Subject: [core] #7: CoAP ports

From: "core issue tracker" <[email-masked]>
Date: Fri, 11 Jun 2010 11:11:52 -0000

#7: CoAP ports
--------------------------------+-------------------------------------------
 Reporter:  zach@…              |       Owner:  zach@…            
     Type:  defect              |      Status:  new               
 Priority:  minor               |   Milestone:                    
Component:  coap                |     Version:                    
 Severity:  -                   |    Keywords:                    
--------------------------------+-------------------------------------------
 The current coap-00 has text on the CoAP port that needs work:

 "4.2.  Default Port

 CoAP SHOULD use a default port of 61616 which is within the compressed UDP
 port space defined in [RFC4944].  As this port is  in the dynamic port
 space, it however can not be reserved for CoAP use."

 On 2010-6-11, at 13:49, Zach Shelby wrote:
 I was just about to make a ticket on this Lars. What do you suggest we do
 here, I mean we can live with ports outside of 61616-61632. Should we
 define a default CoAP port in the registered range, and then recommend
 (SHOULD/MUST?) that a port in the LoWPAN range is also supported on
 6LoWPAN end-nodes?

 Lars:
 I think you should definitely (also) ask for a port in the registered
 range, for deployments that may need this. Whether you want to recommend
 this port as the default I don't know, because the compression then
 becomes slightly less efficient.

-- 
Ticket URL: <http://trac.tools.ietf.org/wg/core/trac/ticket/7>
core <http://tools.ietf.org/core/>

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From: Carsten Bormann <[email-masked]>
Date: Fri, 11 Jun 2010 13:53:56 +0200

On Jun 11, 2010, at 13:11, core issue tracker wrote:

> default port of 61616

There are two aspects to this.

1) What is the port number implied by

coap://some.host/...
as opposed by
coap://some.host:12345/...

There is nothing that would stop us from saying 61616, but we might as well opt for a reserved port.
We just have to remember 61616 never can be a reserved port.

2) Do we have a reserved (what decades ago was called "well-known") port for CoAP, i.e. a port that would allow somebody who knows a host name but not the port number to infer the latter.  Is that a likely scenario, i.e., do we even need that?  We can always transport the port number in the URI.  (We can amplify that point by not even allowing to elide it from the URI, but that is an orthogonal decision, see #1.)

Gruesse, Carsten

---

From: "core issue tracker" <[email-masked]>
Date: Wed, 30 Jun 2010 08:00:53 -0000

#7: CoAP ports
--------------------------------+-------------------------------------------
 Reporter:  zach@…              |        Owner:  zach@…            
     Type:  defect              |       Status:  closed            
 Priority:  minor               |    Milestone:                    
Component:  coap                |      Version:                    
 Severity:  -                   |   Resolution:  fixed             
 Keywords:                      |  
--------------------------------+-------------------------------------------
Changes (by zach@…):

  * status:  new => closed
  * resolution:  => fixed

Comment:

 Fixed in coap-01 with the following text:

 {{{

 4.2.  Default Port

    The CoAP default port number [TBD1] MUST be supported by a server for
    resource discovery (see Section 6) and SHOULD be supported for
    providing access to other resources.  In addition other end-points
    may be hosted in the dynamic port space.

    When a CoAP server is hosted by a 6LoWPAN node, it SHOULD support a
    port in the 61616-61632 compressed UDP port space defined in
    [RFC4944].

 }}}

-- 
Ticket URL: <http://trac.tools.ietf.org/wg/core/trac/ticket/7#comment:1>
core <http://tools.ietf.org/core/>

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From: Kerry Lynn <[email-masked]>
Date: Wed, 30 Jun 2010 08:04:26 -0400

How is a 6LoWPAN's CoAP dynamic port discovered?  Doesn't
this imply a service discovery (e.g. mDNS) function?

-K-

On Wed, Jun 30, 2010 at 4:00 AM, core issue tracker <[email-masked]> wrote:
> _______________________________________________
> core mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/core
>

---

From: Zach Shelby <[email-masked]>
Date: Wed, 30 Jun 2010 15:23:19 +0300

Hi,

> this imply a service discovery (e.g. mDNS) function?

You can use CoAP resource discovery (Section 6) to find resources on other ports, which is required to be running on the default port, or you can use something like DNS-SD if you have no idea where to start looking by trying to resolve _coap._udp.local for example. 

That reminds me, Section 6 needs to include text on how to include the port in the link-value in case it is not the default port. 

Zach

-- 
Zach Shelby, Chief Nerd, Sensinode Ltd.
http://zachshelby.org  - My blog "On the Internet of Things"
http://6lowpan.net - My book "6LoWPAN: The Wireless Embedded Internet"
Mobile: +358 40 7796297