Cisco is remaining tightlipped as speculation swirls around the challenges its next-generation core router will face in the market.

After years of anticipation, Cisco's so-called HFR -- which stands for Huge (Expletive) Router -- will be unveiled May 25 along with a new, modular operating system for the product.

Though Cisco won't provide additional details beyond an executive's confirmation that it will be shown at Supercomm in June, HFR is expected to support at least 640G bit/sec of switching capacity in a full telco rack.

HFR, however, comes two years after rival Juniper Networks began shipping a 640G-bit/sec half-rack system. And Juniper is expected to soon raise the stakes by announcing trial customers for its TX router interconnect, which clusters multiple 640G bit/sec T640 routers together into a multiterabit system.

In addition to ostensibly being late, the rack requirements of HFR are also an issue. Sources say it will require a non-standard 23-inch wide equipment rack as opposed to the standard 19-inch width.

With central office real estate and square footage at a premium, HFR may require a bit more expense and installation disruption than other Cisco and non-Cisco routers.

"It's not NEBS-compliant," says Frank Dzubeck, president of consultancy Communications Network Architects, referring to the spatial and environmental requirements for central office equipment. "Everybody I talk to says [NEBS-compliance] is mandatory, you can't get away from it. You can't go into a [central office]" without it.

HFR's new software may also raise red flags. Speculation has it that HFR and its new modular operating system are undergoing tests at Sprint, and at some visible Juniper accounts like Deutsche Telekom, MCI, and a large Asian carrier -- perhaps NTT. 

New operating system software requires a year, perhaps even two, in production use to prove itself reliable, according to a bulletin on HFR issued by Erik Suppiger, an analyst at Pacific Growth Equities, as well as other sources. This may extend HFR's sales cycle as carriers wait until HFR's operating system stabilizes, the Suppiger bulletin states.

Some analysts view the stabilization process as standard operating procedure and not unique to Cisco.

"Taking a year or two to break in the software is not unreasonable," says Joe McGarvey of Current Analysis. "Avici went through the same thing with AT&T, and Juniper went through the same deal" with its customers.