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Clarifications on ESRO SAP Addressing

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Clarifications on ESRO SAP Addressing

>>>>> On Mon, 18 Aug 1997 08:17:17 -0400 (EDT), Scott Bradner <> said:

  Scott> a comment from one of the IESG members about your draft

  Scott> Scott

Harald's observations are correct.

That part of the spec is not clear.

I will fix this problem in the next rev of the spec. 

My responses to  Harald's email follow:

  >> From Mon Aug 18 08:05:50 1997
  Harald> X-Mailer: exmh version 1.6.9 8/22/96
  Harald> From:
  Harald> To: Scott Bradner <>
  Harald> cc:
  Harald> Subject: Re: draft-rfced-info-banan-esro-00.txt
  Harald> In-reply-to: Your message of "Sun, 17 Aug 1997 20:48:03 EDT." <>
  Harald> Mime-Version: 1.0
  Harald> Content-Type: text/plain; charset=us-ascii
  Harald> Date: Mon, 18 Aug 1997 12:47:04 +0200
  Harald> Sender:

  Harald> The broken part of the protocol is this line:

  Harald> 4.6.3  Use of lower layers
  Harald> ESRO protocol uses UDP port number 259.


Section 4.6.3 needs to be expanded to explain that the ESRO SAP
Selector's range is only 16 (4 bits). That the assignment of a UDP
port is part of the application layer. That port 259 (esro-gen) has
been assigned for general usage of esro.

  Harald> The protocol is an obvious alternate to "heavier" RPC protocols,

Glad you feel that way.

  Harald> but has only 8 bits of SAP to differentiate between different users.

It is not 8 bits for the ESRO SAP Selector.
It is only 4 bits (a total of 16).

The design decision to accept a limited ESRO SAP Selector space for
efficiency and to rely on UDP ports for wider use was deliberate.

  Harald> The "obviously right" thing to my mind is to say that the assignment
  Harald> of an UDP port is part of the application protocol.


  Harald> The document is also self-conflicting; see this paragraph:

The conflict is because section 4.6.3 needs to be expanded.

  Harald> 2.4.2  Performer-address

  Harald> This parameter is the address of the ESROS Performer User which 
  Harald> consists of ESRO Service Access Point (SAP) Selector, Transport 
  Harald> Service Access Point (TSAP) Selector (e.g., port number), and Network 
  Harald> Service Access Point (NSAP) address (e.g., IP address).  This 
  Harald> parameter has to be supplied by the invoker of the service.

  Harald> ESROS Invoker User provides the Performer-address parameter for the 
  Harald> ESROS-INVOKE.request primitive. 

  Harald> which seems to call the port part of the address.

Section 2.4.2 is correct. Section 4.6.3 needs clarification.

  Harald> I have no objection to publication, but if you talk to them again,
  Harald> it might not hurt to clarify this part.

Thanks for your comments.


No Subject, Scott Bradner
No Subject, Scott Bradner
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