Mediation Remains Key to Next-Generation Networks

Channel Partners

May 1, 2000

10 Min Read
Mediation Remains Key to Next-Generation Networks

Posted: 05/2000

Mediation Remains
Key to Next-Generation Networks
By Charlotte Wolter

The platforms sometimes called “mediation switches” were pioneers in the movement toward call control using software and generic computing platforms that have culminated in what now is called a

This original softswitch was a highly flexible call control solution that usually was structured as software on a general-purpose computing platform.

Today, a second generation of softswitches, with a rich array of call features and other applications, is the star performer on the new-world telecommunications stage.

But that doesn’t mean that mediation switches or basic call control will fade into the sunset.

In fact, while service providers await the promised menu of features and applications, mediation platforms and softswitches are finding employment in several mediation applications that are useful immediately to service providers.

As long as legacy network equipment remains in general use–which looks to be at least another decade–service providers will need high-density, carrier-class switching platforms that can handle circuit-switched and IP traffic, and can mediate between the two worlds as needed.

These platforms, usually called mediation switches, replace and communicate with the Class 5 and Class 4 switches that give access to the circuit-switched PSTN.

“A mediation switch–or something–has to be there for the telephony over data to talk to the PSTN at the other end,” says Michael Howard, CEO, Infonetics Research Inc.
( “Something has to go between, and mediation switches do that. The SS7 switches have to do the actual call setup and teardown, but the request to do that moves from data network to the PSTN through one of these mediation switches.”

A mediation switch focuses on voice, a critical distinction from what is expected of softswitches as they mature. Any switch doing a mediation function must be able to switch time-division multiplexing (TDM) voice as well as IP voice, providing any-to-any mediation–IP to IP, IP to TDM, TDM to TDM, or TDM to IP.

A softswitch, by contrast could be expected to control the switching of ATM, frame relay, IP and TDM traffic, as well as provide a platform for the delivery of call features and service applications.

“I think of mediation as being the subset, the basic call setup” of
softswitches, says Jason Sayers, senior technologist, Williams Communications Inc.
(, which deploys Sonus Networks Inc.
( and Unisphere Solutions Inc.
( equipment for Internet offload and IP voice on its core network.

“To me, a softswitch goes beyond voice. Our goal today is to get a set of voice features running, but ultimately we could see this as applications that could offer more control over a packet infrastructure, such as streaming media control or any number of unified messaging services,” Sayers says.

What are now called mediation switches came from startups such as Castle Networks Inc., which is now part of
Unisphere; and TransMedia Com-munications Inc., which Cisco Systems Inc. ( acquired.

The early mediation switches were among the first platforms to deconstruct the traditional Class 5 architecture. They separated signaling and call control from the flow of the medium–usually voice.

Sonus, Uni-sphere, Convergent Net-works Inc. (, Lucent
Techno-logies Inc. ( and Ericsson Inc.
( are among those providing solutions that have mediation functions. Newcomers such as Tachion Networks Inc.
(, empowerTel Net-works Inc.
( and Santera Systems Inc.
( have announced products that have the requisite high-density “central-office-in-a-box” capabilities for mediation, and include much richer feature capabilities in the long run.

The Santera product even subsumes a multiservice access switch on its platform.

“These products overlap functions, and that is the problem” in defining a mediation platform or
softswitch, says Howard. "Sonus, Salix [Technologies Inc., acquired by Tellabs Inc.,, in December 1999], Tachion, etc. have chosen to carve out slightly different function sets, and they solve different problems. None of them do all the functions of a PSTN switch.”

That distinction is reserved for the Lucent
Softswitch, which has capabilities that come close to matching a Class 5 switch. But the price tag, reportedly $1 million,
limits its applications, says Howard.

In reality, there are no hard and fast lines between a softswitch and a mediation switch. In fact, many “mediation” platforms support many calling features.

“To me the lines blur,” says Vince
Rocca, chief technology officer and co-founder, 2nd Century Communi-cations Inc.

Rocca’s company uses the
Siemens/NewbridgeMainStreet Xpress 36170 switch and the PathMinder softswitch, from TeraBridge Technologies Inc.
(, a partner of Siemens Information and Communi-cations Network Division
( The MainStreetXpress and PathMinder provide 2nd Century with network intelligence, billing, call control and service management system capabilities to run voice over a packet network.

“A mediation switch is very nonintelligent,” Rocca says. “All it is doing is saying, ‘Here is the legacy network, and here is the next-generation network’ and we have to do the minimum amount of conversion activity to get between the two.

Charts: 1.Internet offload 2.Directory-Enabled Telephony 3.Converged
Backbone Service

“It is the same thing over and over, and has no feature intelligence. A full-blown softswitch gets into applications. At 2nd Century, we are doing a lot of mediation and very few applications, but we will migrate to more applications as time goes on,” Rocca adds.

Most softswitches that are currently deployed or are planned for deployment in the first half of 2000 will perform mostly “mediation” functions, such as offloading ISP traffic from Class 5 switches or converting TDM voice traffic to IP voice for long-distance transport on a private backbone.

Few calling features will exist, and no flashy applications will be involved, even though they are the hallmarks of softswitch functionality for the future.

“Because this is the first implementation of a softswitch, [vendors] are trying to do basic functionality,” Sayers says. “The next generation would add some special features, such as a service-creation environment for applications, or customers being able to do their own feature sets via a browser interface.”

The Classless Switch

It is characteristic of next-generation network switches to break down the traditional hierarchy of telephone infrastructures where CO switches are Class 5, and switches nearer the network core are Class 4 or tandem switches.

The next-generation switches are able to mediate calls between TDM and IP infrastructure at any point in the network, which is why mediation switches are sometimes called “classless” switches.

In the Williams application, “I would consider what we are doing more of a classless switch,” Sayers says. “Our biggest application is for Class 4 types of functions from a CLEC’s perspective. We would use it, as a carrier’s carrier, to enable a CLEC to provide local service in an area.”

Salix was one of the first next-generation switch startups and providers of a classless switch for VoIP or ATM. Tellabs is expected to incorporate Salix technology in its own softswitch that would include basic call-mediation capabilities, call features and applications.

Offloading the

Incumbent carriers complain about the load that dial-up Internet traffic puts on their Class 5 switches. For CLECs, ISPs and other next-generation carriers, the problem is more acute. They often do not own Class 5 switches and must pay the ILECs premium rates for their CO switch usage.

A priority among these carriers has been a solution to switch that traffic directly to their aggregation platforms before it reaches the CO switch.

“A lot of them are using these [mediation] switches for tandem offload to increase their tandem capacity without replacing switches,” Sayers says. “The idea is, if a phone call is an Internet call, let’s not put it through the voice fabric, and the voice switch will not get loaded with nonvoice traffic. That is also a pretty good application for media gateways.”

In Internet offload, the mediation switch recognizes a call as a dial-up Internet call on the basis of the number dialed and routes it directly to an ISP without going through a Class 5 voice switch.

In December, Convergent Networks Inc.
( announced a two-year, $50 million deal for 75 of its Integrated Convergence Switches (ICS2000) with Global NAPs Inc.
( for Internet offload. Global NAPs is a regional carrier on the East Coast that provides voice and data services to high-volume business customers, such as
WebTV, Mindspring, Netcom and Ziplink.

The Convergent platform includes call control embedded in the switch itself, rather than only on the feature server. The com-pany says this allows the platform to scale more easily than others because it is possible to combine the call capacity of several switches to make a single virtual switch.

Convergent also is one of the few platforms based on an ATM switching fabric.

Sometimes gateways associated with a mediation switch or softswitch handle the task of Internet offloading. In fact, basic switching and Internet offload are “more a function of the gateway part of the
[softswitch] product,” says Tom Valovic, analyst, International Data Corp. (

Adds Sayers, “Most of the media gateway vendors have this as one of the applications that they target when talking to CLECs.”

In February, Sonus Networks unveiled its System 9200, a combination of its earlier mediation platform with its SS7 signaling gateway and some softswitch functions to make a turnkey solution for offloading Internet traffic from Class 5 switches.

In the future, it also will have the ability to offer softswitch-type functionality with call features and applications.

A Current Analysis report says the System 9200 does not offer the density of some competing products. It also states that the product puts Sonus in the running in the Internet offloading category, where it previously did not have a product.

Convergent partnered with Marconi Communications, the U.S. subsidiary of Marconi plc
(, in January to create a product that combines Convergent’s Integrated Convergence Switch with ATM technology from
Marconi, aimed specifically at the Internet offload application.

The Convergent ICS2000 interfaces with a carrier’s end office switch via a trunk line and delivers low-cost connectivity to the service provider’s remote-access servers.

IP Voice

2nd Century Communications uses the Siemens/Newbridge/TeraBridge combination in a network configuration that puts most intelligence and features at the customer premises while using the backbone network for large-scale voice and data switching.

“In our model, we are using a mediation device, or a scaled-down softswitch, to mediate between the legacy network, the PSTN and the Internet and next-generation packet-based networks,” says Rocca. “The difference between our implementation of the softswitch or mediation device and others is that we believe the softswitch should perform just enough functions and features, or be just intelligent enough to allow it to connect to legacy networks. Complex functions should be pushed to the edge, to the customer premises.”

2nd Century’s rationale for its configuration is that the last mile is the most expensive bandwidth for a competitive carrier, because it usually is leased from an ILEC. By contrast, bandwidth at the customer’s premises essentially is free.

“By pushing intelligent features out to the edge … you can lower the overall
cost to deliver service to the customer,” Rocca explains.

“We use DS-1s today and will use DSL in the future to gain access to customers,” he adds. “We will replace equipment for key systems, firewalls, e-mail servers and VPN services, all at the customer premises. The switch just acts as mediation device to PSTN and to the Internet.”

As a result, 2nd Century’s up-front cost per PoP is in the range of $500,000 per city, compared to $5 million to $7 million if the company deployed Class 5 infrastructure, Rocca says.

“So we have one-tenth the capital cost up front, per city, and we put one switch in each city.”

Charlotte Wolter is infrastructure editor for PHONE+ magazine.

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