In this paper I was trying to give as much as information about IP-PBX. By reading this paper one can easily understand ...
NORTH SOUTH UNIVERSITY Department of Computer Science & Engineering
Term Paper on IP PBX
Prepared For Dr. Mashiur Rahman Assistant Professor Department of Computer Science & Engineering
Prepared By Md. Murtoza Ali Quader (shadman) ETE-405 ID - 061213045 1
Abstract In this paper I was trying to give as much as information about IP-PBX. By reading this paper one can easily understand what is IP-PBX, what is the benefit of it. And how easily one can setup his own IP-PBX system. In this paper I give details information about how one can setup IP-PBX system, from where you can buy the hardware & software necessary for setting up an IP-PBX system. And what is the future, advantages and current market of IP-PBX system.
Table of Content
1. Introduction ---------------------------------------------------------------------------------- 4 2. IP PBX Rapid Growth and Implications ------------------------------------------------ 6 3. System/Protocol Architecture ----------------------------------------------------------- 8 4. Advantages of IP PBX --------------------------------------------------------------------- 10 5. Some Standards Used in IP PBX Software -------------------------------------------- 12 6. IP PBX Interface Selection Guide (Asterisk Hardware) ---------------------------- 13 7. IP PBX Software ---------------------------------------------------------------------------- 14 8. Main types of interface on an IP PBX ------------------------------------------------- 14 9. Security of IP PBX ------------------------------------------------------------------------- 15 10. Firewall Options ---------------------------------------------------------------------------- 17 11. IP PBX Security Service Provider -------------------------------------------------------- 17 12. Feature of IP PBX --------------------------------------------------------------------------- 17 13. The reasons of using OpenSource based IP PBX ------------------------------------- 20 14. Conclusion ----------------------------------------------------------------------------------- 21
Introduction PBX is actually an acronym for the term Private Branch Exchange. A Private Branch Exchange (PBX) is a telephone exchange that operates a local business or office‘s telephony service. In other words, a PBX is the technical term for a phone system. A PBX is used to make connections among the internal telephones of a private organization. Utilizing a PBX a company can save considerable cost savings on internal phone calls. PBX systems handle the circuit switching locally reducing chargers for local phone service. Another advantage of utilizing a PBX phone system is that it allows a company to share trunk lines (external lines) for all its employees, maximizing usage of dedicated phone lines. 
IP stands for Internet Protocol, a signal and data transfer technology that is used by your Local Area Network (LAN) and the internet. Typical IP PBX phone systems can switch calls between a VoIP user and a traditional telephone user, in the same way a traditional PBX system works. Replacing traditional PBX systems, IP PBX allows calls to be sent via data packets over a data network instead of the traditional phone network. The real advantage of an IP PBX or a VoIP PBX is that it utilizes a single network for both voice and data. With a IP PBX you would require a separate network for voice and data communications. This means that internet access and traditional voice communications are possible using a single line to each user.
IP PBX integrates into the network 4
An IP PBX handles voice signals under Internet protocol, bringing benefits for computer telephony integration (CTI). An IP-PBX can exist as physical hardware, or can carry out it function virtually, performing the call-routing activities of the traditional PBX or key system as a software system. The virtual version is also called a "Soft PBX". The traditional PBX based on the TDM technology is reaching the end of its lifecycle due to the emergence of IP-PBX. The IP-PBX, based on the VoIP technologies, offers easier user administration and advanced applications. With an IP-PBX, the Local Area Network is the platform for connecting smart IP phones logically over a shared packet network to the call manager. Enterprises don‘t need to disrupt their current external communication infrastructure and operations. With IP PBX deployed, an enterprise can even keep its regular telephone numbers. This way, the IP PBX switches local calls over the data network inside the enterprise and allows all users to share the same external phone lines.
IP PBXs Rapid Growth and Implications IP PBXs are well on their way to becoming the primary type of premises-based voice systems – particularly in the large enterprise market space. In publicly available research, a recent Dell'Oro Group report reveals that large IP PBX systems registered 17 percent growth in Q205 to become a $367 million industry. The report also disclosed that nearly 34 percent of total large PBX line shipments worldwide are IP PBX lines, almost double from only 16 percent the previous year. Infonetics reports that ―Worldwide, IP PBX annual revenue reached $256 million in 2003 and is predicted rise to $830 million in 2007,‖ and ―while traditional PBX line shipments will decline by a 15.4% CAGR over this period, shipments of converged PBX lines are expected to grow at an 11.2% CAGR. Pure IP PBX line shipments are expected to grow even more dramatically, at a 28.9% CAGR‖.
The growth in IP PBX shipments, however, masks the true use of IP-based telephony in enterprise environments. In fact, a recent report from BCR states that, ―Based on system design and optional capabilities, almost all new PBXs now shipping can be classified as IP telephony systems -- i.e., they can support IP endpoints and/or use a LAN/WAN infrastructure for transmission and switching among port carriers or endpoints.‖ This same report identifies that of the 7.75 million PBX station shipments in 2004, roughly 3 million were for IP station sets, with the expectation that 80% of all station sets will be IP based by 2009. Though station shipments seem to be closely correlated with new systems, a great percentage of these stations are being shipped to customers with existing PBX systems. In these cases, recent vintage, TDM (time division multiplexed or circuit-based) PBXs are able to provide Voice over IP (VoIP) functionality by a fairly simple integration of IP cards and software in their chassis. Such PBXs are often called ―hybrids‖.
There are mainly four factors that are driving acceptance of IP PBX. These are: • Falling prices for IP phones and media gateways. • Increasing number of customer LAN/WANs capable of supporting quality of service (QOS) requirements for real-time voice. • Improved system design to meet customer needs such as remote location support; improved survivability; and new disaster recovery options. • General market acceptance of the technology platform as risk-acceptable.
. Glenn LeBrun, Sr. Product Marketing Manager, GENBAND . Business Communications Review, January 2005, (http://www.bcr.com/bcrmag/2005/01/p38.php)
According to the figure shown above an IP-PBX system compare with additional software (Cisco call manager), PSTN Gateway, Media Server, IP Phone, Soft phone, PDA soft Phone, & VoIP Firewall. Usually an IP phone connects to a LAN either through a hub port or a switch port. The phone can talk with CallManager and registers itself. CallManager stores the IP-address-to-phone-number mapping (and vice versa) in its tables. When a user wants to call another user, the user keys in the called party's phone number. The Call Manager translates the phone number to an IP address and generates an IP packet version of ring tone to the called IP phone through the TCP connection. When the called IP phone receives the packet, it generates a ring tone. When the user picks up the phone, CallManager instructs the called IP phone to start talking with the calling party and removes itself from the loop. From this point on, the call goes between the two IP phones. When any change occurs during the call due to a feature being pressed on one of the 8
phones, or one of the users hanging up or pressing the flash button, the information goes to CallManager through the control channel. If a call is made to a number outside of the IP PBX network, CallManager routes the call to an analog or digital trunk gateway which in turn routes it to the PSTN. Now you may ask what CallManager is. CallManager is a member of a class of systems called softswitches. In a softswitch-based system, the call signaling components and device controllers are not separated by a hardware bus running a proprietary protocol, but instead are separate boxes connected over an IP network and talking through open and standards-based protocols. CallManager provides the overall framework for communication within the corporate enterprise environment. CallManager handles the signaling for calls within the network and calls that originate or terminate outside the enterprise network. In addition to call signaling, CallManager provides call feature capabilities, the capability for voice mail interaction, and an application programming interface (API) for applications. As you can see an IP PBX network also consist of many different endpoint devices. These devices can be classified into the following categories: • Station devices—Station devices are generally telephone handsets. CallManager offers four different types of handsets, which it controls with Skinny Protocol. • Gateway devices—Gateway devices provide access from one telephone system to another. This access can be from one network of CallManager servers to another, from a CallManager network to a PBX, or from a CallManager network to a public network • Media Server---Media Server is located in the service provider‘s network. It is also referred to as an announcement server. For voice services, it uses a control protocol, such as H.248 (Megaco) or MGCP, under the control of the call agent or application server. • IP Phone/PBX---IP Phones and PBX systems are located at customer premises and provide voice services. They interact with the Call Agent/SIP Server using a signaling protocol such as SIP, H.323 or a device control protocol such as H.248 (Megaco) or MGCP. • Soft Phone---In computing, a softphone is a software program for making telephone calls over the Internet using a general purpose computer, rather than using dedicated hardware. • ATA (Analog Terminal Adapter) ---Connects an Analogue Telephone to a VOIP network usually has an Ethernet jack, and an RJ-11 phone jack.
. Cisco CallManager Architecture
Advantages of IP PBX 1. Much easier to install & configure than a proprietary: An IP PBX runs as software on a computer and can leverage the advanced processing power of the computer and user interface as well as Windows‘ features. Anyone proficient in networking and computers can install and maintain an IP PBX. By contrast a proprietary phone system often requires an installer trained on that particular proprietary system. 2. Easier to manage because of web/GUI based configuration interface: An IP PBX can be managed via a web-based configuration interface or a GUI, allowing you to easily maintain and fine tune your phone system. Proprietary phone systems have difficult-touse interfaces which are often designed to be used only by the phone technicians. 3. Significant cost savings using VOIP providers: With an IP PBX you can easily use a VOIP service provider for long distance and international calls. The monthly savings are significant. If you have branch offices, you can easily connect phone systems between branches and make free phone calls. 4. Eliminate phone wiring: An IP Telephone system allows you to connect hardware phones directly to a standard computer network port (which it can share with the adjacent computer). Software phones can be installed directly onto the PC. You can now eliminate 10
the phone wiring and make adding or moving of extensions much easier. In new offices you can completely eliminate the extra ports to be used by the office phone system. 5. Eliminate vendor lock in: IP PBXs are based on the open SIP standard. You can now mix and match any SIP hardware or software phone with any SIP-based IP PBX, PSTN Gateway or VOIP provider. In contrast, a proprietary phone system often requires proprietary phones to use advanced features, and proprietary extension modules to add features. 6. Scalable: Proprietary systems are easy to outgrow: Adding more phone lines or extensions often requires expensive hardware modules. In some cases you need an entirely new phone system. Not so with an IP PBX: a standard computer can easily handle a large number of phone lines and extensions – just add more phones to your network to expand. 7. Better customer service & productivity: With an IP PBX you can deliver better customer service and better productivity: Since the IP telephone system is now computerbased you can integrate phone functions with business applications. For example: Bring up the customer record of the caller automatically when you receive his/her call, dramatically improving customer service and cutting cost by reducing time spent on each caller. Outbound calls can be placed directly from Outlook, removing the need for the user to type in the phone number. 8. Twice the phone system features for half the price: Since an IP PBX is softwarebased, it is easier for developers to add and improve feature sets. Most VOIP phone systems come with a rich feature set, including auto attendant, voice mail, ring groups, advanced reporting and more. These options are often very expensive in proprietary systems. 9. Allow hot desking & roaming: Hot desking – the process of being able to easily move offices/desks based on the task at hand, has become very popular. Unfortunately traditional PBXs require extensions to be re-patched to the new location. With an IP PBX the user simply takes his phone to his new desk – No patching required. 10. Better phone usability: SIP phones are easier to use: Employees often struggle using advanced phone features: Setting up a conference, transferring a call – On an old PBX it all requires instruction. Not so with an IP PBX – all features are easily performed from a user friendly Windows GUI. In addition, users get a better overview of the status of other extensions and of inbound lines and call queues via the IP PBX Windows client. Proprietary systems often require expensive ‗system‘ phones to get an idea what is going on your phone system. Even then, status information is cryptic at best.
Some Standards Used in IP PBX Software  -G.711: an international standard used for encoding (packetizing) telephone voice at either 56kbs or 64 kbps - this is uncompressed digitized voice. -G.723: a protocol for compressing voice to 6.4 kbs or 5.3 kbs. The compression quality is very good with voice quality as good as normal telephone voice quality. It is supported by virtually all IP telephone equipment. -H.323: Signaling & telephone services protocol for the transmission of IP packets representing any combination of voice, video and data. H.323 is designed for operation over existing IP networks. Includes facilities call setup signaling and media control. Allows VoIP equipment to interoperate. -SIP (Session Initiation Protocol): A signaling & telephone services protocol similar to, but simpler than, H.323.
IP PBX Interface Selection Guide (Asterisk Hardware) Because voice over IP is digital, often a standard PC or server is used for the PBX. Those VoIP PBX's (aka IP PBX) need PCI interface cards to connect to analog telephone lines, digital T1/E1 lines, analog telephone handsets and fax machines. This category contains PCI interface cards from the leading manufacturers in the industry. If you are using Asterisk IP PBX or a variant such as trixbox, Elastix, AsteriskNOW, FreePBX and need to connect it to something, this guide will help you to select the best one. According to my survey I found these devices are best. Sangoma Connectivity Hardware Sangoma interface cards allow you to connect voice over IP PBX's to T1/E1services, analog telephone lines, analog telephones and fax machines. Sangoma offers optional hardware echo cancellation on most of their cards and all cards carry a Lifetime Manufacturer Warranty.
Rhino Equipment Rhino's high quality - made in America interface cards allow you to connect your IP PBX to T1/E1 services, analog telephone lines, analog telephones and fax machines Optional hardware echo cancellation is available of many of their cards.
Redfone T1/E1 HA Interfaces RedFone's solid state T1/E1 interface adapters are designed to provide high availability solutions for trixbox/Asterisk based solutions.
Digium Analog & Digital Interfaces Digium, the creators of the Asterisk IP PBX software offer their own line of interface cards to connect your IP PBX's to T1/E1services, analog telephone lines, analog telephones and fax machines. Optional hardware echo cancellation is available on some of their cards.
OpenVox Cards OpenVox has a wide selection of budgetconscious interface cards with FXS/FXO ports and T1 / E1 ports for most IP PBX's. Connect your IP PBX to analog telephones, fax machines and analog telephone lines. OpenVox's A400M series is a great option for small, low power IP PBX's.
Xorcom USB Asterisk Channel Banks Xorcom's innovative channels banks deliver FXO, FXS, T1/E1 connections to your IP PBX system over USB 2.0 eliminating the need for available PCI slots.
Dialogic / Eicon Diva Cards Dialogic offers a range of enterprise grade telephony interface cards designed specifically for large scale implementations and high reliability systems.
IP PBX Software There are many software for IP PBX. According to my survey the following are the most used software. -
Asterisk: Asterisk is the most popular open source IP PBX in the world. Many variations of Asterisk are now available such as trixbox, AsteriskNOW, and elastix that can provide advantages and disadvantages over the original Asterisk. These IP PBX's can be loaded on to personal computers or business servers to build a feature rich, business grade voice over IP phone system.
4S IP PBX: The 4S IP PBX is a product package based on the 4S proxy and the 4S media server. It allows users to migrate from traditional PBX-based telecommunication systems to modern service-oriented VoIP technology. This software provides the complete set of functions users expect from traditional PBX devices and more.
Dial-Office IP-PBX: Dialexia's line of enterprise solutions is a suite of products that address small business communications needs. For companies that have an established Local Area Network (LAN), Dial-Office is the ideal IP based PBX solution. This IP PBX system is a full featured PC-based IP Communication Server designed specifically for the rapidly emerging voice over IP and data convergence market.
Main types of interfaces on an IP PBX There are four main types of interfaces on an IP PBX, FXS, FXO, T1/E1 and Ethernet. An FXS interface is used to connect analog telephones or faxes to the IP PBX. An FXO interface is used to connect analog telephone lines to the IP PBX. A T1/E1 interface is used to connect the IP PBX to high speed, ultra-reliable internet connections. Ethernet interfaces are used to connect an IP PBX to the local area network (LAN). 14
T1/E1: Highly reliable digital data connection. Some VoIP providers can install a T1/E1 circuit to deliver phone calls to your IP PBX system. T1 is the US standard and E1 is the European standard. If you have a VoIP connection delivered over a T1, you do not need any telephone circuit interface equipment. PRI (Primary Rate Interface): A PRI is a telephony circuit that is delivered over a T1/E1 circuit, this is the industry standard for delivering voice phone calls to business customers. Over a T1 you will get 24 simultaneous calls and an E1 will get you 30 simultaneous calls. You will need a T1/E1 interface card to use these types of circuits. FXO: Analog telephone line connection (POTS) - 1 call per port - An FXO connection connects to an analog telephone line jack. FXS: Analog telephone or fax machine connection - 1 device per port.
Security of IP PBX The current crop of VoIP PBX systems provides an IP-based alternative to traditional circuitswitched phone systems, delivering savings and flexibility for enterprises of all sizes. Like any IP-based system, however, a VoIP PBX brings with it risks that can't be ignored--among them, denial-of-service attacks, privacy breaches, and theft of services. Securing a VoIP PBX presents some unique challenges, but the alternative--loss of service and, possibly, loss of customers--may be more costly in the long run. Fortunately, safeguarding an IP PBX doesn't require an army of experts or Big Brother-style intrusions. You can get off to a good start by applying the same basic principles you'd use with any IP-based system: Adopt a defense-in-depth strategy to protect components of your PBX from as many threats as possible. Consider your network infrastructure as well as your phones. How many VoIP phones have you deployed? How big is your network? These calculations will help determine what steps to take next. Isolating components on virtual LANs is a popular approach for securing the corporate network. Many VoIP phones, including those from Polycom and Grandstream Networks, have built-in switches that set up an 802.1p/Q trunk over the link to the local switch in the wiring closet. 802.1p/Q allows VLANs to share a physical network without leaking information. The trunk separates voice traffic from data traffic, from the phone all the way to the IP PBX. Isolating VoIP traffic will boost security, but it won't stop all intruders. Software that mimics the VoIP VLAN could let an attacker tap in from a data jack. You can limit the UDP and TCP ports that can access the IP PBX from the VLAN by using the access control lists on switches or 15
routers or by installing a firewall to limit the TCP and UDP ports that are vulnerable. You can also lock down the Ethernet addresses that access the network. Defining separate VLANs for phones also makes it possible to better control bandwidth allocation--in other words, raise quality of service--to protect the IP PBX from denial-of-service worms that originate on the network. VoIP doesn't require much bandwidth, but it's sensitive to packet loss and delays, so boosting quality of service can be very effective in keeping conversations going during such an attack. You also need to be careful with auto configuration protocols, such as the LLDP-MED standard or Cisco's proprietary CDP. These protocols ease the administrative burden of VoIP phones and VLAN configuration, but they aren't hard to spoof. VoIP phones' use of encryption today provides better privacy protection than most legacy phones. However, protection only lasts until a call leaves your network. The public switched telephone network doesn't provide encryption. The signaling protocol for outgoing calls can be encrypted, as can the Real-Time Transport protocol that transports the actual conversation. Encrypting the signaling protocol will prevent eavesdroppers from gleaning phone numbers within your organization.
VoIP phones have a built-in switch that creates an 802.1p/Q trunk over the link to the local switch in the wiring closet. The 802.1p/Q-enabled link separates voice and PC data onto distinct VLANs, so one cable can carry both types through the company network. The VLANs carry traffic to the data center switch, which sends voice data to the IP PBX and other data to its network destination.
Firewall rules should deny all Internet access to your IP PBX servers, gateways, and phones, and should limit access between the phone VLAN and IP PBX. Vendors such as Check Point say they can do this via Session Initiation Protocol filtering, but there may be compatibility issues. Test this feature carefully with your equipment. You may also want to consider a Session Border Controller. Offered by vendors such as Ingate, SBCs analyze traffic patterns to protect networks from SIP-based denial-of-service attacks. Using VPNs for Internet access is a logical way to accommodate telecommuters, but if you're using soft phones and the VPN becomes compromised, that could compromise your phone system as well. Also, if there's already high latency on the connection, a VPN could put it over the edge.
IP PBX Security Service Provider According to my survey following are widely used IP PBX security service provider. 1. 3CX VoIP Security Solution. (http://www.3cx.com/) 2. The Sipera VoIP/UC Security Solution. (http://www.sipera.com/) 3. Interactive Intelligence. (http://www.tmcnet.com)
Feature of IP PBX 
Unlimited Extensions Unlimited Auto Attendants Unlimited Voicemail Boxes Cell Phone Integration Integrated Paging Remote Phones Advanced User Interface (including Find me/Follow Me, Unified Messaging, Call recordings, Voicemail .wav). Extension Groups Auto Provisioning Extension Range Flexibility Caller ID Customization DID Direct Inward Dialing Find Me/Follow Me Time of Day Routing Extension Call Recording 17
On the Fly Recording Call Return Voicemail Callback Voicemail to Email SMS Voicemail notification Voicemail Web Access Voicemail Bypass Intuitive VoIP Ready Voicemail Blast Groups VoIP Ready Inbound Call Description VoIP Compression Outlook Integration Announcement Interface Call Out Call Pickup System Diagnositcs Multivendor Phone Options Analog Phone Support BYO Phones Call Parking Call Barge Dial by Name Directory Powerful Reporting CRM Integration Remote Linked Servers Operator Console Custom Routing Rules Conference Rooms Outbound Dial Map Speed Dial Numbers Channel Bank Support Multiple Music on Hold Analog and Digital T1 Ready PSTN or Digital Failover NIS Routing Advanced Routing (IVR) Fast Pass Caller Position Notification Call Whisper Auto call forwarding Unified Messaging Call Screening ANI Routing DNIS Routing 18
Enhanced Mobility Overhead Paging Custom VoIP Provider Professional Development Fax Support Fax to Email Fax PDF Support ACD Features Click to Dial Softphone Call Transfer call Conference Live Monitoring
The reasons of using OpenSource based IP PBX 1. Avoid Costly Telephone Wiring. 2. Twice the phone system features for half the price! 3. Forward VoiceMail to your email inbox. 4. Increase productivity of Your Employees by integrating phone System with CRM, ERP and Outlook Express. 5. Linking office Locations: Make free video and voice calls between your office branches 6. Zero License fee. 7. Allow Hot Desking and Roaming. 8. Teleworking: Soft phone can be installed in your employee‘s laptops. 9. Scalable: Grow with your business! 10. Significant cost savings using VOIP providers of your choice.
Asterisk-based OpenSource telephony Systems offer a rich and flexible feature set. Asterisk offers both traditional PBX functionality and advanced features, and interoperates with traditional standards based telephony systems and Voice over IP systems. Asterisk offers the features one would expect of a large proprietary PBX system such as Voicemail, Conference Bridging, Call Queuing, Call Recording, and Call Detail Records. So we can use this system very easily and the future is very bright for IP PBX.
Conclusion With the explosion of IP PBXs and IP PBX hybrids into the enterprise market space, service providers need to step up to the next level of service for these customers. Using the G6 Trunking Gateway to provide the IP PBX Network Trunking solution, service providers can now create true savings for IP PBX customers by allowing their voice traffic to access the service provider‘s IP network. Such access will require two main elements: 1) a policing and interworking entity, given the nature and risk in the enterprises‘ private IP networks, and the SIP Proxy Server provides this function; and 2) a highly reliable, highly scalable trunking gateway that can accept SIP signaling from the Proxy Server and convert both bearer and signaling traffic between the IP and TDM networks, and the G6 Trunking Gateway feature provides this function. Because this functionality is new, yet vitally important to IP PBX customers, service providers should deploy this solution as rapidly as possible in their networks to ensure that they step up to the next level of service for these important and profitable customers – before somebody else does.