CableLabs this month took some key steps forward on the Data Over Cable Service Interface Specification 3.0, the next-generation technology standard that promises to boost bandwidth, increase security and provide greater flexibility for multiple-system operators to deploy data services.
The International Telecommunication Union, an organization that establishes worldwide standards for communications technologies, “consented” to adopt four CableLabs-developed specifications related to DOCSIS 3.0 at a technical meeting in Tokyo the week of Oct. 2. The ITU's blessing provides an additional assurance to manufacturers and cable operators that DOCSIS-based technologies will be interoperable everywhere in the world, said Greg White, CableLabs' lead architect for broadband access.
The four specs are:
DOCSIS Timing Interface: A specification required for Modular Cable Modem Termination System (M-CMTS), a central piece of DOCSIS 3.0 that decomposes headend functions into separate components for more efficient operation. The DOCSIS Timing Interface (DTI) synchronizes components in the M-CMTS. White said the interface is version-agnostic and can work with vendors' DOCSIS 2.0-based MCMTS offerings.
Downstream External PHY Interface (DEPI): This defines the actual data path between the M-CMTS core and the edge quadrature-amplitude modulation (EQAM) component.
Downstream RF Interface (DRFI): This defines the physical characteristics for an EQAM device. The main new feature provided by DRFI in DOCSIS 3.0 is the ability to have multiple channels per physical connector. In the past, White said, every downstream QAM channel required a separate physical connector; now an EQAM or an integrated CMTS can have multiple channels over a single physical connector. In addition, DRFI allows multiple QAM channels to be bonded together to boost bandwidth. The specification doesn't place any limit on the number of channels that may be bonded: “It's up the vendor to decide,” White said.
Layer-2 Virtual Private Networking: Allows cable operators to create a secure Ethernet tunnel over a DOCSIS system. The specification uses the existing encryption tools in the DOCSIS; the current version of DOCSIS, 2.0, uses the 56-bit Digital Encryption Standard (DES). DOCSIS 3.0 requires the much stronger 128-bit Advanced Encryption Standard (AES).
White expects that the ITU study group that governs cable specifications will adopt the other DOCSIS 3.0 components — the physical layer specification, the MAC and upper-layer protocols interfaces, and the security specification — at its next meeting, tentatively scheduled for June 2007.
Other DOCSIS 3.0 specs still in development by CableLabs include the Operation Support System Interface (OSSI) and the e-Router spec, an optional component that would route between IPv4 and IPv6 networks.
