MCI's Releases Private IP VPN To Improve VoIP

Claim: An expanded network-based VPN offering will let MCI give preferential treatment to more applications. A jitter SLA will help ensure that IT gets the VoIP it pays for.

Context: The market for VoIP services is hot, with all the top carriers delivering some offering. This is particularly true for VPN services supporting VoIP.

Credibility: MCI was an early leader in both hosted VoIP services and the VPN space. This should add up to strong market leadership, but competitors are delivering tougher SLAs than what the company's Private IP service currently offers.

As enterprises converge around a common voice and data network, many will need more than just the usual three classes of service for their corporate WAN. This month, MCI will answer that need by adding four more service classes to its Private IP VPN service.The move demonstrates the increasing maturity of converged network services. Service providers are augmenting their VoIP offerings to tackle the unique requirements of large enterprises, whether by adding performance levels, filling niche requirements, reaching overseas, or addressing how best to handle remote offices.

Although MCI held the early lead in converged voice and data services with its Advantage hosted voice offering, it's feeling the pressure from market rivals. Last fall, we saw the expansion of services by Sprint and Global Crossing. Then, in December, AT&T released VoIP as part of its VPN portfolio called Voice over VPN. Those services offer features and SLAs not available from MCI. Expanding the number of service classes will help the company, but it's still going to be hard-pressed by the competiton.

SERVICES GALORE

For network architects, perhaps the biggest challenge will be figuring out not so much the slight technology differences between comparable services, but what the proper service is in the first place.

Network architects have had a long history of dealing with revolutionary technologies that weren't properly marketed, or were too complicated to purchase. It took the industry years to sort out how to deliver VPNs, for example, and VoIP services are no different. AT&T alone offers six different VoIP services, and that's typical among the vendors.Enterprise VoIP services can be divided into transport services, which carry VoIP; and signaling services, which provide higher-layer IP telephony capabilities. VoIP transport services can run over carrier-run IP networks, the Internet, or traditional data services such as frame relay. Carrier-run VoIP networks provide predictable, high-quality voice by running across a carrier-managed IP, IP/Multiprotocol Label Switching (MPLS), or frame relay backbone. Examples of carrier-run IP networks used for VoIP include AT&T's IP VPN and IP-Enabled Frame Relay, Global Crossing's On-net Transport service, and MCI's Private IP.

These VoIP transport services can be delivered as either managed or unmanaged services. As managed transport services, vendors can tweak the underlying network to enhance VoIP capabilities. AT&T's Voice over VPN service, for example, is a managed version of its Network-Based IP VPN service, formerly known as Enhanced VPN (EVPN). The difference is that Voice over VPN lets routers use the Compressed Real-Time Transfer Protocol (CRTP), which drops the 40 bytes used for IP, UDP, and RTP header fields down to four bytes. The service also provides packet fragmentation, which prevents large packets from congesting 64Kbps or 128Kbps access lines. AT&T also offers VoIP with its old frame relay service, called the Managed Router Service. MCI's Private IP doesn't offer CRTP, but does provide packet fragmentation.

Lower-priced offerings are available through corporate Internet-based VoIP services. By locating sites on a single provider's Internet backbone, service providers can deliver better predictability than would be possible across the Internet and at a lower price point than can be had on a privately run network. However, because these are public backbones, SLAs aren't as good as those available on the private IP network. An example of such a service is AT&T's Managed Internet Service with VoIP.

Service providers can also deliver VoIP signaling services. With CPE-based signaling services, service providers locate a telephony server at the customer premises (or a gateway in the case of existing telephony installations). AT&T's IP LAN Telephony Services fall into this category. MCI doesn't offer such a service.

Network-based (or hosted) VoIP signaling services are built around telephony servers and gateways in the carrier's network. MCI Advantage was the first of these services from a major carrier and today runs over MCI's Private IP and Dedicated Internet services. AT&T plans to deliver such a service, but hasn't announced an availability date. Global Crossing offers VoIP Outbound, which provides a network of PSTN gateways that enterprises can use to terminate their VoIP calls. THE VPN SERVICES

Carriers are working to flesh out their VoIP offerings, but in very different ways. MCI's announcement recognizes that the traditional conception of converged WANs was overly simplistic. Converged WAN services originally delivered a "gold" service for VoIP, a "silver" service for critical business applications, and a "bronze" or best-effort service for applications such as e-mail.

However, many companies need to prioritize more than three or four applications on their access lines. In addition, line-of-business applications may be just as important as telephony and need to be treated differently from other applications. MCI responded to this niche by extending its silver service class from one queue with two subclasses of applications to two queues with four subclasses.

Meanwhile, VoIP traffic runs over the gold service class. MCI added a jitter guarantee of 10ms to its gold service in late 2003. The guarantee is comparable to Global Crossing's offering, but is significantly lower than Sprint’s 2ms jitter SLA offered with its MPLS VPN service (see "Sprint's MPLS VPN Service," Product Roadmap, March 2004). The difference likely lies with the port-speeds assumed by each carrier. Sprint assumes a 10 Mbits/s port while MCI assumes a T1 port. The higher the port-speed the lower the transit delay and hence the better Jitter measurements. AT&T does not offer a jitter SLA.

For its part, AT&T has enhanced its VoIP signaling offering, tailoring it to the specific needs of a major niche market, the financial sector. Two new features figure prominently in targeting this industry. A "hoot and holler" feature allows for one-way call broadcasts using IP multicasting, and an "automatic ring down" feature creates instant connections with other users at the push of a button. Neither feature is offered on MCI's service.The other major push for these vendors is their global expansion. Last November, Sprint announced that it was rolling out its MPLS VPN in over 100 countries across Europe, Asia, and Latin America. Global Crossing announced that its MPLS service was available in 50 countries, and AT&T said the same in December.

MCI already offers its VPN overseas and has now added its Advantage service to this category as well. During the first half of this year, MCI will also offer Advantage over its Dedicated Internet service. In the second half, MCI will start offering Advantage over Private IP, first in the United Kingdom and then to the rest of Europe.

The most exciting developments are yet to come. Jon Barnes, MCI's senior manager of Advantage product marketing, says the company will add support for Session Initiation Protocol (SIP) trunking by June. As we've previously noted, the addition of SIP trunking lets IT deploy telephony servers at major sites while relying on the service provider to deliver VoIP to remote offices (see "VoIP Races For the Remote Office," December 2004). The two networks are tied together through a common dial plan and VoIP network. MCI's initial service offering will provide voice transport only. Presence, IM, and other SIP capabilities aren't yet scheduled for implementation.

Executive Editor David Greenfield can be reached at [email protected].