Capwap Mailing List: Re: Issue 156: Need more details on use of DNS for discovery

[Pasi.Eronen (Pasi.Eronen]

Works for me.

Best regards,
Pasi 

> -----Original Message-----
> From: ext Pat Calhoun (pacalhou) [mailto:pcalhoun [at] cisco.com] 
> Sent: 07 August, 2008 20:06
> To: Eronen Pasi (Nokia-NRC/Helsinki); margaret [at] thingmagic.com
> Cc: capwap [at] frascone.com
> Subject: RE: [Capwap] Issue 156: Need more details on use of 
> DNS for discovery
> 
> OK, in which case we need to include text in 3.1 that says 
> that if an AC
> uses the non-default control port, then the data port MUST be 
> control+1.
> Specifically, I would propose keeing your original text, and 
> adding the
> following text to section 3.1:
> 
> <new text>
> 3.1.  UDP Transport
> [...]
>    CAPWAP protocol data packets sent from the WTP to the AC use the
>    CAPWAP data channel, as defined in Section 1.4.  The 
> CAPWAP data port
>    at the AC is the well known UDP port 5247.  If an AC permits the
>    administrator to change the CAPWAP control port, the 
> CAPWAP data port
>    MUST be the next consecutive port number.  The CAPWAP data port at
>    the WTP can be any port selected by the WTP.
> </new text>
> 
> OK?
> 
> PatC 
> 
> -----Original Message-----
> From: Pasi.Eronen [at] nokia.com [mailto:Pasi.Eronen [at] nokia.com] 
> Sent: Thursday, August 07, 2008 9:48 AM
> To: Pat Calhoun (pacalhou); margaret [at] thingmagic.com
> Cc: capwap [at] frascone.com
> Subject: RE: [Capwap] Issue 156: Need more details on use of DNS for
> discovery
> 
> Pat Calhoun wrote:
> > 
> > The IANA service name has already been taken care of, and 
> is already 
> > in the IANA Considerations section in -12 (as requested 
> during WG LC).
> 
> > I do, however, have an issue with the last sentence in 
> Pasi's proposed
> 
> > text, as it states that data channel is control+1. However, in the 
> > previous sentence he clearly states that control MAY NOT be the 
> > default (assigned) port. So I would prefer to change the 
> last sentence
> 
> > to:
> > 
> > "Note that the SRV record MAY specify a non-default port number for 
> > the control channel; the default port number for the data 
> channel is 
> > the next port number (control channel port + 1). However, 
> in the case 
> > where the control channel uses a non-default port number, 
> the WTP MAY 
> > perform a SRV lookup with Service name "capwap-data" and 
> Proto "udp".
> 
> > Thus, the name resolved in DNS would be e.g., 
> > "_capwap-data._udp.example.com"."
> > 
> > Comments?
> 
> How would the WTP know whether the data channel is control+1, or found
> by another SRV lookup?
> 
> Something like "If the control channel port in the SRV record is 5246,
> data port is 5247; otherwise, the WTP MUST perform another SRV lookup"
> would work, but IMHO it sounds like unnecessary complexity -- is there
> any reason why the AC can't just pick two consecutive ports?
> 
> Best regards,
> Pasi
>