Remote Administration via DLS within NAT environments (DCMP)

Systematics
Family:	OpenStage
Model:	OpenStage 15 OpenStage 20 OpenStage 40 OpenStage 60 OpenStage 80
Relation:	SIP related
Release:	V2 R0

This feature enhances the existing OpenStage phone’s DLS interface by providing a means for the OpenStage SIP Phone to make use of a DLS Server which is deployed behind a Firewall/NAT. Supporting DLS usage in NATed environments like hosted HiPath 8000 environment, a DLS Contact Me Proxy (DCMP) was introduced with optiPoint SIP phones. This feature is now also available for OpenStage SIP Phones.

A detailed description can be found in the updated OpenWPI documentation for V2 R0

Solution Overview

To solve the Firewall/Nat traversal problems a DLS Contact-Me Proxy (DCMP) is deployed on a server in the same DMZ / location as the DLS server and has similar requirements to the connectivity as the XML-message part of the DLS Interface:

• Allow incoming HTTP requests from any location where devices are installed that need to con-tact the DLS.

Devices that suffer from the problems described in the preceding chapters, need to be configured to poll the DCMP periodically by issuing an HTTP request that determines whether DLS needs to be con-tacted or not:

Solution: DLS Contact-Me Proxy (DCMP)

The device polls the DCMP using a HTTP Request sent to the dcmp-url, which is obtained from the DLS. The device adds the parameter

contact-me?device-id=<mac-addr> 

to the URL where <mac-addr> is the Device ID as registered to DLS (item mac-addr).

For example:

http://dcmp-server:8080/dcmp/contact-me?device-id=0A:E8:F3:00:42:91

The decision criterion for the device is the HTTP return status code. The possible values are:

• 200 OK – No pending DLS jobs, a DLS session does not need to be opened
• 202 ACCEPTED – Pending DLS jobs available, the device should open a DLS session using the ReasonForContact = solicited

Two parameters are required for that purpose and can be set by DLS individually per device:

• the DCMP URL to be called
• the poll interval

Device Requirements

• Configuration of DCMP URL and poll interval via DLS. Note: the Contact-Me is still mandatory and to be supported in any case (and always active, independent of the device's DCMP configuration). Their current value need not to be stored persistently on the device: every restart of the device leads to a startup-request to DLS, where the current valid settings of these items are obtained.
• Execute poll requests at the required interval (in addition to listening on contact-me) and check HTTP return status code. The status code 202 ACCEPTED indicates that pending DLS jobs are available. The device should open a DLS session using the ReasonForContact = solicited. Note: Any contact to DLS (e.g. due to device start-up, local-changes, inventory-changes, etc.) should restart the timer for the DCMP poll interval

Data

dcmp-enable

Determines whether the OpenStage device will attempt to use thd DCMP procedures (i.e. contact the proxy at the address determined by the dcmp-url.

OCMS tag	dcmp-enable
New	Yes
Type	Boolean
Default	false
Profile	Device
Access	None (This data item is downloaded from DLS and not persisted on the device)
DLS/XML	Yes
Menu	No
WBM	No
Lockdown	No
User backup	No

dcmp-url

The URL of the DLS Contact Me Proxy.

OCMS tag	dcmp-url
New	Yes
Type	Boolean
Default	Null
Profile	Device
Access	None (This data item is downloaded from DLS and not persisted on the device)
DLS/XML	Yes
Menu	No
WBM	No
Lockdown	No
User backup	No

dcmp-interval

The URL of the DLS Contact Me Proxy.

OCMS tag	dcmp-interval
New	Yes
Type	Boolean
Default	Zero
Profile	Device
Access	None (This data item is downloaded from DLS and not persisted on the device)
DLS/XML	Yes
Menu	No
WBM	No
Lockdown	No
User backup	No