It's not tough to spark a shouting match between MSOs and telcos about whose IP pipe is bigger. (See Is Cable Faster Than FiOS?)
But which pipe is better? Ultimately, it's not just quantity, but quality, that matters.
At least that was the argument of Jay Rolls, vice president of technology at MSO Cox Communications Inc. , during a discussion at The Cable Show earlier this month.
In particular, Rolls pointed to the Docsis media access control (MAC), the Layer 2 protocol that enables dynamic quality of service (QOS) capabilities for cable modem networks, among other functions.
"It's a powerful protocol for service differentiation. We haven't fully started exploiting that yet," Rolls said.
Cable's MAC attack is well underway, though. MSOs have widely deployed a PacketCable infrastructure that leverages the Docsis MAC protocol (versions 1.1 and above) to deliver lifeline IP phone service. And over the last year, they've started using the knobs available in Docsis to enhance cable's broadband Internet offerings.
At the top of the list is the Comcast Corp. (Nasdaq: CMCSA, CMCSK) "PowerBoost" offering. First deployed in June 2006, PowerBoost offers on-the fly double-speed bursts during large file downloads, up to 12 Mbit/s for subscribers to the MSO's 6-Mbit/s broadband service, and 16 Mbit/s for 8-Mbit/s service customers. Think of it as an automatic "super-size" option. This month Comcast activated PowerBoost in the upstream direction as well. Bursts of up to 2 Mbit/s are available when uploading or emailing large files, such as photos and videos.
Cox piled on last month too, more widely rolling out its own version of the downstream PowerBoost feature to its cable modem customers. Cox's Rolls says PowerBoost is "a Docsis protocol parameter setting" that temporarily uncaps the modem, providing access to additional bandwidth.
In Europe, cable operator UPC Broadband is now delivering lifeline IP phone service via SIP (Session Initiation Protocol) by leveraging the dynamic QOS capabilities of Docsis. Like many international operators, the MSO is eyeing "wideband" capabilities in Docsis 3.0 that can deliver 200 Mbit/s of downstream capacity (using four 8MHz channels with 256 QAM).
"Combining that [Docsis MAC] with wideband is a powerful differentiation. Against fiber, it comes down almost to a smart pipe versus dumb pipe story," Rolls contended.
Of course, there's no reason telcos can't take advantage of Docsis, too.
Indeed, at the Society of Cable Telecommunications Engineers (SCTE) Conference on Emerging Technologies back in January engineers from Cisco Systems Inc. (Nasdaq: CSCO) presented a paper that proposed porting the Docsis MAC to GPON and EPON. The idea is that MSOs opting to deploy FTTH would be able to use common management and service layers across both their HFC and fiber access networks. But, such a move would mean telcos would have access to the same QOS features as MSOs. So much for the big MAC edge.
Does Docsis over fiber sound crazy? Maybe not. Docsis has already leaped beyond HFC. WildBlue Communications now uses the protocol in its satellite broadband service. And broadband wireless players like Ireland's Digiweb Ltd. have deployed Docsis over the air, too. Why not add fiber to the Docsis diet?
EPON/GPON have their own solutions to QoS. GPON has its roots in ATM and so it has a fairly complex queuing structure (you can sense the traces of ATM VC/VP even in the non-ATM GPON) and is not that different from DOCSIS. EPON is more of an Ethernet QoS model with relative priorities as opposed to separate flows, although flows can be modeled as well.
In the paper I presented for SCTE/ET 2007 (which is referenced here) I outlined two options : DOCSIS management over PON, or DOCSIS MAC over PON. My favorite approach is the DOCSIS MAC *management* (not MAC L2) over PON, in other words use PC/PCMM, DOCSIS provisioning, DOCSIS IPv6 registration etc etc over either EPON/GPON (which maintaining the EPON/GPON hardware and L2) to manage a PON network. In such an architecture the DOCSIS definitions of QoS are mapped to EPON/GPON primitives.
I think that for the case of tier 2/3 teclos, DOCSIS management over PON might make more sense then teclo style management because I believe there are more off-the-shelf solutions in cable (because of cablelabs and the world wide, cross MSO, standards for management) then in telco land.
What the QoS capabilities of BPON or GPON are? The cable guys are pounding their chest saying how great their protocol is. I saw no question or commentary on how FTTH works in this regard.
So, is DOCSIS over fiber possible? Yes. Does it provide advantages over GPON? Well, umm...if you think you need to be looking at your MAC to debug networks then I suppose. Other than that, no there are the same or more QoS capabilities in the PON MACs.
But if the cable guys need to be putting MAC monitoring out there to diagnose their network, perhaps you should ask Verizon if they have ever had to do this.
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