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MPLS knows best?

Sat, 07/31/2004 - 8:00pm
Karen Brown, Senior Editor

Long a standard on major communications backbones, Multiprotocol Lable Swithcing is now making inroads into cable networks. It could have a
potential role in a future converged, all-IP cable network,
but there are obstacles standing in tis path as well.

It's been guiding traffic on major Internet backbones for years, and now Multiprotocol Label Switching (MPLS) may be cutting a path to a cable network near you.

Cable operators appear to be looking at MPLS primarily to offer valuable enterprise services, including dedicated bandwidth and virtual private networks. But it may also play a role in a longer-term cable future where Internet Protocol voice, video and data all flow down a single, unified cable pipe.

MPLS is a sort of fusion of dedicated circuit ATM sensibilities with the homogeneous mass-routing skills of Internet Protocol. And, being multiprotocol, it can handle IP, frame relay or ATM traffic. At MPLS' core are label switch routers, which set up paths for packets based on what the data is and how fast it has to get to its destination. These label switch paths can be assigned prior to a known data transmission or when the router detects the packets' flow.

The label switch router acts like a virtual post office, giving data packets labels loaded with destination information and delivery priority before firing them off into the network. Routers in the network push along the data based on the destination information in the labels, and they can give speedier delivery to the higher-priority traffic. This process is faster than the first-come, first-delivered IP world, where routers must stop and look up the IP address of the next node in the delivery chain before sending the packets on their way.

Using MPLS, operators can create dedicated virtual private network connections, but, unlike standard ATM circuits, these connections only activate when there is data to be sent. That gives the network operator greater bandwidth flexibility.

"That's the real value of MPLS...You can establish this path, end-to-end, and it will set up the appropriate QoS end-to end," says Jeff Walker, senior director of marketing for Motorola Broadband's network infrastructure solutions business. "The intervening routers or ATM switches don't have to look deep into the packet. They can look at the label and say, 'Oh, I see that this goes into that label switch path, which has already been specified that it needs this amount of bandwidth and this type of latency'."

Cablevision Systems Corp.’s Lightpath enterprise unit has put
MPLS to work in its core, and future plans will extend
that to the access portion of the network.

An enterprising technology

Although not well known yet, MPLS technology is cutting a path into cable networks, primarily through enterprise services. Charter Communications started using MPLS in its network two years ago, and that has led to an MPLS enterprise VPN service rolled out in its Western and Great Lakes systems. The service will soon expand to its Midwest division, according to Mike Emendorfer, Charter's director of advanced network technologies.

"We've enabled these services as a frame relay replacement, using a DOCSIS cable modem for the CPE and a CMTS for the provider edge," he says. "We are delivering services to customers that have both cable modems at sites as well as fiber at sites."

The MPLS service is still in its early stages, but Charter hopes to eventually widen its reach, possibly using it to create a dedicated VPN channel for all voice services, for example.

"Basically, what we have already done is enable it in the access layer," Emendorfer says. "Over time, we are going to extend use of this technology beyond a multi-state backbone ring to across our core network."

Meanwhile, Lightpath, Cablevision Systems Corp.'s telco enterprise services subsidiary, recently jumped into MPLS in a big way, installing Cisco Systems Inc. gear and activating the technology in the core of its New York City-centric network. Cablevision also plans to soon extend that to the network edges. Doing so will allow Lightpath to unify its ATM, frame relay and TDM voice traffic on one network that is much easier to maintain, according to Brian Fabiano, senior vice president of network services.

Bandwidth efficiency also is a strong selling point. Given that label switch paths are activated only when needed, Lightpath no longer has to maintain fixed-bandwidth circuits.

"It's going to clearly optimize my bandwidth, rather than having to provision bandwidth in certain markets to deliver certain services–and not knowing if the demand would materialize or not," Fabiano notes. "I can shift my bandwidth within the network now and really put Lightpath where it needs to be given customer demand."

MPLS also will allow Lightpath to roll out new services, such as virtual private Local Area Net-work connections, 10/100 Ethernet-over-IP, Voice-over-IP and storage area networking–not to mention service packages based on service level agreements with the customer, Fabiano says.

Ethernet "has always been a best-effort technology," he points out. "We're now providing resilient Ethernet services, and now being able to offer quality of service, we can tell our customers depending on what services they have and what priorities they view on that, that we can set up a VPN that gives their voice traffic the highest priority."

Cox Communications Inc. also has moved into MPLS. For about six months, it has used the technology for traffic engineering on its backbone, directing IP packets over preferred routes when data traffic jams occur, says Randy Kinsey, manager of network engineering and architecture. Starting with the traffic management element serves as the classroom for Cox as it learns how to set up and run an MPLS-driven network.

"It's for the engineering group and the architecture group and the operations group to get it launched, get it deployed, get it understood and understand how it behaves and how it works–how all of the platforms handle it," he says. "We are a multi-vendor network, so each box has to run it and all of the protocols associated with it."

Motorola’s BSR64000
Motorola’s BSR64000
Short-term, Cox is looking at MPLS to support extended commercial services, banking on the technology's VPN and dedicated bandwidth capabilities to add to quality-of-service elements already deployed on the network. As yet, Cox has set no timeline for launch of such a service.

"That's what I think it (MPLS) provides us–the ability to take our network and make it look like a dedicated transit pipe or some sort of dedicated transport pipe to a customer," Kinsey says.

In the gear

Elsewhere, another indicator that MPLS is starting to tunnel into cable networks is the fact it's showing up in cable-specific gear.

Motorola's BSR64000 cable modem termination system (CMTS) already has built-in MPLS capabilities, and the gearmaker is seeing U.S. MSOs start to take advantage of that, mostly in fielding enterprise services, according to Walker.

Cisco’s uBR10012
Cisco’s uBR10012
Cisco, meanwhile, has also built MPLS support into its uBR7246VXR and the uBR10012 CMTS units.

"Our selling point, if you will, is we have an intelligent CMTS that is a Layer 3 box, and you can basically set up all of these (VPN) tunnels from the CMTS," says John Mattson, Cisco's director of marketing for cable products.

Fujitsu showed off an MPLS switch tied to its optical Ethernet gear, using MPLS technology supplied by partner Atrica Inc. John Cupit, Fujitsu's senior network architect and product evangelizer, says the MPLS switch is going into trial with a major MSO, possibly by September.

"We feel that there is a significant role MPLS has to play in the migration not only of MSO networks, but in all carrier networks," he says.

Grand unified pipe

With its ability to mix all kinds of data and deliver across multiple IP networks, MPLS may also play a role in the converged all-IP Next Generation Network Architecture (NGNA) now being sketched out by several cable companies, including Cox.

"So with the cable companies going toward the triple play, trying to do voice-over-IP, data and video all on one network–and specifically because a lot of them are now using IP as a technology for delivering video–it does make sense to start using MPLS in some portions of their network," says Ramin Farassat, director of marketing at RGB Networks. "Not necessarily that they would push MPLS down to the home, but in the center of the network for the distribution of the different types of content."

Motorola's Walker, meanwhile, says industry brains are thinking about MPLS in an all-digital network, but, he adds, that may not include high-volume data services. In some cases, cable operators may opt to keep dedicated Gigabit Ethernet connections for consistently high-volume traffic generators such as video-on-demand, rather than flooding the unified network with this traffic.

"When you are starting to talk about Gigabits of traffic–and multiple Gigabits of traffic–it almost becomes irrelevant to put it into individual label switch paths, because at that point you are probably going to dedicate a 10-Gigabit link or a Gigabit link to just handle the video traffic," Walker says.

Mattson, too, acknowledges that high-volume traffic may be separated from other data traffic, but he still thinks MPLS will play a big part in the overall network.

"I think both are going to happen," he notes. "And again, I think the end game is the integrated network–IP everything, IP everywhere. But you always end up with a mixture of old stuff and new stuff."

Limits

Back in the present, there are still hurdles to overcome before MPLS becomes mainstream. To begin with, it places a heavy processing demand on routers, and as in the early days of MPLS integration on major backbones, there could be router meltdowns.

"It really increases the requirements on the switches," Farassat says. "If you have a smaller network, it really wouldn't be an issue. But if you are looking at a very, very large, multipoint network with lots of devices and lots of users on the network, then you are going to need a very powerful switch."

Walker agrees.

"In the United States, most of the cable operators are still saying, 'Yeah, I really want MPLS on my systems, and I'm looking at it for my metro network. But I'm not ready to do it today'," he says. "Because it requires all of the routers in your network to support MPLS, and they are just not there yet."

Similarly, others doubt whether end devices such as cable modems and set-tops can support MPLS, given their relatively limited processing capabilities. Mattson says it is possible, so long as the devices are DOCSIS-driven and are backed up by an MPLS-capable CMTS unit.

"The end device doesn't need to be a router–it just needs to speak IP and it needs to have a MAC address," he notes. "So as soon as you start putting cable modems in set-top boxes essentially, and as soon as you start being able to assign IP addresses to set-top boxes, then you can really start doing all of this stuff," Mattson says.

On that point, Cox does have plans to extend its MPLS capabilities from core routers closer to the edge, but Kinsey voices some doubt whether that will reach as far as the CMTS in the headend.

"There is a lot more horsepower in a CMTS, but there are already a lot of things going on inside of a CMTS. It is an additional protocol stack that has to be added to the device," Kinsey says.

And there is a question as to how much quality of service would be needed, given QoS is a key plank in the DOCSIS 1.1 and DOCSIS 2.0 specifications.

"Would it really matter to have full MPLS capability on the DOCSIS modem?," Farassat asks. "The question would be, would you have other devices that are going to be sitting behind your DOCSIS modem that are going to be needing a higher quality of service?"

Nor will MPLS be funneling a lot of mainstream VOD or broadcast video in the near future, because to do so, the video needs to be in IP format. With most video still running in MPEG-2, they would have to find a way to translate it to IP in the network.

"Most MSOs that I've talked to are not that enamored of streaming video to PCs yet," Mattson notes. "Long-term, that may be something that they want to do. But they are usually looking for the lowest-hanging fruit, and the lowest hanging fruit is commercial services."

Video could come into play there, however. For example, Charter is looking at an enterprise video multicast service supported by MPLS, and "we've already been in discussions with a few potential customers for leveraging that technology," Emendorfer says.

Another obstacle is the sheer amount of education the cable operators have to undergo to understand the MPLS technology. It isn't an easy lesson plan–Kinsey recalls a Cox engineer who recently quipped that MPLS stands for "Making People Look Stupid."

"There is a complexity level there. It takes a lot of research," he says. "My group handles all of that, and one of the things we are very big on is doing a lot of testing in the lab before we deploy it."

Mattson, too, notes MPLS may be daunting to learn, but the benefits, particularly in enterprise services, are still a lure for cable operators.

"It's like anything new–because it is new it is scary and it is a little complicated at first," Mattson says. "If you are just trying to nail up one or two virtual private networks, it seems easier to kind of do it the manual way. But as soon as you start adding the third one and the fourth one, the network complexity eats you alive. So all of a sudden that little bit of boning up you need to do up front becomes worth your while."

In that process the vendors play a vital educational role if they want to be part of cable's MPLS future, according to Fujitsu's Cupit.

"This is not a situation where you can wait and allow the cable companies to become educated and then think you have an opportunity to respond to an RFP," he notes. "The winners from that standpoint in this particular game are the ones that are engaged today and are actively leading efforts to educate the MSOs."

Despite the obstacles, it looks like MPLS is starting to pop up on cable's technology radar. Even if they at first limit it to just enterprise services, that does open the door, Mattson notes.

"Once they get there and once they convert video onto IP all the way out to the home–which I think they will, ultimately–MPLS will be a big part of that," he says. "I think the nice thing is they can go ahead and implement it today and use it for commercial services initially and the infrastructure is there. Once they want to do converged IP video, it's all there."

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