Procuring SIP trunking services helps save corporate communication costs


By: Aswin K -- Senior Research Analyst, IT Hardware and Telecom

24 August, 2017

Procuring SIP trunking services helps save corporate communication costs


Large enterprises with operations spread globally have the need to work collaboratively and this makes long distance calls critical for them. Traditionally businesses used to manage voice and data networks separately. This separation creates the need for multiple infrastructures, cabling systems, maintenance processes and subscription fees, which in turn drastically increases both capital and operational expenditures of enterprises.

A system rather an IP address which can handle a variety of communications, including voice, data and internet traffic is the need of the hour. Session Initiation Protocol (SIP) Trunking uses IP and internet technologies to converge voice and data traffic over a single network – an all-IP network. It allows businesses to connect an IP PBX to the PSTN via an IP access circuit. This eliminates the need for traditional PSTN circuits from the enterprise communications landscape. 

SIP trunking benefits for the enterprise

Lower total cost of ownership: As multinational organizations have their offices across the globe, there is significant amount of voice transport among these offices which results in higher telecom invoices. SIP trunking and best cost routing helps to cut down the costs significantly. Moving to a single platform for voice and data traffic reduces the capital expenditure during the initial stages and also in the long run. The convergence of voice and data networks also reduces the overheads required to operate and maintain two separate systems, thus decreasing the operational expenditures.

Enhanced employee productivity: Initially enterprises considered SIP trunking as means of reducing long distance bills only. However, the advancements in communication technologies made it evolve as a platform which enables sophisticated applications such as unified communications, audio and video conferencing and worker collaborations. SIP trunking allows employees to connect to all their phone numbers remotely. It also allows a single number to be registered to a variety of devices, making staffmembers available to their customers even when they are travelling.

Also it enhances the customer satisfaction through improved business processes such as ERP and CRM systems, web-based click to call, etc.

Benefits for the service provider

Single conduit for both data and voice: Large enterprises usually subscribe to an IP-based network infrastructure. By transporting voice to the same network infrastructure, telecommunication companies can drastically reduce the total cost of deploying and delivering both services.

Reduced total cost of ownership: SIP trunking helps reduce capital expenditure for service deployment using a single network to transport voice and data traffic. Implementing SIP trunking also reduces the operational complexities involved in handling the system while expanding geographically.

Capability to offer premium collaborative and conferencing tools in their cloud-based services help a service provider to differentiate themselves from competition.

Constraints for SIP trunking migration

Legacy PBX:  There is a perception among network and sourcing professionals that upgrading PBX is essential for migrating to SIP trunking. This has dissuaded enterprises from investigating SIP trunking which in turn is delaying the migration.

WAN Upgrade: Enterprise voice services need adequate WAN bandwidth and quality of service. It has now become convenient with better ethernet access and drop in the U.S. multiprotocol label switching rates.

Intricacy: Since VoIP/SIP is comparatively new, it requires staff experienced in telephony and IP data networking. However, service providers also offer managed services to mitigate deployment risk and ease design requirements.

Security Constraints

Threat: Connecting a device to the internet exposes the entire network to many types of threats. The VoIP Security Alliance or VOIP-SA has categorized possible attacks and threats on a VoIP system and made this information publicly available.

Importance of a stable platform: Firewall vendors have developed significant expertise in securing data communication. They design stable systems that are locked down to only admit services that have been configured to pass.

SIP Signaling: Firewalls with a SIP server and full SIP proxy play a critical role in maintaining enterprise security, and securing SIP trunks. SIP signaling includes messages in ASCII text, making it easier to read and control. Experts recommend encryption and authentication of SIP signaling.

Controlling media: Media can navigate the enterprise edge provided the SIP proxy opens the media ports allowing media to flow during the course of the call. Once the call is completed, media ports are closed. The SIP proxy approach is more secure than the IETF specified STUN/Turn/ICE methods.

SIP trunking implementation guidelines

Enterprise to use own SBCs: Even if the carrier has an SBC (Session Border Controller), enterprise should use own SBCs. These SBCs should be able to scale up.

Private LAN: While it is possible to place an enterprise SIP trunk on the internet, considering the obvious security issues, it is recommended to be best placed over a private WAN.

Usage of enterprise SIP trunks: It minimizes the demarcation sites to those that are strategic and redundant. The network must be typically designed to carry the enterprise SIP traffic.

Backing with UPS: With enterprise relying on few core network demarcation points, the edge components and primary network components should be redundant and backed up with UPSs.

Carrier diversity: If the enterprise has mission-critical requirements, carrier diversity should be considered.

PSTN Integration: When considering SIP trunking carriers, it is important to understand whether the carrier controls the SIP network all the way to the PSTN integration or not.

Call Admission Control (CAC) settings: When setting up the SBC, it is highly recommended to match the CAC settings to the session capacity provisioned.

Cost reduction through SIP trunking

SIP trunking helps reduce telephony expenses by up to 50 percent. The savings over traditional TDM trunking is achieved through the below mentioned steps and processes:

SIP trunking - negotiation best practices

Focus on ideal RFPs: By running proper RFPs enterprises can typically get rates of 15 percent to 20 percent lower than renewing rates.

Review rates annually: Sign fixed year contract and perform annual rate reviews for yearly rate decline benefits.

Pooling benefits: For better long distance rate discounts, it is advisable to purchase in advance a pool of minutes per month.

Seeking a single-rate long distance: It is ideal to have a single long distance rate for intrastate and interstate calling.

Tax estimation: Seek  an estimate of monthly tax and fee expenses from service providers.

Negotiate for a buffer: Negotiate for additional capacity to handle a surge in call volumes.

Bundling of services: Consider SIP trunk providers who bundle audio conferencing and other hosted telecom services.

Adopt fixed-rate billing: To keep a check on billing costs, it is advisable to buy SIP trunks. Some of the trunks also allow access to additional capacity.

Identify cost-effective routing: This allows to connect to multiple providers and route each call to the most cost-effective service provider.

Vendor selection criteria

A proper implementation of an effective SIP system can realise cost savings of as large as 50 percent; which is making the right selection of the service provider highly critical for large enterprises. The important vendor selection criteria are given below:

Quality: Running the voice and data traffic through the same network can reduce the cost drastically, however, the quality of voice and data services has to assured. An SIP trunking provider who owns and operates a network can ideally be considered for quality service.

Security assurance, interoperability of the service provider, experience and proven processes are other important criteria for choosing the right-fit vendor.


SIP trunking provides enterprises cost savings, streamlined operations and sophisticated multi-channel communication and opportunities. It helps large organizations to reduce the total cost of corporate communication, increase employee productivity and customer satisfaction. On the other hand, telcos can enjoy the benefit of using a single conduit for both data and voice, lowering capital and operational expenditures. While implementing SIP trunking system can provide several benefits, the enterprises, however, have to strictly follow the implementation guidelines. They have to make use of the negotiation levers and choose the right-fit service provider who can run both the voice and data traffic on a single infrastructure without compromising on quality and security.


COVID-19: Assess impact on your suppliers and ensure business continuity with Beroe’s WIRE
(World Instant Risk Exposure)