Latest Significant Trends in SIP Trunking

Latest Significant Trends in SIP Trunking

By Stephen Leaden July 26, 2016 6 Comments
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Latest Significant Trends in SIP Trunking by Stephen Leaden


SIP trunking is no longer for those who are pioneers in IT or forward thinkers. SIP trunking is now a "have to" technology that requires significant best practices to secure a safe, risk managed implementation and support.

SIP trunking has been promoted as a carrier solution for close to 48 months at this juncture, and has now, for all intents and purposes, gone mainstream. SIP trunking offers several key benefits for those enterprises willing to take the plunge and implement it.

SIP Trunking Benefits

There are several key "out-of-the-box" benefits one can leverage:

  1. Annual Cost Savings – Annual cost savings are significant, in our experience between 20% and 60% annually. In fact, SIP trunking savings in our experience has increased by at least another 10-20% in the last 24 months. These savings can make any IT Director or CIO a hero. For our clients we have seen savings annually from $200K to $1.5M annually and more. Now is a great time to consider moving to SIP trunking, just based on cost savings alone.
  2. SIP Trunking Reduces Managing the Number of PRIs Across Multiple Sites – For many customers, the number of PRIs to manage can be from several to many.  SIP trunking dramatically reduces the number of PRIs necessary to maintain public inbound and outbound traffic. We have one client with in excess of 100 PRIs in use across multiple sites. For this client, the plan is to reduce the number of PRIs by 90+% (some to be kept for overflow purposes). This is a major benefit for managing the network on a day-to-day basis.
  3. Most SIP Trunking Providers Deliver on Real-Time Statistics – Most SIP trunking providers deliver on real-time statistics for use by the enterprisefor capacities and therefore gives you, the enterprise user, a real-time view of what traffic utilization is taking place on your SIP trunks, giving you visibility on use and session/port utilization.

Some Interesting "Points/Tidbits" About SIP Trunking

SIP trunking facts and characteristics are interesting, and you should be aware of the following:

  • Most PRIs Today Are IP Already – What you may not be aware of is that most PRIs implemented today are actually on gateways and native SIP "behind the scenes," being converted to PRIs before they interface with your PBX, VoIP, or Unified Communications system.
  • PRIs Are No Longer Being Sold In Some Parts of the Domestic U.S. – In some parts of the U.S., major carriers have already announced that PRIs will no longer be sold, period. SIP trunking is now the defacto voice service being sold in those areas.
  • SIP Trunking Is Disruptive to the Market, As were PRIs 10 Years Ago – SIP trunking is a newer technology and it has been our experience that the same "learning curve" by the carriers experienced with PRIs 10+ years ago is now taking place once again with SIP trunking. SIP trunks take up to a day to turn up and test, similar to PRIs when they first showed up. Today SIP trunks should be turned up leveraging a detailed test plan in order to ensure that SIP trunking uptime, failover, call flow, stress testing, network QoS, number portability and key number forwarding are all available. In addition, intelligent network management tools should be utilized to proactively manage a possible SIP trunk outage at some juncture.
  • SIP Trunking is Complex and Can be Risky if not Designed Right – Best designs for SIP trunking should be redundant and diverse, with failover across multiple trunks. SIP Trunking requires SBCs (see below). SIP Trunking requires PRIs as a part of the back-up process. SIP Trunking must be implemented with a thorough test plan for QoS, redundancy, failover, bursting, stress, availability, jitter, loss, latency, physical security, extended demarcs, and reporting on such.   
  • SIP Trunking Network Assessments are now Available – Some vendors now offer SIP Trunking Network Assessments, to ensure SIP Trunking, QoS, and other characteristics are ready for prime time and a full production environment.
  • Customer/Enterprise-Side SBCs are Required – Our team has long been a proponent of enterprise-side Session Border Controllers (E-SBCs) as required for any enterprise customer. They provide four distinct benefits:
    • Security – To protect your environment against data-driven attacks, such as DOS and DDOS and many more (don’t assume the carrier delivers on all best practices with carrier-side SBCs only). SIP trunking is a data service and therefore security rules apply
    • Normalizes SIP Traffic – Most carrier and UC systems interfaces are not pure IP and therefore need a technology tool to normalize SIP traffic
    • Provides Session Management – To facilitate dialing and integration between legacy and currently supported UC systems
    • Collects Data for all Call Types – Including voice calls (inbound, outbound), mobility calls, conference calls, federated calls, and future applications for IM/chat and video over SIP trunking for possible bill back.
  • Vendor SIP Trunking Contracts can be Different – Vendor contract components and performing to those contracts can be a real eye-opener. For example:
    • There are numerous components we came across – the top three in my opinion include (1) no call recording allowed (therefore eliminating Contact Center traffic), (2) no 911 accountability, and (3) penalizing the customer for short duration calls with "additional fees." (There are several others, too many to list here – if you would like to know, please more drop me an email @ These sound almost ludicrous, but these terms are out there among some of the SIP carriers. Be sure to thoroughly vet the fine print on SIP contracts – it can be eye opening.
    • Another vendor’s contract missed on delivering one-time and recurring credits promised to the client in the proposal, based on the original RFP and evaluation. The "miss" and possible increases added up to in excess of $500K between what was bid and what actually was going to contract.
  • Enterprises Need to Account for Public Side SIP Traffic – Anywhere between 20% and up to 70% of voice traffic is external, and such volumes need to be added to the design of the current WAN where public side SIP traffic will now traverse the private WAN as well. Without accounting for such, SIP trunking volumes can possibly "choke" a WAN’s bandwidth during peak peak traffic volume periods.

Current Trends in SIP Trunking

SIP trunking has come a long way, and some of the latest trends you need to be aware of include the following:

  1. Enterprises are Looking at SIP Trunking Disaster Scenarios – Some of the carriers now offer some level of disaster recovery, whether it be failover, reroute, or bursting. Depending on your own needs, these areas are key for "betting" on a SIP trunking solution.
  2. Carriers Have Improved on SIP Sessions Costs – The latest offerings on SIP trunking include more aggressive costs for sessions for possible over-design, failover, and adding sessions "on-the-fly" as needed.
  3. Most of the SIP Providers Offer a Higher Availability Model – Many of the SIP trunking providers offer a 99.99% higher availability model vs. the more traditional 99.9% model. This manages down the defacto outage of 8 hours annually in the vendor network and reduces it contractually to a 1-hour outage annually, a significant drop. This in reality, however, in my experience is more about contract language than the reality of circuit reliability of 99.99%, and therefore redundancy and diversity are still critical components in the design of SIP trunking.
  4. SIP Providers Offer Better Usage Rates – The trend for usage rates continues downward. In some cases, SIP trunking minutes can effectively be designed for an equivalent flat rate, similar to mobility plans on a larger scale. Enterprises need to plan in the design not just for day one, but to also consider possible growth and seasonal variations for up to 36 months out (if a 36-month agreement).
  5. Diversify With PRIs (Either from the Same Carrier or Different Carrier) – At first it seems logical to use a second set of SIP trunks for diversity purposes, however, during this industry transition period with migration to SIP, PRIs are tried and true and in some cases running on a separate network and therefore network diversity. 
  6. Consider Third Party SIP Trunking Carrier for Diversity – In addition to PRIs at key locations, a second SIP trunking provider can be leveraged for network diversity purposes, in the event one carrier’s network is totally out of service for an extended period (we've seen it).
  7. Other Forms of UC Will be Coming and Offered as a Part of the SIP Trunking Suite – Other forms of UC will be available in the near future for use over SIP trunking. These include conferencing, mobility/twinning, and now video and chat as real-time components that require QoS. Expect carriers to begin offering these additional services in the next 12-18 months.

Summary and Conclusions

SIP trunking has come a long way and has gone mainstream. We help our clients leverage a best practices approach to SIP trunking by designing for redundancy, diversity, bandwidth for growth, and future considerations for conferencing, chat, video, mobility and other media, going through a thorough vetting process, and implementing to best practices to ensure a high quality SIP trunking experience.

Changes in the market in the last 24 months have been significant, and yes, the market has matured. The advantages and benefits to SIP trunking are significant, and it is time to take advantage of a going-forward technology that replaces PRIs and other legacy services long term.

SIP trunking can also be your entrée to leveraging newer UC technologies, and the savings can create just the leverage you need. We’ve done it for our own clients.


6 Responses to "Latest Significant Trends in SIP Trunking" - Add Yours

Roberta J. Fox 7/27/2016 8:13:34 AM

Stephen - Great overview on SIP trunking! You also have provided readers with the how-tos, and gotchas! We see our Canadian clients lagging by about 2 years from yours, primarily due to legacy carrier influence. As long as professionals such as you and I educate and inform clients about SIP technologies, we will help them advance the deployments and gain the real technical and financial benefits.
Ajit Kumar 7/28/2016 7:24:39 AM

thanks Stephen for writing this! very informative.
Tahir Yasin 7/28/2016 2:38:21 PM

Thank you for great update , what about session based pricing , Any outlook on flat rate session based pricing ?

Steve Leaden 7/29/2016 5:27:31 AM

Thank you Roberta!

Agreed - we design and help implement SIP trunking regularly as a key component of our practice. We really enjoy educating our clients and are a resource to help and gain the many benefits associated with SIP trunking! It is complex as the article shares, but the benefits far outweigh the complexities and a must MUST going forward.

Thank you again Roberta! Steve
Steve Leaden 7/29/2016 5:29:06 AM

Ajit - thank you for you comments!

Please feel free to reach out if you have any questions! I can be reached at
Steve Leaden 7/29/2016 5:56:22 AM

Tahir -

Thank you for your comments, appreciated.

Regarding session-based pricing, yes the carriers have been charging for sessions for some time as a component of the overall SIP trunking model. The model also can include the SIP circuit, QoS, managed hardware, redundancy, bursting, extended demarcs, failover, redirect, DID charges, and more. The cost per session, depending on the carrier, can be offered to include 'xx' minutes. Note that additional minutes are subject to usage costs.

I expect this trend to continue towards a more flat rated model over the coming 24-36 months. Vendors are also beginning to include some level of bursting (as we have seen with Internet circuits), but requires additional planning as session bursting is not quite immediate.

Thank you again and if any questions, please feel free to reach out to me on email


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