MPLS readies networks for user boom

Part One: MPLS facing slow adoption, despite flurry of market hype | Part Three: MPLS lays foundation for new VPN services

Proponents of Multi-protocol Label Switching (MPLS) say this technology's traffic engineering capabilities can help service providers meet this challenge, ensuring that integrated voice/data, videoconferencing and other new services receive the amount of bandwidth they require.

"Traffic engineering helps operators manage their networks better," says Eric Peterson, director of protocol development for Unisphere Networks, which makes MPLS-enabled edge routers. "It's intrinsic to the ability to scale IP networks."

Even though wholesale adoption of MPLS has been slow (see Part 1 of this series), those using the technology find traffic engineering can provide immediate benefits.

Traffic engineering refers to the ability to explicitly steer traffic through a routed or switched network. In MPLS, this is accomplished by labeling IP packets with forwarding information that directs traffic over an explicit path and forwards it quickly without requiring routers to perform a deep packet inspection at each hop.

MPLS is in contrast to routing with an Interior Gateway Protocol (IGP), which requires this deep packet inspection and forwards packets based on the constructs of the particular IGP, be it Routing Information Protocol (RIP), Border Gateway Protocol or Open Shortest Path First (OSPF).

RIP will route based on the least amount of hops and has a 15-hop limit. OSPF may look for the least expensive or higher bandwidth route.

These IGPs will use the same route for the same destination IP address, unless a link or links in the route fail. Even if the route's congested, the packets will be sent to them.

By engineering traffic with MPLS, service providers say they can build bigger networks by making more efficient use of otherwise underused links and avoiding the latency involved in hop-by-hop packet inspection.Quality of service (QoS) or service-level guarantees can be ensured by explicitly directing traffic onto the fastest, least congested or shortest paths.

Global convergence on MPLS

Masergy Communications, an emerging global carrier, is using MPLS's traffic engineering capabilities to scale its network and deliver QoS.

The carrier turned up MPLS-based services a month ago that converge voice, video and data over a single network.

The services include Internet access with prioritization of the traffic, private point-to-point links based on MPLS, IP telephony and IP video.

"It's a little bit more than [traffic engineering] because it allows us to overlay multiple logical topologies on the same infrastructure" of backbone trunks and label switch routers, says Rick Wilder, principal scientist at Masergy.

MPLS lets Masergy overlay a separate mesh network on top of its Internet service infrastructure to deliver the private point-to-point link service, Wilder says. MPLS labels let the carrier differentiate traffic (and service), grant it different levels of priority, and steer it onto different paths - virtually creating a new network using the same equipment and infrastructure.

"There are big gains there in terms of cost of the actual equipment and bandwidth, but also in terms of complexity and management of all the devices," he says.

"If you have the ability to do those overlays using the same pieces of equipment, you've got that much less to configure and manage," he adds.

Wilder says MPLS traffic engineering is going to be important to Masergy and other carriers looking to offer a new generation of flexible services.

"It's what enables us to have the range of service offerings that we can roll out," he says.

Local convergence on MPLS

On a smaller scale, Westelcom, an upstate New York competitive local exchange carrier, is serving 15 sites with MPLS-based integrated voice/data access services. Westelcom is focused on small-and midsize-business customers, and average deployments are six to eight voice lines, plus best-effort asymmetric DSL data services.

In addition to providing traffic engineering and QoS for voice, MPLS enables Westelcom to reduce cost, simplify its network design and operations, and reduce the amount of equipment it requires in its central office and collocation sites, says Eric Kreckel, corporate engineer at the carrier.

Using MPLS access devices from Integral Access saves Westelcom from purchasing separate DSL, time-division multiplexer and ATM aggregation gear and routers, Kreckel says.

"[Traffic engineering] was one of the factors in the decision-making process" to implement MPLS, Kreckel says.

"The service also had to be affordable. We had to differentiate it from our competitors, be a little bit more flexible and give [customers] different options than other people could," he adds.

In the Westelcom network, voice is digitized and packetized using the ITU G.711 standard, Kreckel says. MPLS takes the G.711 data frame and prepends a "small" MPLS label on it, which makes the packet size 78K bytes, instead of the 80K to 100K bytes of a voice-over-IP packet with real-time, real-time control and point-to-point protocol headers, he says.

"A [voice-over-IP] packet has a heavy packet tax on it after you add those headers," Kreckel says, referring to the increased processing overhead and segmentation framing, and associated delay with the larger packets.

The MPLS label also signifies that the voice packet has the highest bandwidth priority and steers it through the network accordingly, Kreckel says.

"It also does all the other things that QoS requires, such as segmentation and prioritization of the other traffic flows going across the system," he says.

MPLS let Westelcom tap its expertise in IP routing and Internet service provisioning without having to retrain people in ATM, which is renowned for its traffic engineering and QoS characteristics. But MPLS lets Westelcom avoid ATM without sacrificing a lot in the way of QoS, Kreckel says.

"Really what it came down to is [MPLS] could do everything that we wanted, plus it came in at a much more competitive price point for doing that, as opposed to an ATM-style system," Kreckel says. "I'm not going to go so far as to say you're going to get everything that you get with ATM . . . but we get what we need out of it."

Next week: A look at MPLS-enabled VPNs.

Contact Edge Managing Editor Jim Duffy

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Part 1: MPLS facing slow adoption, despite flurry of market hype