Subject: [Pce] PCE port number

From: Vishwas Manral <[email-masked]>
Date: Wed, 9 Sep 2009 11:40:25 -0700

Hi,

I looked at the following in the spec:

“Transport Protocol

  PCEP operates over TCP using a registered TCP port (4189).  This
  allows the requirements of reliable messaging and flow control to be
  met without further protocol work.  All PCEP messages MUST be sent
  using the registered TCP port for the source and destination TCP
  port.”

This has been worrying me a bit. Unlike other protocols like BGP or LDP

In BGP it states clearly:

   A BGP implementation MUST connect to and listen on TCP port 179 for
   incoming connections in addition to trying to connect to peers.

and

   BGP's destination port SHOULD be port 179, as defined by IANA.

Why do we have this restriction on source port? It is becoming a
challenging task
in merchant OS.

Thanks,
Vishwas
Vishwas

---

From: <[email-masked]>
Date: Thu, 10 Sep 2009 10:57:31 +0200

Hi Vishwas.

Interesting comment. We must admit the wording is a bit ambiguous.

RFC 5440 says: "The system listens to the PCEP-registered TCP port" and "Upon receiving a TCP connection on the PCEP-registered TCP port"; I do not see any behavior description for the source TCP port (good thing!).
My guess is that there is no intend to put constraints on the TCP initiator port. I would interpret the sentence you mention as "using the registered TCP port on the PCE side, i.e. for the source TCP port for PCE to PCC messages and for destination TCP port for PCC to PCE messages"... A little cumbersome, I agree.

Authors of RFC 5440, would there be an actual intend to specify otherwise? Implementers, any other interpretation?

Thanks,

Julien

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of Vishwas Manral

Hi,

“Transport Protocol

and

Thanks,
Vishwas
Vishwas
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---

From: Vishwas Manral <[email-masked]>
Date: Thu, 10 Sep 2009 07:50:11 -0700

Hi Julien,

Thanks for your comment. I agree with it. I am actually concerned
about the below statement which in my view means we have to use the
same source and destination port:

"All PCEP messages MUST be sent using the registered TCP port for the
source and destination TCP port.”

I believe the same may not be achieveable in a lot of merchant OS's in
some of the cases. Can the implementors of the same please confirm if
they are using the source and destination port as the PCE port?

Thanks,
Vishwas

---

From: "Adrian Farrel" <[email-masked]>
Date: Fri, 11 Sep 2009 17:33:09 +0100

Hi,

For my part (I only worked as an author quite late in the process, but I was 
helping to get this through the IESG review that raised issued about TCP 
ports) I think Julien has not captured the point.

The RFC is not silent about source ports because it does intend to limit the 
scope.

As Julien says, it does matter which port is listened on, and this is 
deliberately a well-known port number so that it is not necessary to 
configure (or advertise) the port that must be called.

But in Section 4.2.1 you will find...

   Only one PCEP session can exist between a pair of PCEP peers at any
   one time.  Only one TCP connection on the PCEP port can exist between
   a pair of PCEP peers at any one time.

One way to help ensure this is to reduce the number of available ports to 
use as the source port.

Does restricting the source port cause any implementation or deployment 
problems?

Thanks,
Adrian

----- Original Message ----- 
From: <[email-masked]>
To: <[email-masked]>; <[email-masked]>; 
<[email-masked]>
Cc: <[email-masked]>
Sent: Thursday, September 10, 2009 9:57 AM
Subject: Re: [Pce] PCE port number

Hi Vishwas.

RFC 5440 says: "The system listens to the PCEP-registered TCP port" and 
"Upon receiving a TCP connection on the PCEP-registered TCP port"; I do not 
see any behavior description for the source TCP port (good thing!).
My guess is that there is no intend to put constraints on the TCP initiator 
port. I would interpret the sentence you mention as "using the registered 
TCP port on the PCE side, i.e. for the source TCP port for PCE to PCC 
messages and for destination TCP port for PCC to PCE messages"... A little 
cumbersome, I agree.

Authors of RFC 5440, would there be an actual intend to specify otherwise? 
Implementers, any other interpretation?

Thanks,

Julien

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of 
Vishwas Manral

Hi,

“Transport Protocol

and

Thanks,
Vishwas
Vishwas

---

From: Vishwas Manral <[email-masked]>
Date: Fri, 11 Sep 2009 10:01:38 -0700

Hi Adrian,

It would have been ok if it was a connectionless transport like UDP.

However I notice a problem when I want multiple sockets to use the
same port number in particular cases. I figured that I cannot have a
server socket (accepting connections) as well as a client socket
trying to connect having the same port number, though I can allow same
port to be shared across multiple sockets in some cases by using the
socket option SO_REUSEPORT.

Thanks,
Vishwas

On Fri, Sep 11, 2009 at 9:33 AM, Adrian Farrel <[email-masked]> wrote:
> ----- Original Message ----- From: <[email-masked]>

---

From: Vishwas Manral <[email-masked]>
Date: Wed, 16 Sep 2009 11:55:58 -0700

Hi Adrian,

What do you suggest the path forward from here regarding this issue?
Should we just put it in an Errata?

Thanks,
Vishwas