2003 February

February 2003

Read this white paper from Microsoft – it describes the RTC Platform and the base protocols: SIP, RTP, SIMPLE.

This paper is written for IT professionals and developers interested in understanding the concepts, protocols, and technologies of real-time communications. It describes protocols such as the Internet Engineering Task Force (IETF) Session Initiation Protocol (SIP), SIP Instant Messaging and Presence Language Extensions (SIMPLE), and Real-time Transport Protocol (RTP). Microsoft uses these protocols and related technologies to provide a real-time communications (RTC) platform for corporate multi-modal communication, which includes voice and video communication, instant messaging, application sharing, and collaboration. Throughout this paper, voice communication and the way the Microsoft Windows XP operating system supports it are used to illustrate how the underlying technologies work.

We need a new URI for Internet Telephony. Here\’s a draft specification of the enum: URI:

This URI is intended for use where a resource address can be returned by evaluating the URI value using the ENUM DDDS application. Syntactically, it uses a subset of the format defined for the \”tel:\” URI scheme.

The tel: URI is specified in RFC2806bis . This holds a telephone number and optional parameters. It can be used to initiate a telephone call to the number it holds as its value, or may be used within a SIP session setup (e.g. it may be used in the from: or to: fields of a SIP Invite message; see RFC3261 for more details). The \”tel:\” URI does not specify whether or not an ENUM query should be made prior to initiating a call; thus a \”tel:\” client may or may not generate a request to the ENUM infrastructure. It is convenient to have a URI that appears very similar in format to the \”tel:\” URI, but with which a compliant client MUST generate a query on the ENUM system. That is the role for the \”enum:\” URI scheme, as specified in this document.

A new draft outlines an ENUM service definition for SIP: urls:

ENUM (E.164 Number Mapping, RFC2916bis) is a system that transforms E.164 numbers into domain names and then uses DNS (Domain Name Service, RFC1034) services like delegation through NS records and NAPTR records to look up what services are available for a specific domain name.
This document registers a group of \’enumservices\’ to be used to
indicate that the associated resources are capable of interactive
media stream exchange.

Specifically, the \”enumservices\” registered with this document are
\’voice\’ and \’video\’ using the URI schemes \’sip:\’, \’h323:\’ and

A new draft covers a SIP management system based on the Diameter framework:

This document specifies a Diameter application that supports the authentication, authorization, and collection of accounting information for Session Initiation Protocol (SIP) services rendered to a client node. This application, combined with the base Diameter protocol and appropriate SIP extensions, allows SIP User Agents (UAs) to obtain services from SIP servers that are connected to a Diameter infrastructure. When combined with the Inter-Domain capability of the base protocol, service may even be obtained from SIP servers that belong to foreign domains, as would be encountered by roaming mobile nodes.

Cert today published a report on security problems in a number of SIP implementations. The report is based on work done in Finland:

Numerous vulnerabilities have been reported in multiple vendors\’ implementations of the Session Initiation Protocol. These vulnerabilities may allow an attacker to gain unauthorized privileged access, cause denial-of-service attacks, or cause unstable system behavior. If your site uses SIP-enabled products in any capacity, the CERT/CC encourages you to read this advisory and follow the advice provided in the Solution section below.

Clavister responds to the CERT report that
\”We would also like to reiterate the fact that SIP has yet to mature, protocol-wise as well as implementation-wise. We do not recommend that our customers set up SIP relays in parallel to our firewall products to pass SIP-based applications in or out of networks where security is a concern of note.\”

A lot of information on ENUM today. ENUM will change the world and lead the way to proper convergence of telephony and the internet.

A lot of visionary visdom in one sentence, but I do believe ENUM will make a difference. Again, depending on the model. In the classic telephony model, the telco owned the phone number and the directory entry. Now, phone numbers are getting telco independent. Next, we will have control of the phone number ourselves with ENUM. At least, in my mind. I want to choose which telco to route my phone calls to, if I want to route them to a telco at all.

VISIONng (http://www.visionng.org) announced today that a US trial of ENUM, an Internet Standard which uses the Internet Domain Name System (DNS) to reconcile telephone numbers, will be deployed for use with the Global Country Code \”87810.\”
An affiliated company to pulver.com\’s Free World Dial-up service will become an ENUM registrar enabling Free World Dialup (FWD) participants to maintain an ENUM entry that will enable a universal service. The use of the \”87810\” can also be used for vanity numbers, particularly for people who want to associate their Voice over IP (VoIP) gateways at home to their existing United States \”1+\” phone numbers.

Read, learn and think about it for a while. Isn\’t ENUM amazing? The real question is who will be in control of an entry – you or your phone operator?

Enum Forum recently released a US agreement regarding the implementation of ENUM:

ENUM allows the use of traditional phone numbers, as used around the world today, as a method for placing telephone calls and other services over an IP infrastructure. The ENUM Forum Recommendation lays out the fundamental structure for Tier 1 service, Registrar functionality as well as guidelines for the Tier 2 providers.

“The release of the Specifications has brought the implementation of ENUM in the United States one step closer to becoming reality” stated Gary Richenaker, who serves as the Chairman of the ENUM Forum. “The forum membership has produced a well thought out document which has undergone deep consideration by members in the telecommunications and Internet industries”.

Newsfactor network writes about VOIP and WLAN, one of my favourite subjects:

A number of manufacturers, including HP, see voice over WLAN Latest News about WLAN technology Relevant Products/Services from CIO Today Magazine as an ideal way for firms to test voice over IP (VoIP) before extending it to wired networks. In the meantime, vendors are developing suitable access points, wireless gateways and telephony applications based on existing 802.11 WLAN standards.

\”Integrating voice over WLAN, security and convergence applications together might be the trigger for taking VoIP into the mainstream. This will provide corporates with the ability to untie the desktop phone from the desktop,\” said John McHugh, HP\’s UK vice president and general manager.

Next Page »