TDMoIP and voice-over-packet solutions are part of a new and exciting trend in the telecom market. RAD is the pioneer and leader in these areas. In this presentation, we will discuss the need for TDMoIP and voice-over-packet solutions, the ways in which they are implemented, and RAD’s product offerings.

First, let’s take a look at typical access strategies used by carriers and service providers worldwide.

On the right side of this diagram, we see the customer premises. This includes legacy equipment used for traditional services and next-generation equipment for new services. On the left, we see different networking options.

This structure demands different network cores for different services, as well as different Customer Premises Equipment for each service.

The arrows illustrate how legacy services are mapped into legacy transmission networks, while new services are mapped separately into new packet switched networks.

Frequently, traditional carriers operating traditional networks want to begin providing new services. New technologies for this scenario are launched every few years. For example, RAD is a leader in equipment that maps Ethernet and IP services into ATM while enabling use of new protocols implemented for next-generation SDH and SONET, such as GFP. RAD offers products that use protocols for mapping IP traffic into virtual containers in SDH and SONET networks.

This brings us to the core need for voice over packet solutions: carriers want to replace legacy networks with packet switched networks, while retaining the integrity and quality of legacy services.

Service providers that have deployed next generation equipment are limited to offering Ethernet-based services – mainly data and VoIP. This is due to the fact that packet switched networks are specifically designed to transport IP and Ethernet traffic. Providers that want to expand their customer bases to include those who also want legacy services, they must find a cost-effective way to include high-quality TDM to their offerings.

Traditional carriers tend to do most of their business in traditional services, with the most lucrative being TDM leased lines. Packet switched networks cannot deliver leased lines – hence the need for TDMoIP and voice-over-packet solutions.

The basis of voice-over-packet solutions is the creation of emulated circuits through the packet switched network. These are known as pseudowires.

To create pseudowires over packet switched networks, which then take the place of legacy networks, it is necessary to tunnel transparently across them. This is commonly applicable for native services such as TDM, Frame Relay, ATM and Ethernet. Pseudowires must have minimal effect on the original characteristics of the services they carry

Numerous standards bodies are working together with major industry players to define protocols for pseudowires. These include the IETF, the ITU, the MPLS/FR/ATM Alliance, and the Metro Ethernet Forum.

Three main applications are being standardized. The first is unstructured, or structure agnostic. The second includes structured and structure-aware applications – these enable applications such as end-to-end framing and loopbacks. The third is voice trunking, which enables effective transmission of multiple voice channels over the packet switched network. Some of these standards have been released – for updated information, see the standards bodies’ websites.

RAD is a leader in the development and implementation of pseudowire gateways. The company offers two product lines in this area – the Vmux line and the IPmux line.

Let’s have a look at the Vmux line. Solutions based on these gateways enable carriers, operators, call centers, and enterprises to provide voice trunking over TDM and IP networks, with a voice compression ratio of up to 16:1.

RAD’s other pseudowire product line, the IPmux line, is aimed at the carrier, operator and enterprise markets characterized by the need to connect legacy voice switches and PBXs. These gateways enable leased line emulation over packet switched networks, including clear channel applications. Clear channel applications provide TDM connectivity over the packet network with minimal delay, full transparency and end-to-end synchronization.

We’ll now take a closer look at the IPmux product line. Our focus will be its capabilities and its place in the network.

As we all know, it is far more cost-effective to transmit data over packet networks than over traditional networks. In recent years many alternative, competitive carriers have built packet switched networks around the world. Much of the capacity in this infrastructure remains unexploited. Network owners find that utilizing this unused infrastructure to provide lucrative services – such as leased lines – is a very attractive business proposition.

Carriers must also protect the end user’s investment in legacy equipment, which is often reliable and in good working order. End users are not motivated to replace these devices – this is a costly process in terms of equipment and truck roll outlay. Besides, why move to a new technology if the current one works well? As such, carriers want to offer customers what they need without convincing them to change equipment.

With its full transparency and minimal delay, the IPmux answers the needs of both the carrier – in terms of cost-effective implementation – and the end customer – in terms of adding services over legacy equipment. The gateway’s end-to-end synchronization is crucial – TDM networks must use a clock, and customer-located equipment cannot work without it.

This slide shows us how various IPmux gateway models work within a generic application.

On the right side of the diagram, we see customer sites in which various IPmux TDMoIP gateways are installed. These provide the services and interfaces needed in typical customer sites. From the top, we find analog interfaces (ISDN, LAN), then TDM interfaces (E1, T1, E3, T3) and finally Ethernet interfaces. These examples show how the IPmux line provides TDMoIP gateways for the full range of CPE and service needs. Each IPmux model features a different capacity level and interfaces, in order to optimize the CPE according to each site’s needs. Without such tailoring, it is easy to order equipment of a scale too large for specific sites. This is expensive and can even lead to non-deployment.

As we follow the data stream to the left of the gateways, we see all of the traffic moving into a packet network. This network can be based on any technology that carries Ethernet and IP traffic – whether ATM, SDH or SONET.

Exiting the packet network to the left, we find our datastreams entering 2 typical RAD central office, or POP devices – the IPmux-16 and the Gmux-2000. The IPmux-16 handles the fast Ethernet traffic, distributing it into E1/T1, E3/T3 or CT3/STS-1 streams.

We’ll take a look at the other gateway, the Gmux-2000, in the next slide.

The Gmux-2000 operates on a different scale than that of the IPmux line. It is designed to interwork between the packet network and the traditional SDH or SONET network. It can groom multiple TDMoIP streams from the packet network and pass them to the SDH/SONET network via E1/T1, E3/T3 or STM-1/OC-3 streams. As necessitated by its position in the network, the Gmux-2000 features a high level of redundancy. It supports protected SDH/SONET interfaces, packet network interfaces and redundant infrastructure such as power supply. Co-located with large transmission equipment, the Gmux-2000 features a very small footprint.

Let’s move on now to the Vmux product line.

There’s a lot of buzz about using VoIP technology to transport telephony services over packet switched networks. The Vmux product line uses a different approach.

Before delving into the Vmux, let’s have a look at voice trunking. Voice trunking is inherently different from voice/data integration. It involves transmission of the bulk of your voice traffic over a packet network, from one edge of the network to the other. Here, bandwidth efficiency is crucial. Voice trunking is therefore very different from VoIP, where you use IP telephony technology to transmit corporate and carrier voice services.

The chart on this slide compares the efficiency of voice trunking with RAD’s Vmux to that of VoIP. The two Vmux units in this comparison use the G.723.1 coder at 6.4kbps, with 50% silence suppression. The higher the number of channels transported from one edge to the other, the more efficient the Vmux becomes compared to VoIP. For example, when transporting 60 channels on 2 E1 lines over a packet network, the Vmux consumes 60% less bandwidth than VoIP. The Vmux is optimized for this application, so it complements VoIP as opposed to competing with it.

Now that we’ve covered the background, let’s see how some Vmux applications work in the field.

This slide shows how the Vmux works in a common corporate scenario. It can be a local, remote, or even international application. It enables you to connect a set of PBXs to each other over the IP network, or even over the public Internet.

On the right side of the diagram, we see remote sites. Each of these is equipped with a Vmux gateway that connects the local PBXs and LANs to the packet network, via a variety of last-mile technologies. The Vmux ensures high quality voice services while saving bandwidth in the IP network.

The Vmux provides compression up to a ratio of 16:1, subject to the silence level. The level of silence suppression used varies throughout the world, as different language and cultural groups tend to use different silence levels according to their needs.

This slide shows how the Vmux works in a common cellular scenario. Field deployments in this type of application have proven very successful. When using the Vmux to connect mobile switching centers over TDM or IP networks, there is no significant degradation of voice quality.

Transport costs are a major bottleneck for cellular operators – an estimated 60% of their budgets goes to backhaul and transport operations. Our installed base shows that the Vmux helps operators reduce these costs without sacrificing voice quality.

We’ll now focus on a point-to-multipoint application. In this scenario, the voice trunks are transmitted between the headquarters and remote sites over a TDM network. TDM networks are still in use in many parts of the world, and many of them are not likely to be replaced by packet networks in the near future. The Vmux allows transmission of Ethernet and traditional voice services over the TDM network, plus the ability to offer fractional E1/T1 services. At the remote sites in our diagram, it acts as an IP router, mapping the IP frames to transmit the fractional E1/T1 trunk over the TDM network.

Note that in this application, the Vmux provides only a transmission solution. This is very different from VoIP, which implements a new set of protocols and signal characteristics. This hampers some features native to the traffic. In contrast, the Vmux transparently supports signal protocols and other characteristics of the datastream.

Let’s move on now to international voice transmission applications. Many international voice carriers have implemented the Vmux in a variety of applications. By doing so, they take advantage of the Vmux’s ability to interface with any transmission technology capable of carrying IP and Ethernet traffic.

This diagram shows how the Vmux fits into international voice networks based on satellite links, TDM lines or IP networks. Note how the same Vmux unit can link with any transmission medium offered as a trunk by an international exchange carrier. For example, you can make the link via an E1/T1 leased line and switch later to a satellite connection that has since become more economical. The Vmux applies the same level of service over any media – for example, it compensates for echo caused by end-to-end delay.

Our final example shows the Vmux in a call center application.

As we all know, international call centers are used extensively. North American customers often talk to call centers in South America or India, Europeans often get phone support from North Africa, and so on. This application simply requires effective transmission of voice traffic over international infrastructure.

The Vmux fits perfectly here, as it can provide connectivity over the satellite, IP, or TDM leased lines used as the international link. This is a very attractive application for the Vmux, and RAD has seen much success with it.

We’ve now completed our look at the world of TDMoIP. We started with the mapping of TDM-through-wire access applications. We then took a look at pseudowires, where we focused on the most common applications in this emerging arena – TDM pseudowire. We moved on to the 2 product lines RAD offers in this area – the IPmux family for leased line services over packet networks, and the Vmux family for voice trunking over both legacy and next generation packet switched networks. Finally, we saw a variety of compelling customer needs to use these products.

For further information, you are welcome to consult with your local RAD representative.