In the March 23, Communications Technology-hosted Webcast on IPv6 provisioning and deployment, experts discussed issues and strategies for making the transition to the latest Internet numbering infrastructure.

The depletion of IPv4 address space remains the main driver for IPv6 adoption, although device management is one reason that Comcast entered this arena.

As for address exhaustion, Incognito Software VP Broadband Technologies Chris Busch said about 8 percent of the IPv4 addresses remain available. (Incognito was the sponsor of the webcast.) At the same time, more than 100 million IPv4 addresses are being consumed per year.

“We have to move on and understand what we need for IPv6, what systems will require, what standards are employed and what clients on the network will need to take advantage of all of the above,” Busch said.

The main cable industry concern is to understand the migration of standards such as DOCSIS and PacketCable. DOCSIS 3.0 was the first standard to specify the use of IPv6 for device management. Yet there is considerable desire to support IPv6 in the more established base of pre-3.0 devices.

On the voice side, cable operators can use PacketCable 1.0 in hybrid mode so the modems can support IPv6, but remain compatible with the legacy eDVA phone adaptors operating with IPv4. When operators move to PacketCable 2.0 they will be able to fully support IPv6 on voice devices, as well.

Comcast and Cox differences

Comcast’s original motivation to deploy IPv6 included improving device management for cable modems. But doing so is no easy feat.

“There is an extraordinary amount of work and preparation that goes into readying a core network infrastructure and back office to support device management,” said John Jason Brzozowski, a Comcast Distinguished Engineer and the MSO’s chief architect for IPv6.

To help reduce the cost of the upgrade, Comcast needed to pay attention to equipment refresh cycles so that upgrades came along with other planned changes in the network. Brzozowski said that after this investment, they found they could also offer IPv6 services to subscribers, as well. In the future, he said that IPv6 could be used to enable video and other interactive services.

Cox Communications had a different driver pushing its IPv6 deployment. Managing cable modems was not as big of an issue, because they use separate private addressing spaces in each system, allowing them to reuse the same IP addresses across its different regional networks.

“The real driver for us was IPv4 address exhaustion,” said Jason Weil, principal architect in Cox’s Network Architecture Group.

Weil noted that customer premise equipment, especially on the retail side, began appearing this year, and that chipsets are also catching up. On the consumer side, the cable industry is communicating CableLabs’ eRouter standard to the IETF as a way to ease the transition by helping to better bridge the two naming systems.

(Brozozowski and Weil were doing just that at an IETF meeting that was occurring at the same time as the webcast.)

Business case

There may be a disconnect between pending IPv4 address exhaustion and activity providing more native IP services, said Busch.

Part of problem is that many operators don’t see the investment of time and money as a revenue-generating opportunity and believe they have enough IPv4 addresses to carry them for many years. True enough on the first count: IPv6 migration is less about making money than assuring continuity of current and existing services as the Internet at large moves to IPv6.

Amidst measurable IPv4 address exhaustion, however, continuity is a legitimate networks ops concern. Going forward, cable operators that lack the ability to support IPv6 could find it difficult to offer mainstream services.

Brzozowski said the primary benefit is the expanded address space. There are potential operational benefits in terms of improving the management of devices. This could lower the human costs of managing the network.

Weil said there are benefits on management. The fact that you can represent all of the cable modems on a single interface means that cable operators will not have to make changes to cable modems on a regular basis.

Provisioning tips

The process of making the transition starts by requesting new numbers from the regional numbering provider, which is the American Registry for Internet Numbers (ARIN) in the U.S.

The more challenging part is planning how to rework network numbering systems and implementing firewall changes to minimize work down the road. You need to decide how to separate the types of traffic based on different devices.

“One of the fundamental aspects of our program at Comcast is that IPv6 cannot adversely affect the existing services that we offer to our subscribers,” Brzozowski said.

Weil said that Cox has been testing different strategies for the transition over the last three years. Operators need to be testing now, because they will find bugs that affect their particular architecture, just as Cox did.

There are different ways to make the transition. One is to support both IPv6 and IPv4, as Cox did. Then there is tunneling IPv6 through IPv4 using generic routing encapsulation (GRE) or IP-in-IP. But Weil said that he prefers MPLS (multiprotocol label switching), which is inherent in the core of the Cox network.

There are many options for routing. Weil said Cox preferred a separate control plane for IPv6 and IPv4 today. Eventually operators will route both using a single control plane and ultimately eliminate IPv4 entirely. But this will be many years away.

“The long term plan is to make v4 go away,” Weil said, “but we have to get all of the content there first.”

With the separate control plane approach, OSPF (open shortest path first) v2 is used for routing IPv4 traffic, and then either OSPFv3 or IS-IS (intermediate system-to-intermediate system) is used to carry the IPv6 traffic. Weil envisions IS-IS being used for both as operators move to a common control plane.

DOCSIS 3.0 introduced support for IPv6. Operators thereafter have ported the IPv6 requirement back to DOCSIS 2.0 + IPv6. This means the same requirement now applies to a subset of DOCSIS 2.0.

As part of the evolution of IPv6 in the cable space, leaders have realized the need for some additional specification to differentiate the control of the devices from the services that run through the devices. “We need to be able to surgically enable IPv6 for device management without affecting other services,” Brozozowski said.

Operators also need to be aware of all of the different network services that leverage the IP address system, including DNS for hierarchical naming, Kerberos for security, SNMP for management, and TFTP for sending new binaries to devices.

Seize the day

The transition is going to be a long, but with proper planning, it does not have to be a painful process. It also will take coordination between cable operators, network equipment and consumer electronics device manufacturers, as well as content providers.

“We need to make sure that the people that build products for subscriber premises and operator networks do pay attention to IPv6, and this doubly applies to people that distribute content,” Brozozowski said. “One of the biggest keys is making sure we have parity in IPv6 for the content we know and love in IPv4.”

The whole process will require up front planning to develop a strategy that meshes well with existing network upgrades in order to keep costs and problems to a minimum. It is also important to keep the entire technical staff apprised of the various changes.

“The requirement for training is something that everyone should be looking at doing,” Weil said. “You don’t want to be on the last day where you are turning on a customer, when you try to figure out how to troubleshoot IPv6.”

It is also important to think about how this will affect the entire cable IT infrastructure, and not just the customer-facing network. “Be aware of the scope of how far IPv6 can reach as you upgrade your desktops and your enterprise back-end solutions,” Weil said.

“Not just the customer facing solutions, but the databases and places where you need to store IPv6 data. This will add a lot of work that needs to be factored in as you go through your migration. “

To listen to the full webcast, register here.

For related IPv6 news, including announcements of the Comcast and Internet Systems Consortium (ISC) release of open source software and Comcast’s 2010 v6 trials, click here and here, respectively. For an overview of IPv6 from Comcast’s perspective, as of September 2009, click here.

–George Lawton

The Daily


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