A Guide to SIP Phone Numbers: Hardware and Software Requirements

The Session Initiation Protocol (SIP) is a signaling communications protocol, widely used for controlling multimedia communication sessions such as voice and video calls over Internet Protocol (IP) networks. SIP can be more flexible because it works independently of the type of session or media used. SIP is designed to support the calling features of traditional telephone systems. However, unlike the traditional technology for telephone signaling, SIP is a peer-to-peer protocol. SIP is also a general-purpose protocol for multimedia communications not limited to voice applications.

Basic Building Blocks of a SIP-enabled Enterprise

When you are ready to enhance your enterprise communications with SIP but do not have a dedicated IT departments, begin by understanding the basic building blocks that form the foundation of your new SIP-enabled enterprise: user agents and SIP servers.

• User agents (UAs) - applications installed on SIP endpoints, such as an IP phone, mobile phone, wireless device or PDA, or a laptop or desktop PC that interface between the user and the SIP network.
• SIP servers - SIP servers provide centralized information and enablement services in a SIP ecosystem.
• Registrar Server - authenticates and registers users when they come online signalling to others that they’re available to take and make calls.
• Location Service - a database that keeps track of users and their locations.
• Redirect Server - redirects SIP requests to users that are not in their home domains.
• Proxy Server - establishes sessions by processing SIP requests and passing them downstream while sending responses upstream to other SIP servers or devices.
• Presence Server - accepts, stores, and distributes presence information that allows users to see the availability of people they want to contact.

Critical Components of an SIP Trunking Solution

Several components are needed to set up a SIP trunking solution: a broadband connection, SIP-enabled devices, a PBX (Private Branch eXchange or Private Business eXchange), an edge device that can handle the traversal of SIP traffic and a SIP trunk from an ITSP.

• A broadband connection - the more simultaneous users you have, the more bandwidth you will need. Make sure that your internal network—including your routers and switches—can handle the load, too.
• SIP-enabled phones - even if you subscribe to a cloud-based hosted VoIP service, you'll need to make sure your phones can communicate over VoIP
• The PBX component - a telephony exchange serving an enterprise or organization office. There are several different types of PBXs available on the market.
• The enterprise edge component - The enterprise edge component can either be a firewall with complete support for SIP or an edge device connected to the firewall, handling the traversal of the SIP traffic.
• The service provider component - A traditional voice telephony service provider typically offers one or more T1/E1 trunks to the enterprise for fulfilling its needs for voice communication outside its own premises.

Typically, the service provider will have solutions for your software needs including free mobile applications and a desktop client with plug-in-based integration for several services and programs, including Outlook, Microsoft Dynamics, SugarCRM, and LinkedIn. The service provider can also help identify any missing hardware components you might need as well as how to acquire them.