Allstream Converged IP Telephony SIP Trunking Solution An Allstream White Paper 1
Table of contents Introduction 1 Traditional trunking: a quick overview 1 SIP trunking: a quick overview 1 Why SIP trunking? 1 Allstream SIP Trunking: an overview 2 Trunking design considerations 2 Design challenges of TDM trunking 2 Design advantages of SIP trunking 3 WAN considerations for SIP trunking 4 SIP trunking migration scenarios 5 Ensuring interoperability 5 Conclusion 6 About Allstream 7
Introduction Over the past decade, organizations of all sizes, in all sectors, have been driven to achieve two critical goals: to cut costs while enabling new technologies. To meet these equally compelling and apparently contradictory objectives, a growing number of businesses have begun to explore the benefits of IP technology. Yet, while IP deployments proliferate, many organizations still continue to maintain multiple PRI (Primary Rate Interface) facilities when connecting to the PSTN a configuration that results in added costs and more complex management. SIP trunking helps avoid these challenges by enabling organizations to consolidate their voice and data traffic onto a single transport and a single provider. This paper is designed to help IT professionals and telecom managers learn more about this technology and its benefits and design alternatives, so you can make an informed decision when moving to SIP trunking. Traditional trunking: a quick overview Today, most businesses run standard PBX or key systems supplemented by trunk side access services purchased from traditional telephony providers (also known as TDM trunking). T1, PRI, BRI and analog lines typically handle voice traffic to and from the PSTN. These circuits are channelized and carry a maximum of 24 simultaneous calls. While these businesses also maintain Internet connections and data networks, these tend to be separate from their voice connections. SIP trunking: a quick overview SIP trunking allows an enterprise to virtually connect an IP PBX to the PSTN via a service provider IP access circuit. As a result, the enterprise no longer needs traditional PSTN circuits such as T1 and PRIs. This one IP pipe also can handle any communications need, including: IP telephony (VoIP) to the PSTN enterprise interoffice voice communication data and Internet traffic Why SIP trunking? As the separation inherent in traditional trunking erodes, many enterprises are switching to IP telephony and deploying SIPbased IP PBX and softswitch technology. In addition to reducing the administrative and maintenance costs of running several legacy systems, this transition makes the infrastructure more efficient by enabling organizations to maintain a centralized data centre and run voice and data on the same LAN infrastructure. Thanks to this design, companies can unify their voice traffic from remote locations to eliminate long distance between sites, share voice overflow and automate failover. SIP trunking promises even greater ROI when an organization takes IP telephony beyond the LAN. IP telephony is the first step in achieving unified communications and its benefits, like: voice, video, IM and presence remote working WiFi mobile phone communications 1
Allstream SIP Trunking: an overview SIP Trunking Allstream s product name for SIP trunking supports both SIP and H.323 protocols with a host of features engineered to enable substantial cost savings compared to traditional PSTN circuits. As a result, it offers a range of benefits: Scalability Allstream SIP Trunking capacity can be managed and ordered on a per-session or per-connection basis rather than on a per 23 DS0 found on traditional circuits. High-compression voice codecs reduce bandwidth consumption allowing for increased capacity when needed. Accessibility Virtual presence allows customers to reach an enterprise when they dial local numbers in areas where the enterprise has no physical presence or physical connection to the customers local switch. Reliability Physical transport layer redundancy works in concert with SIP Trunking to ensure service (and mission-critical application availability) should the access or the router fail. Instantaneous failover to traditional circuits such as PRI, and call redirect to an alternate PSTN number, provide further service backup. Additionally, application layer resiliency is a multi-site/endpoint 1 (EP) feature that ensures call completion by using a priority hunt among end points when failure or traffic congestion occur. It s bolstered by load sharing or traffic balancing between endpoints. Cost savings Organizations with heavy client bases at rate centres (e.g. Vancouver 604) that are not their local rate centre (e.g. Toronto 416) can use toll bypass to make outbound calls to their clients without placing long-distance calls from their local exchange (416), reducing long distance charges. Traffic balancing Dynamic session allocation, based on traffic demand on a per rate centre basis, optimizes traffic during different peak-hours. Trunking design considerations Regardless of the size of your organization, SIP Trunking has the capacity to deliver tangible benefits. This is particularly true for larger enterprises with multiple locations that are considering transitioning from traditional TDM trunking. The key is to understand how to best make the transition from a traditional circuit-switched PBX and network to an efficient converged IP telephony solution. Design challenges of TDM trunking TDM trunking in a multisite environment can be challenging for many reasons: Lines, trunks and phone numbers are tied to rate centres and customers physical locations To obtain foreign dial tones, an enterprise must deploy an expensive physical connection to alternate rate centres and backhaul it over long distances Managing local services at multiple remote sites (for 911 and local presence) can be costly and inefficient Managing PSTN capacity is costly, since it s based on a per PRI increment (23 DS0) Legacy TDM PBXs are circuit-switched and support low-capacity and low-density line cards that do not scale to accommodate a large enterprise s network needs Calls between corporate branches are placed on either PRIs (treated as long-distance dialing) or tie trunks (also very costly depending on the distance the copper wires have to travel between tied sites) 1 The endpoint is a customer s IP PBX or session border controller or any SIP proxy. 2
Figure 1: Inefficiencies associated with TDM trunking for a multisite enterprise customer Design advantages of SIP Trunking SIP Trunking provides options an enterprise can use to address the challenges of multisite setups and virtual presence. For example: A single (IP) PBX supports unified dialing from remote locations for both inbound and outbound traffic Telephone numbers can be mapped to a customer s physical location Obtaining a foreign dial tone no longer requires a physical connection to alternate rate centres for local services and 911 Multisite businesses can manage local services from a central location Centralized CPE designs from IP-PBX vendors can be supported easily Overflow between locations can help optimize voice bandwidth Failover occurs should communication to one location be lost S IP Trunking can eliminate long distance between sites IP-to-IP calls from the LAN to the PSTN and between corporate sites occur without either the need to convert to TDM or the need to deploy expensive trunk gateways These enhancements are particularly attractive to national or regional businesses (e.g. financial and retail chains) that want to both source local and long distance services from a single vendor and centralize their network resources. 3
Figure 2: A typical design for a business with multiple locations WAN considerations for SIP Trunking SIP Trunking provides options for working with different WAN configurations, to address the challenges for businesses of different sizes, single vs. multi-site design, single or multiple transport options: Businesses with critical needs for best of class voice quality and service guarantees are encouraged to use Allstream Business IP (MPLS) network to access the PSTN through the Allstream SIP Trunking core network. Enterprises that do not use MPLS can utilize SIP trunking using internet access to carry voice traffic which is supported on Allstream internet data access as well as any ISP internet access. A major advantage using Allstream internet access is that it is directly connected to our core data network on which the SIP trunking network elements are installed and hard connected to the PSTN thus delivering excellent voice quality. Also with Allstream internet access all customers can take advantage of Class of Service (COS) settings which are managed at each end of the access, customer CPE and Allstream edge router, ensuring that voice packets are delivered on time while data traffic is queued. When using third party internet access, Class of Service settings cannot be applied. Voice quality may be impacted due to the increased number of network hops and possibility of internet congestion before reaching the Allstream core network. 4
SIP trunking migration scenarios An enterprise can choose different network designs based on the type of phone system it uses. For example, for existing TDM-based PBXs: A trunk gateway is needed to connect the phone system to traditional circuits such as PRIs and Allstream s CE with Switched Ethernet The trunk gateway typically performs the TDM-to-IP conversion and handles all SIP signaling via the Allstream SIP Trunking host An Allstream-supplied router (CE) handles both voice and data routing A site that is IP-PBX and SIP trunking ready connects to Allstream via the router By consolidating voice and data networks, organizations can reduce operating costs and migrate to a full IP telephony solution by deploying an IP PBX environment without the need to convert TDM to IP and vice versa. Figure 3: A typical hybrid configuration using both legacy TDM PBX and IP PBX Ensuring interoperability Equipment based on the SIP protocol (e.g. SIP phones and IP-PBXs) has been commercially available for several years. Now that SIP trunks have become common, telecom managers seek to ensure that their various elements work properly together. For this reason, standards like SIPconnect have become critical. SIPconnect, developed by the SIP Forum, is a set of best practices used to interface an enterprise PBX implementation with an ITSP that eliminates many incompatibilities that can 5
surface when combining equipment from different vendors in a single environment. However, most vendors are not SIPConnect compliant. That s why SIP signaling and handling of certain call events can vary from one vendor to another. To overcome this issue, Allstream established a certification lab and process in collaboration with many IP PBX/softswitch vendors to ensure interoperability between Allstream s SIP Trunking service and the type of IP PBX deployed on the network. The certification process ensures that a vendor s IP PBX is Allstream SIP Trunking ready. When their products are almost ready to ship, vendors (such as Avaya, Cisco, Interactive Intelligence, Mitel and Panasonic) announce interoperability details on their web sites. Allstream s certification lab also tests and verifies the service interoperability with any non-certified IP PBX prior to service activation. Conclusion Allstream uses its vast experience to provide businesses of various sizes with the most effective communications options available today. Increasingly, those options include SIP trunking, a technology Allstream has both adopted and helped its customers to implement. From network design to ensuring compatibility between the varying components of the network, Allstream guides businesses to technology choices tailored to their specific needs. Contact your Allstream representative to discuss your communications needs or visit our web site at www.allstream.com/siptrunking. 6
Canada s all-business communications provider Allstream is the only national communications provider working exclusively with business customers. Our focus is helping you simplify IT operations to improve productivity, maximize performance and manage costs. Our IP solutions are delivered on a fully managed, fully secure national network and backed by our industry-leading commitment to customer service: The Allstream Service Guarantee. Driven by the expertise of our 2,500 employees across Canada, we operate a 30,000 km fibre-optic network combining advanced IP connectivity, digital switching, Ethernet-featured services, and the latest security technologies. Our portfolio includes the highest-capacity voice, data and Internet connections, unified communications, and managed services, all flexibly designed for the needs of large, mid-market and small businesses. We can help you compete more profitably by converging voice and data over a single, reliable, end-to-end infrastructure that delivers exceptional quality of service between metropolitan centres. To learn more about Allstream please visit www.allstream.com 7
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