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May 1999

What It Takes To Join The Carrier Class


With the emergence of a new IP/ATM WAN network architecture comes a new breed of carrier products, referred to as "media-aware" switches. These products are designed to support a whole host of circuit and packet-based services for converging the WAN access and core. They have been specifically designed to address the stringent requirements needed to maximize service revenues and network uptime, and they must meet the same standards as today's circuit-based products. However, the concept of carrier products goes beyond the words "carrier-grade" and Telcordia Technologies' (formerly Bellcore) Network Equipment Building Standard (NEBS).

It becomes increasingly strange that the terms "carrier-grade" and "carrier-class" are so loosely used in the industry. What's even more amazing is how these terms are defined by many, especially the product and service categories they fall into. The area largely affected is classifying which products fit into the telephony segment.

Over the past year, we've seen a big paradigm shift in the telecommunications market regarding how the next-generation network will be designed and implemented. The market for the new telco arena is projected to be large - read any recent market report to get a feel for the billions of dollars that will be attributed to these new networks. Because of this, vendors are targeting new and existing products to ensure, from a positioning sense, that they can somehow differentiate themselves from the competition. However, most believe that because their product has been certified NEBS-compliant (Telcordia specification for what we call "shake-n-bake" test), that they are carrier-class.

All this means is that the product passed a stringent test for mostly environmental conditions - kind of like getting the USDA stamp of approval! This is an important item, especially for an ILEC, CLEC, or any carrier that requires collocation in central offices or point-of-presence locations that require this certification, but should not be the only item that would warrant this grand title.

Another area includes products that support DC voltage, or even some that are CompactPCI-compliant with the tag line of "carrier-grade" - all attributed to hot-swappable modules, or redundant power supplies.

Enough already! We rarely see a compilation of the other functionality and performance requirements which need to be met to support this "holy grail" carrier-grade term - a term that is increasingly being redefined as carrier-quality.

In addition to the environmental requirements, the other areas service providers should take into consideration include:

  • Performance: Low-latency, de-jitter, minimal delays attributed to packet processing.
  • Quality: Toll quality, manufacturer quality (ISO 9001, ISO 9002).
  • Signaling: SS7, Q.931, CAS, MF.
  • Resiliency: High-availability and high-reliability, 99.999% available uptime.
  • Scalability: In terms of thousands of ports within a rack space.
  • Management: OSS, including billing (CDRs).
  • Migration: Circuit to packet, circuit signaling, and packet interworking. Interworking with existing voice switches, and circuit-switched services and features.

Service providers will not tolerate downtime in the network. Any single point of failure is catastrophic to the revenue generating aspects of their business. Telephony is the "bread and butter" of all ILECs and IXCs in the market today - you can always pick up a phone and make a call (unless of course there's a natural disaster), and equipment in the network should not cause the circuits to become unavailable for use. The current telephony infrastructure has been designed to help avoid such outages, both from the equipment side and the network route end.

Today's network service providers and equipment vendors have put in place mechanisms to notify end users of unavailable service. For example, on Mother's Day, if the end user can not place the call through the network due to congestion, they'll be notified with a "fast busy" or an announcement of "All Circuits Are Busy." These conditions were put in place to ease end users' minds so that they still have connectivity to their carrier or service provider. Granted, they don't like to hear this, but it does reassure us in some strange sense that there is something moving through the other end of the wire and the phone jack.

The other side of having high availability and fault-tolerant capabilities is the carrier and service provider resources. The requirements for providing fault-tolerant hardware and software are meant to lessen the need for rapid response to failures. Not all sites are fully staffed, and require a good MTTR (Mean Time To Repair) cycle in order to make physical changes to the equipment.

For telephony circuits, there are mechanisms in place to help identify and troubleshoot lines and paths of the network. Proper detection of any fault within the network and resolution must be capable of moving into the new generation voice-over-packet model. This includes fault isolation on call setup, such as Continuity Test (COT), tone detection and failure, and test line (including loopbacks). This is on the circuit and signaling side of the path, and there is also the behavior and testing of the packet side of the network, including packet performance, statistics, and test inject functions. The goal is to isolate and remedy the problem as quickly as possible.

Signaling aspects also need to be looked at when evaluating your particular requirements. Signaling System 7 (SS7) is the most common signaling access interconnect between switches and networks today. It also provides the mechanisms to leverage the existing Signal Transfer Points and Signal Control Points for Advanced Intelligent Network/ Intelligent Network feature sets, including the requirements for supporting LNP (Local Number Portability). LNP is key as it will become a mandatory function for any carrier or service provider. LNP support allows end users to maintain the same telephone numbers if they switch their local carrier or service provider. There are also the interconnects between switches that range in the Feature Group D spectrum (bearer channels and signaling) - Q.931, SS7, etc., and IMT (Inter-Machine Trunks).

Signaling is one of the most important items when evaluating the requirements for integrating both circuit and packet-switched technologies. There are new frameworks and requirements that are being worked on within the IETF, ITU-T, ETSI, and Telcordia standards bodies to help define these interworking issues.

When we talk about carrier-quality, one of the items that comes to mind is voice quality. There's been a long-standing notion that migrating circuit to packet won't give users the same voice quality as they are receiving today. Most of this controversy is based on early implementations of voice codecs and digital signal processors (DSPs). The emerging media switches are leveraging newer DSPs and are improving the packetization schemes to deliver toll-quality voice. Earlier implementations of packetized voice attributed more than 150 ms of delay for an end-to-end voice call - this doesn't include any network delays, which can be more than 100 ms and even greater when these technologies are used across the public Internet or across international circuits. Since the public Internet is not deterministic, you can never achieve toll-quality voice through it.

Carriers and service providers are starting to deploy private packet networks that are optimized for carrying multimedia traffic, and in particular, voice. New media switches are also being optimized to ensure less than 50-ms, end-to-end delay for voice packetization and depacketization processes, including the use of dynamic de-jitter buffers, programmable packetization intervals (the sampling of voice packets), and echo cancellation technologies based on both G.165, and G.168 for tail-end echo.

Integrating with existing OSS platforms is also key for provisioning, billing, and management (service, operations, engineering, costs, etc.) aspects. OSS operations are important for the overall provisioning and maintenance of the end-user service - they're also the vehicle for revenue collection. However, vendors will want to ensure that new applications can be easily added to the carrier and service provider product portfolio, through standard-based APIs.

Scalability is paramount, especially for carriers and service providers who want to open new cities to services. The ability to start with a very economical entry point - 200 voice ports is a fair number - to supporting multiple thousands without a fork-lift upgrade and new frame, or major equipment installs, is extremely important. The interface scalability should reach from DS0s to higher-order interfaces including DS3s/E3s and SONET/SDH interfaces on the access/trunking side, as well as high-performance packet/broadband interfaces.

The other defining moment with new carrier-grade media switches is the collapse of multiple services/functions within a single platform. The ability to introduce new services without deploying additional equipment will give carriers and service providers competitive advantages when developing new services for their customers.

It's a brave new world out there - the services that will, and can be offered, are endless. They require that service providers look at solutions that will offer the best migration strategy, while providing them with an open platform architecture for future network and service requirements.

Randy Brumfield is director, product marketing for TransMedia Communications, Inc. TransMedia is delivering a new-generation "media-aware" switch that gives carriers a new edge - bridging the gap between high-performance Internet/packet (IP/ATM) network and traditional public network communications (PSTN).

Why H.323 Compliance Is Not Enough For Carrier Products


Internet telephony growth is currently constrained by lack of interoperability between telephony platforms. Anyone who has attended a voice-over-IP (VoIP) function within the last six months has surely seen interoperability listed as one of the major problems facing the industry. As such, carriers that are planning, building, or operating VoIP networks need an interoperability strategy to maximize the value of their networks. Internet telephony platforms from different vendors do not interoperate, despite each vendor's claims of being "H.323-compliant."

Although Version 2 of the H.323 protocol is currently published, some of today's products are based on Version 1, while Version 3 is expected to debut this year. Because there are various incarnations of H.323 and many allowable choices within each one, it is a virtual certainty that no two H.323-compliant products will work together "out of the box." In the past, in order to achieve interoperability, H.323-compliant vendors had to reverse engineer each other's products or collaborate for months to get their products to interoperate.

To eliminate the need to perform "one-off" projects in order to achieve interoperability, the iNOW! (Interoperability NOW!) initiative was launched. iNOW! is a broad-based, multivendor effort established to provide interoperability among Internet telephony platforms. The iNOW! Profile (www.inowprofile.com) is a public document that defines the exact options manufacturers can use within H.323 and other relevant standards to quickly achieve voice and fax interoperability.

There are three types of solutions to the issue of Internet telephony component interoperability:

Gateway-to-Gateway Interoperability: This type of interoperability enables different brands of gateways to exchange calls. Networks with gateway-to-gateway interoperability place extra administrative demands on the carrier. For example, the carrier must operate a matching gatekeeper for each brand of these gateways.

Gateway-to-Gateway Interoperability + Gatekeeper-to-Gatekeeper Interoperability: Type 2 interoperability provides the same functionality as Type 1, but is much easier to administer. As with Type 1, the carrier must operate a matching gatekeeper for each brand of gateway; however, each gatekeeper only needs to know about its own brand of gateways since all gatekeepers now have a relationship with each other.

Gatekeeper-to-Gateway Interoperability: Type 3 interoperability enables gatekeepers of one brand to directly communicate and control gateways of another brand. Type 3 functionality can enable a network of different brands of gateways to work under the control of a different brand of gatekeeper.

Types 2 and 3 working together represent the "Holy Grail" of Internet telephony interoperability because they allow the carrier to run a mixed system of gateways with only one brand of gatekeeper. This combination provides one large system that has true plug-and-play capability, enabling the carrier to mix and match gateways without being forced to administer multiple gatekeepers. This type of network can seamlessly share traffic with other similar networks around the world.

When Internet telephony equipment has "plug and play" interoperability, carriers can buy equipment from any vendor(s) they want without worrying that the equipment will not operate in their network. This creates more competition, lowers equipment prices, and levels the playing field. Interoperable networks are also easier to administer. Interoperability allows carriers to share traffic with exchange carriers, peers, and bilateral partners, which lowers the carrier's cost to complete calls. This also creates a new source of revenue for calls coming into the carrier's service area.

Interoperability will set the stage for lower equipment prices as well as a more competitive service environment for carriers. Lack of interoperability hurts carriers that peer with other networks or use exchange carrier services. In a world without interoperability, the carrier must choose to standardize on one proprietary vendor; operate multiple parallel networks of incompatible gateways from different vendors; or wait for interoperable equipment to appear.

Carriers issuing Internet telephony requests for proposals should require bidders to explain their interoperability strategies in detail. As we've learned, buying equipment that is H.323-compliant is not a strategy. Select an equipment vendor that has a proven commitment to interoperability and is an active player in industry interoperability initiatives.

Ed Hirschman is senior product line manager for Internet Telephony Exchange Carrier ITXC Corp. ITXC's WWeXchange Service offers intelligent routing, authentication, authorization, and settlement to its affiliates. ITXC is a wholesale provider of services to companies originating and terminating Internet telephony calls, and is the first carrier to exchange calls in a commercial environment between gateways manufactured by different vendors.

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