Can SDN and NFV Work for Mobile Video?

According to practically everyone, video is the fastest-growing and most disruptive of all the Internet traffic sources.  Were it not for video we’d probably not have neutrality debates, and most of the return on infrastructure issues operators are bemoaning would disappear.  And despite the fact that surveys in both the US and Australia have recently demonstrated that online video is not reducing broadcast viewing, we’re going to have more video going forward.  That means handling video might well be the largest issue in networking, and it’s therefore surprising we don’t hear more about using SDN or NFV to improve it.

Part of the video problem is neutrality regulations, which have generally discouraged Internet settlement and special handling.  In the US, the previous FCC Chairman was a fan of the OTT community and reflected his view in a neutrality order that allowed only customer-pays models.  Given that customers demonstrably won’t pay for priority, that has moved video delivery off the table in an economic opportunity sense.

Interestingly, even the original neutrality order didn’t forbid video optimization via SDN or NFV.  Content delivery networks (CDNs) are explicitly not covered by the order, and in any case the DC Court of Appeals vacated the key points because the FCC didn’t have the jurisdiction to apply common carrier rulemaking to a group of players (the ISPs) who they’d previously declared were not common carriers.  The ins and outs of public policy with respect to neutrality are too opaque to judge at this point, but it seems unlikely that a new order would go further than the old one, and so we could reasonably look at how video handling within a CDN might be facilitated by SDN, NFV, or both.

One key point in the discussion is the intersection between OTT video and mobility.  Most of the video growth is driven by mobile devices, and it’s the use of these devices to watch video when a TV isn’t available that’s responsible for the “broadcast-plus” model of consumption.  Mobile networking has promoted a different model of CDN deployment as well as of video viewing.  Classic CDNs peer with access providers (ISPs) and deliver content without all the intermediate handling that traditional Internet delivery would involve.  Most of these are owned by third parties like market leader Akamai.  Mobile CDNs are emerging as operator-driven accommodations to the challenges of delivering mobile video and at the same time preserving mobile bandwidth for other applications.

The technical difference is that mobile CDNs have to be closer to the handset or too much of the mobile infrastructure, particularly critical EPC facilities, are used up before you even get to a cache point.  It’s this deeper mobile CDN caching that could be a target for SDN or NFV.

“Could” is the operative word, because there’s not a whole lot going on to make either technology helpful.  The challenge is the nature of mobile broadband—the user moves around in the course of a video relationship and in IP networks the address of the user determines the point of delivery of the packet.  If a user roams into a cell, the pipeline for that user has to redirect to the cell location or the user’s video is delivered to where they were, not where they are.  That means that in order to make even mobile CDNs work you have to make mobility work with IP.

Evolved Packet Core, or EPC, is what handles this today.  In simple terms, EPC anchors all the mobile addresses for an area in a public gateway (PGW) that then initiates a tunnel to the cells, one end of which is moved by the whole mobility management thing of EPC to reflect user movement among the cells.  One way to resolve the issues with SDN and NFV and video would be to implement EPC, which of course many claim to do.  The difficulty is that they do it by simply executing EPC using hosted technology (calling it NFV) or explicit forwarding paths (calling it SDN) and not by re-framing the whole EPC notion using the new technology.

We could imagine SDN defining a new service model, the “whip”, which is a tunnel that’s anchored at one end and that moves under SDN control at the other to whip among cells to where the user is actually roaming.  We could imagine this model being controlled by hosted functionality.  That could solve the mobility problem.  We could also imagine the dual-stack location-address-and-user-address model proposed by some for the Internet doing the heavy lifting here.  In either case, we’d be decomposing EPC into functions and then optimally implementing them in new technologies, not simply doing a rehash of the old EPC structure using hosted components or explicit paths.

This same sort of thing could help video.  We can put a cache anywhere, but as a practical matter it has to be outside the EPC or it can’t be linked to the mobile user.  If we had NFV-hosted functionality to drive SDN-based “user address space assembly” we could run tunnels from every cache point to the cells directly and have them “join up” with tunnels (“whips”) that represent EPC-controlled sessions.  That would let us cache deeper and more efficiently.

The lesson here is that the challenge of video could be better addressed by simply saying that if SDN and NFV are truly revolutionary, we need to stop applying them simply to create pre-SDN-and-NFV structures.  We need to rethink the problem at the functional level, then solve that problem optimally in the context of our most modern technology choices.

This is another area where NFV could take a lead in the technology evolution of networking.  The challenges for this more modern version of EPC or CDN are more operational than data-plane-technical.  It’s not hard to describe what we want to happen, but it’s challenging to manage the complexity in such a way as to control costs.  Without cost control, it’s doubtful we could apply these new mechanisms because the operators wouldn’t see the return or the users wouldn’t pay the price.

It’s hard, even dangerous, to stick your neck out and suggest that we do something different.  It makes you an enemy of most incumbents in a space, who view change as risk.  We can alienate mobile operators, CDN operators, network vendors, content providers…practically everyone.  But maybe some current alienation is a prerequisite to future progress.