Tech mahindra
Tech mahindra

Time is running out for TDM

Posted by: TS Balaji On January 22, 2014 02:47 PM facebook linked in twitter

Having started my career with TDM technology and having worked deeply in “IP-fication” projects, it is not with uncommon interest that I have been following the TDM-to-IP row in the US.


FCC, the US regulator, had set a vision for TDM technology to be sunset and substituted by all-IP networks three / four years back. Recently the Chairman of FCC had blogged about the need to accelerate this (See also:, by Murali Madhavan for the challenges this transformation entails).

While, the ILECs (AT&T, Verizon, etc.) have been investing in fibre roll out and IP based offerings, which they believe would foster innovation and thus benefit customers, they have not been able to plan on turning-off their TDM infrastructure. This is because of another regulation in force that has enabled CLECs (CBeyond, Windstream etc.) to use ILECs' TDM infrastructure for access network, at regulated prices. In fact, this special access service and full number portability are perhaps the two important cornerstones that sustain CLEC business.

As per reports I have read, AT&T too had written to the regulator to accelerate this transition. They wanted to start conducting some limited experiments in 2014 towards a complete lights-off by 2020. There was also a proposal from AT&T to consider dropping of contracts with more than 5 year term for the regulated special access service that they extend to CLECs and move these to 3 year contracts or Ethernet access, both of which are more expensive.

The reaction from the CLECs was, understandably, very strong. They have also written to the regulator criticising AT&T's proposals.

Are ILECs Right?

TDM equipment, are designed and built to last - almost forever. However, in today's world, that would amount to over-engineering. Especially, since packet switched networks have flexibility to re-route packets around failed equipment, they entail lesser costs towards engineering up-time, compared to TDM.

The cost of TDM spares would go up as manufacturers discontinue them and start to look at future products which are mostly IP oriented. A grey-market for refurbished spares could spring up, causing reliability issues.

Unlike wireless operations, wire-line operations are more expensive. Operating networks of two technologies for wire-line services is quite unlike the co-existence of 2G/3G networks which is an incremental build on top of the previous generation. In fact, the closest in wireless world, for comparison, would be operating a CDMA network and a GSM network at the same time.

Lastly, the skills required to maintain and operate TDM infrastructure is becoming rarer by the day. There could come a day in the next 8 years when you don't have any more TDM resources to manage TDM infrastructure - at-least in the US.

So, in short, I feel that ILECs have a case.

Are the CLECs wrong then?

No. Their problems are the following three.

  • Fibre and Ethernet services are not as ubiquitous as copper is, yet
  • The dropping of long-term contract option will force them to charge their customers more than they do now
  • The cost of reaching single dwelling units / SOHO customers through fibre will be prohibitive, given their typical low-bandwidth communication needs.

Fair points, all.

Some questions

While eventually, the issue will have to be resolved only through a process that fosters consensus between ILECs & CLECs, here are some questions (look to views from readers on this) which arise in my mind.

  • If the whole argument is that of cost factors for ILECs operating TDM and IP infrastructure, won't the cost savings justify the movement; why should more expensive terms be proposed?
  • Given the success of OTT voice service providers & global ICT players (e.g. BTGS) who operate without owning an access network, why didn't the CLECs embrace such models in a big way? Why should they try to have an access business with all its dependencies on ILECs?

Some Observations

Irrespective of the outcome of the wrangle, I believe that the ILECs need to have a suitable Managed Services Partner strategy for the TDM network until it is switched-off so that they can focus on their strategic network. The rest of the World still continues to use TDM technology, which as per estimates must constitute 60% to 70% of existing networks, across the world. So, such a partner with Global Footprint may be able to bring the right skills needed to run the network.

CLECs who wish to migrate to an OTT model should also choose a Managed Services partner, who could provide a Converged IT and Managed Services approach to run their current setup, transform their IT systems and help migrate to their end goal.

Tags: Run Change Grow, Connected Industries
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