect packet loss ---  why not use data xfer mechanism of
tftp ?  -- the blocks are numbered == etc BUT define a md5 hash of
the whole image and give its length in the initial request.

j) Page 72 -- Section 8.5.1 Decryption Error Report   == add note
about only useful if split mac.

k) Page 72 -- Section 8.5.2   Duplicate IP address == what is a
host ?  Is this a mobile station ?  What about the case of a mobile
station having the SAME mac address as a already connected mobile
station to the WTP.  == only useful if NOT split mac

l) General comment -- there is no command to synchronize  time (set
the clocks) in the WTP to a common time base

j) General comment -- why not use the text in the 802.11 MIB
definitions and the name of the MIB entry where these are used to
configure the WTP

k) Page 94 -- Section 11.3.1 -- WLAN's field -- just do NOT
understand how setting a bit relates to the WLAN ID's used later in
the document -- can you give an example or two ?  Only 16 WLAN ID's
allowed ??/

l) Page 97 -- WLAN ID -- field is 8 bits -- other places in document
16 bits

m) Page 102 -- IEEE 802.11 stats -- Why not pad out Radio ID with 3
bytes of "reserved field" so all other fields are 32 bit aligned or
move it to the end of definition (after decryption errors).

n) Page 105 -- WLAN ID -- picture is 8 bits -- text is 16 bits

o) Page 109 WLAN Capability -- can you rename this and ALL other
fields to use the same terms as the 802.11 base standard or the MIB
(very confusing) -- or cross reference

p) Page 113 -- Country Code -- reference 802.11d since this is the
definition

q) Page 113 -- Rate Set -- is length wrong ?  should be >= 2
otherwise what is definition for rates NOT used

r) Page 115 -- RTS Threshold etc -- use wording from the MIB
definitions for all of these entries and reference mib object

s) Page 119 -- IEEE Antenna length -- length sound be >= 5

t) Page 120 -- Supported rates -- length >= 2 and <= 9

u) Page 122 - WTP Qos -- length is 2 if untagged or 802.1p  -- if
dscp it is 2 + (10)*dscp entries

v) Security -- any reason ssl could not be used even for level 2
encryption?  since the link is PT to PT -- the ip address/header is
not need -- then almost same code as layer 3 -- and the package is
public domain so easy to hack

regards,

Philip

Philip Rakity
[email-masked]

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---

From: "David T. Perkins" <[email-masked]>
Date: Mon, 12 Dec 2005 14:09:06 -0800 (PST)

HI,

You have a long list of items. I would like to get some
clarification on only a single point. Others may want
to comment on other points

On Mon, 12 Dec 2005, Philip Rakity wrote:
<text cut>
> definitions and the name of the MIB entry where these are used to
<text cut>
> [email-masked]

Would you provide a short example.

Thanks,
/david t. perkins

---

From: Philip Rakity <[email-masked]>
Date: Mon, 12 Dec 2005 14:55:47 -0800

Dave,

When I wrote that note last night, I looked up rts threshold in bob  
o'hara book "802..11 handbook - 2nd edition" page 246 as I did not  
have the MIB by the sofa.   The wording in Bob's book is not the same  
as the MIB.

I think a reference to the mib variable would be useful.

regards,

Philip

Philip Rakity
[email-masked]

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From: sujay <[email-masked]>
Date: Tue, 13 Dec 2005 13:12:46 +0530

A few comments see inline
Suj>

-----Original Message-----
From: Philip Rakity [mailto:[email-masked]] 
Sent: Tuesday, December 13, 2005 3:05 AM
To: [email-masked]
Subject: [Capwap] Comments on Draft 3 -- LWAPP

I am a newbie to the group and this the first time that I have read the
internet draft.  I have a number of comments on the draft that are
below.  Most a minor editorial things but some are areas I do not
understand

a) Use of "integer" is not consistent in the document --- most of the
time it means unsigned, sometimes signed (but marked as signed), but
sometimes the phrase "unsigned integer" is used and this then makes me
wonder if the fields marked integer are signed or not.

Suj> IMHO in the Idle State No Discovery requests are sent, once
entering
the Idle state, the SM moves to Discovery state before sending Disc Req
messages.

The section talks about when as you rightly pointed out no echo
responses are
Received for NeighborDeadInterval.

d) Page 37 -- Section 5.2.4  WTP manager control IPV4 address -- do not
understand the text --  is there only one ip address ?  if so -- then
the ip address is used to return the interface of the AC.  If only one
address -- how is load balancing done ?

Suj> If the AC has more than one Interfaces open for the WTP to join, it
specifies each of these ip address's with 
Individual TLV's, 
- right, for single ip interface load balancing cannot be done ,(given
only one AC) the AC should return its own interface
Ip address.

e) Page 41 -- Section 6.1  Join Request  -- 3rd paragraph -- Why the
1596 MTU limit -- how was this number chosen ? == (RIF routes if vlan ?)
if I use 802.3 then I have seen h/w do 1522 (4 byte vlan
tag) -- some number a little bigger than 1522 and h/w do 16K bytes --
(intel ixp 4xx series) ---  The 16K number is bigger than the 4k SDU for
wireless medium...  Would it be better to base the discovery on the MTU
of the wireless media and work down ?

f) Page 52 -- Section 6.5 and Section 6.6 -- Change item that says see
Figure 2 -- to read see section 2.2

g) Page 60 -- REboot Statistics == this requires the WTP maintain
state to know if the last Failure Type was LWAPP initiated.   Same
comment for Crash count.  No value defined for state not maintained by
WTP.  Add cross reference to section where AC tells WTP to reboot.

h) Page 65 -- Blacklist Entry's  -- This whole area is not good from my
point of view.  When I configure a firewall I say what is allowed
(explicitly) and forbid everything else -- there is no way I can give a
list of trusted stations and forbid everything else.  This makes live
very difficult.  There is room for a blacklist -- but an allowed list is
also needed.

Suj> In my opinion blacklisting is to prevent any .11 mgt frames from
passing upto the AC for the current WTP-AC session.
- to blacklist one MAC address and allow others is more exact and
specific rather than knowing ALL those which are
Allowed, either way the one which is allowed will is kept the Radius,
you could put your 'allowed' list there !

i) Page 70 -- Image Data -- do not understand how this can work -- only
2 fragments allowed -- no count of what is being sent etc -- no way to
detect packet loss ---  why not use data xfer mechanism of tftp ?  --
the blocks are numbered == etc BUT define a md5 hash of the whole image
and give its length in the initial request.

Suj> LWAPP has the in-band Image transfer mechanism, some protocols use
what you have specified.

Suj> For both local and split Encrytpion / Decryption is done at the WTP
, so we need to send Error reports
for both cases.

Suj> host here is the WTP itself, MAC address are unique so there should
not be a case of a  mobile station having 
the same MAC address as another one.

l) General comment -- there is no command to synchronize  time (set the
clocks) in the WTP to a common time base

j) General comment -- why not use the text in the 802.11 MIB definitions
and the name of the MIB entry where these are used to configure the WTP

k) Page 94 -- Section 11.3.1 -- WLAN's field -- just do NOT understand
how setting a bit relates to the WLAN ID's used later in the document --
can you give an example or two ?  Only 16 WLAN ID's allowed ??/

l) Page 97 -- WLAN ID -- field is 8 bits -- other places in document 16
bits

Suj>It is to be used a 8 bit field only , the 16 bit( status/wlan field
in header)is just a place holder
For the 8 bit WLAN ID as well as the 16bit Status combination, subject
to usage.

m) Page 102 -- IEEE 802.11 stats -- Why not pad out Radio ID with 3
bytes of "reserved field" so all other fields are 32 bit aligned or move
it to the end of definition (after decryption errors).

Suj> See above

Hope it helps,

Thanks,
Sujay

o) Page 109 WLAN Capability -- can you rename this and ALL other fields
to use the same terms as the 802.11 base standard or the MIB (very
confusing) -- or cross reference

q) Page 113 -- Rate Set -- is length wrong ?  should be >= 2 otherwise
what is definition for rates NOT used

r) Page 115 -- RTS Threshold etc -- use wording from the MIB definitions
for all of these entries and reference mib object

u) Page 122 - WTP Qos -- length is 2 if untagged or 802.1p  -- if dscp
it is 2 + (10)*dscp entries

v) Security -- any reason ssl could not be used even for level 2
encryption?  since the link is PT to PT -- the ip address/header is not
need -- then almost same code as layer 3 -- and the package is public
domain so easy to hack

regards,

Philip

Philip Rakity
[email-masked]

---

From: Philip Rakity <[email-masked]>
Date: Tue, 13 Dec 2005 16:34:31 -0800

<snip>

> Received for NeighborDeadInterval.
Thanks --  So does idle state wait the random time interval and then  
move to discovery or is done in the discovery phase ?
If the initial delay is done in the idle phase then the requirement  
is after no echo packets -- transition to idle phase.

> not

So the problem is the ip address CAN repeat but this is not reflected  
in the definition of the length?
> you could put your 'allowed' list there !

I think there is a use for BOTH cases.  in a secure environment I do  
not want control frames from rogue AP's.
> only

I do not understand how this can work as defined in the text.  I  
understand I could overlay it but it needs a definition.

> , so we need to send Error reports

agree -- if WTP doing encryption/decryption

> the same MAC address as another one.
Can we change text to say WTP -- thanks
Just like there should not be a duplicate IP address in the network  
there should not be a duplicate MAC address, but MAC addresses are  
also soft
the linux command
ifconfig hwether allows one to change the mac address

> For the 8 bit WLAN ID as well as the 16bit Status combination, subject

thanks --   will wait for new document to comment or if you would  
like to send draft before publication I would be willing to have a read.

regards,

Philip

---

From: sujay <[email-masked]>
Date: Wed, 14 Dec 2005 11:22:20 +0530

Philip,

Guess we could wait for the new draft, and thereon work on this thread.

Regds,
Sujay

-----Original Message-----
From: Philip Rakity [mailto:[email-masked]] 
Sent: Wednesday, December 14, 2005 6:05 AM
To: [email-masked]
Cc: sujay
Subject: Re: [Capwap] Comments on Draft 3 -- LWAPP

<snip>

On Dec 12, 2005, at 11:42 PM, sujay wrote:
> responses are Received for NeighborDeadInterval.
>

> only one AC) the AC should return its own interface Ip address.

regards,

Philip