Subject: Please comment on my draft: DHCP Option for Call Control Servers

From: Henry Houh <[email-masked]>
Date: Tue, 26 Jan 1999 17:37:02 -0500 (EST)

Hi,

I'm new to this process so I don't know the procedure, though I have
read the info for new IETF folks and other info that I have been able
to find.  If I have submitted this in an improper fashion or not named
it correctly, please let me know the correct way to get this in front
of the working group.

I would like to introduce a draft for a new DHCP option to support
location of call control servers (like an H.323 gatekeeper).  There
are many new products available that have stand-alone IP-telephone
endpoints.  This option would facilitate the setup of these endpoints
so as to eliminate any configuration necessary for these IP telephones
to locate their call control servers.

I have tried to do this in a way that allows other vendors with
products to add to this option, but I would like comments on whether
the method to add a new sub-option is acceptable - I have tried to
mirror the method new options are added, and this may be too
heavyweight a method.  Also, I have not made any assumptions on who
else would like to use this option.

Comments on the draft are appreciated,

Thanks,

Henry Houh
NBX Corporation

Internet Engineering Task Force                               Henry Houh
INTERNET DRAFT                                           NBX Corporation
                                                           November 1998
                                                        Expires May 1999

               DHCP Options for Call Control Servers
              <draft-ietf-dhc-callcontrolserv-00.txt>

Status of This Memo

   This document is a submission to the Dynamic Host Configuration
   Working Group of the Internet Engineering Task Force (IETF). Comments
   should be submitted to the [email-masked] mailing list.

   Distribution of this memo is unlimited.

   This document is an Internet-Draft.  Internet-Drafts are working
   documents of the Internet Engineering Task Force (IETF), its areas,
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Abstract

   This document defines a new DHCP option for delivering configuration
   information to telephony enabled hosts in order to locate a call
   control/signalling server.  The option carries several operational
   parameters that allow multiple call control vendors to utilize this
   field.

1. Introduction

   Telephony is emerging as a network-based application.  The Call
   Control Server option allows telephony or gateway devices which
   cannot independently setup up and signal calls to automatically
   discover an address of a call control server.

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Internet Draft   DHCP Option for Call Control Servers      November 1998

   This specification describes a DHCP option [1] that can carry one or
   several Call Control Server sub-options.  Each sub-option is
   treated as a separate potential call control server by the hosts.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED",  "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119. [2]

2. Call Control Server Option

   This option specifies one or more fields carrying Call Control
   Server information.  The fields that can be carried by this option
   are described in the sections that follow.

   The code for this option is TBD, and its maximum length is 255 octets.

      Code   Len        Sub-Option 1               Sub-Option 2
     +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+--
     | TBD |  n  |  a1 |  a2 |  a3 |  a4 |  a1 |  a2 |  a3 |  a4 |  ...
     +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+--

   The 'Len' field specifies the number of octets containing sub-option
   information within the DHCP option.

   Each sub-option will contain a code followed by a length that
   specifies the number of octets containing configuration parameter
   information within the sub-option.

      Sub    Sub 
      Code   Len        Configuration Parameter(s)
     +-----+-----+-----+-----+-----+-----+-----+-----+--
     |  x  |  n  |  a1 |  a2 |  a3 |  a4 |  a6 |  a7 |  ...
     +-----+-----+-----+-----+-----+-----+-----+-----+--

2.1. Call Control Servers

   This section describes the vendor-specific sub-options.

   Other types/vendors of call control servers can be added by using 
   new sub-option fields.  See section 2.2 for the procedure for
   adding sub-option fields.

2.1.1 NBX Call Control Server Sub-option

   This sub-option specifies the network address of an NBX Call
   Control Server.

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   The code for this sub-option is 1. The length specified in the 'Len'  
   field of this sub-option MUST always be 4 octets.

      Code   Len    NBX Server Address
     +-----+-----+-----+-----+-----+-----+
     |  1  |  4  |  a1 |  a2 |  a3 |  a4 |
     +-----+-----+-----+-----+-----+-----+

2.2 Procedure for adding call control server types

   A vendor may add a new sub-option field by issuing an internet
   draft that contains the new sub-option.  The new sub-option field
   code MUST be labeled "TBD."  This draft will then be submitted to
   the DHC working group, and, if accepted for inclusion in the DHCP
   specification, a sub-option field code is assigned and the
   sub-option specification is published as an RFC which updates this
   RFC.

3. Using Multiple Sub-options

   More than one sub-option field MAY be returned to the host.
   In addition, more than one of any sub-option type MAY be present.
   This allows the host to select the call control server appropriate
   to own its signaling protocol, allowing a single DHCP server to
   support multiple homogeneous call control servers as well as
   heterogeneous telephony and gateway devices.

4. References

   [1] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
       Extensions", RFC-2132, March 1997.

   [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement
       Levels", RFC-2119, March 1997.

   [3] Droms, R., "Dynamic Host Configuration Protocol", RFC-2131,
       March 1997.

5. Security Considerations

   DHCP currently provides no authentication or security mechanisms.
   Potential exposures to attack are discussed in section 7 of the DHCP
   protocol specification [3]. In particular, these DHCP options allow
   an unauthorized DHCP server to misdirect a telephone or gateway
   host to an unauthorized call control server.

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Internet Draft   DHCP Option for Call Control Servers      November 1998

6. Author's Address

   Henry Houh   
   NBX Corporation
   100 Brickstone Square
   Andover, MA  01810

   Phone: +1 978 740 0000 x257

   EMail: [email-masked]

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