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Adding IP-over-DWDM and a new type of GMPLS, Cisco hopes to bring the CRS-1 closer to the optical core

Craig Matsumoto

December 5, 2005

4 Min Read
Cisco's CRS-1 Goes Optical

Some of Cisco's ongoing plans for the optical network are getting implemented in the CRS-1 core router, as the company today plans to introduce new DWDM optics for the box as well as support for Cisco's version of generalized MPLS (GMPLS).

Cisco is announcing the developments in conjunction with its annual analyst conference, which begins tomorrow in Santa Clara, Calif.

Buried in the announcement is the fact that {dirlink 5|38} (Nasdaq: CMCSA, CMCSK) has become a CRS-1 customer. The cable operator hasn't formally announced it's using the router, but an official is quoted in Cisco's release saying Cisco's new DWDM interfaces represent "key reasons for our selection of the CRS-1."

"We believe the CRS-1 can be the foundation of our NGN strategy into the next decade," says John Leddy, Comcast vice president of network and transport engineering, in an LRTV video produced for Cisco. (See IP Routing for Next-Generation Networks.)

Comcast's decision isn't that much of a surprise, as the cable operator is building a next-generation IP network that already incorporates Cisco's BTS 10200 softswitch and Call Session Control Platform. (See Cisco's CRS-1 Gets Edgy.)

Cisco's principal announcement for the CRS-1 concerns a pair of cards with high-speed DWDM optics. This opens the possibility of the box launching IP traffic onto DWDM wavelengths directly, bypassing the Sonet layer.

One card sports a tunable, single-port, 40-Gbit/s interface that can connect to a 10-Gbit/s optical infrastructure. Cisco previously demonstrated a 40-Gbit/s interface that used StrataLight Communications technology to run the traffic on a 10-Gbit/s optical network; officials wouldn't comment on whether this new card uses the same technology. (See StrataLight Powers Cisco's OC768.)

The other card provides tunable WDM optics for 10-Gbit/s Ethernet, using digital wrapper technology, per the International Telecommunication Union (ITU) G.709 standard, to link the traffic to Sonet operations, administration, and maintenance (OAM) that Ethernet wouldn't normally have.

IP-over-DWDM is something Cisco has talked about for a while. The idea complements Cisco's strategy to use the same pluggable optics on its routers and on optical equipment like the ONS 15454. (See DWDM Goes Pluggable.)

The idea was kicked around circa 1999 as a means of "collapsing" the network, removing a layer of Sonet equipment to save costs. DWDM vendors such as Ciena Corp. (Nasdaq: CIEN) would seem to have the most to lose in such cases. But Ciena says it's ready for the trend once it starts, as equipment like that company's CN 4200 can be used to put different service types onto DWDM wavelengths. (See Ciena Claims DWDM Coup.)

"You still need that WDM network to carry your traffic," says Vinay Rathore, director of segment marketing for Ciena. "The DWDM thing they've gotten rid of is just the transceiver, not a separate box."

Rathore also contests the notion that entire systems would be removed from the network this way. In many cases, IP-over-WDM just amounts to moving a transponder from an optical box into the router, he says.

GMPLS redux
As for what to do with IP-over-DWDM, Cisco is adding to the CRS-1 a new version of GMPLS, the set of protocols aimed at letting routers request bandwidth from the optical network.

The hangup with GMPLS was that carriers didn't want to reveal their optical networks to other carriers' routers. So, GMPLS fragmented into two models -- "peer," where routers get full visibility into the optical network, and "overlay," where routers can place bandwidth requests but don't get to see the topology of the optical network. (For a history lesson in GMPLS, see the 2002 report, Optical Signaling Systems.)

Cisco has created a compromise called the Segmentation Model of GMPLS, or S-GMPLS. The optical network owner gets control over how much visibility routers get, with the option of giving the router full visibility.

"You can think about it like service providers that are peering -- you can advertise routes," says Mike Capuano, a Cisco senior marketing manager.

GMPLS is represented by at least a half dozen standards from multiple groups, including the Optical Internetworking Forum (OIF), which is pitching an overlay model called Automatic Switched Optical Networks (ASON).

Cisco is adding S-GMPLS to the fray, having filed an Internet Engineering Task Force (IETF) draft in July titled Operational, Deployment, and Interworking Considerations for GMPLS.

S-GMPLS combined with IP-over-DWDM creates this scenario: Cisco's CRS-1 could connect directly to reconfigurable optical add/drop multiplexers (ROADMs), such as Cisco's 15454, with therouter able to assign wavelength adds and drops on the ROADM. "In general, to have a whole solution like that from a single vendor is really valuable," says Scott Clavenna, Heavy Reading chief analyst.

One question facing S-GMPLS is whether carriers are that interested. GMPLS was intended as a way to create a dynamic optical core, with wavelengths being brought up as routers needed them -- but carriers still don't show much interest. "They still think of the core as more of a static thing," Clavenna says.

Cisco officials say they're hearing demand for GMPLS or similar functions, pointing to GMPLS trials conducted in June with {dirlink 5|135}. (See Cisco, NTT Demo GMPLS.)

— Craig Matsumoto, Senior Editor, Light Reading

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About the Author(s)

Craig Matsumoto

Editor-in-Chief, Light Reading

Yes, THAT Craig Matsumoto – who used to be at Light Reading from 2002 until 2013 and then went away and did other stuff and now HE'S BACK! As Editor-in-Chief. Go Craig!!

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