Virgin Media should reconsider its IPv6 DS-Lite plans for the UK
Virgin Media’s UK IPv6 plans have been mostly surrounded in mystery or the rare insightful public statement that gets released through the years. As a Virgin Media customer myself, it is something that I have followed with keen interest.
As early as March 2010, a post on Virgin Media’s community forum about IPv6 support was born. Today, that forum post has amassed over 100 pages of talk and discussion about when is Virgin Media going to roll out IPv6 to it’s customers. We are still waiting for that answer today. The consistent line has always been “when we feel the need for it”.
Virgin Media IPv6 timeline of events
A brief history of the IPv6 story with Virgin Media.
- March 2010: The IPv6 mega thread on the Virgin Media community forums was born.
- October 2014: First appearance and presentation at the UK IPv6 council.
- September 2015: Second appearance at the UK IPv6 council.
- August 2017: ISPreview reveals there is a “secret” IPv6 trial for 100 members of Virgin Media’s own staff. The first hint of serious activity related to IPv6 beyond Virgin Media’s own network engineers and testnet.
- February 2018: Liberty Global released some interesting information about Virgin Media and it’s plans for DOCSIS 3.1 and IPv6 adoption. At this point it became known that Virgin Media UK had chosen Benu Networks DS-Lite solution for their IPv6 rollout.
- June 2018: A wider customer trial was reported to be underway and judging by the APNIC IPv6 stats for Virgin Media’s AS number during that period, this seemed to involve a sizable amount of IPv6 testing. Granted, not all of numbers may have been residential broadband customers, but none the less there was all of sudden a lot of IPv6 traffic being recorded when there was pretty much zero from Virgin Media prior.
- December 2018: Third appearance at the UK IPv6 council, with some additional information about the wider IPv6 test currently happening and further information about DS-Lite. Hints of an IPv6 rollout in 2019.
- 2019: No IPv6 rollout happens. IPv6 activity on the Virgin Media AS goes quiet.
- 2020: Nothing has changed thus far.
One thing that was becoming apparent was Virgin Media we’re testing an IPv6 deployment based on the transitional technology DS-Lite.
Now I’m not a networking expert and don’t hold any fancy degrees or qualifications on the subject. I’m a Web Developer which as a general by-product of my profession is exposed to various sysadmin/technical areas which I have reasonable knowledge in. So quite frankly, you could say I have no place to comment on this, but your still reading this, so like me you are likely interested in Virgin Media and the IPv6 story too.
The issues with DS-Lite from a consumer basis
The apparent choice of DS-Lite immediately got the attention of a few tech news outlets and groups of more technical customers. Knowing some of the limitations and problems DS-Lite can/could/would cause, concerns we’re immediately voiced.
One key element that became apparent was you would need to stop using modem mode to even be able to be part of the trial. (I wasn’t part of it, because the only way you’ll get me off modem mode is by taking it from my cold dead hands!). Modem mode being the lifeline for more technical customers basically telling Virgin Media supplied router/modem (Super Hub) to get out of the way, shut off all routing functionality and instead simply provide an external IPv4 address to another router through it’s WAN port. Avoiding the double NAT problem. I am one of those customers, who chooses to use routers that support firmware like DD-WRT or OpenWrt, because frankly, the Super Hub lacks any useful features and I like tinkering with networks. Nerdy.
With DS-Lite IPv6, modem mode “doesn’t exist”. The main reason for this is because DS-Lite itself is not widely supported in a lot of routers. Most consumer routers won’t have support for it now and probably won’t in the future. As far as I know, OpenWrt can support DS-Lite through additional packages with opkg ds-lite but it isn’t installed by default and as far as I can tell DD-WRT doesn’t have any native support for it. There may be some enterprise kit that might as well, but the standard itself doesn’t have wide support in “off the shelf” routers. So unlike modem mode for IPv4, you can’t just simply pass over the DS-Lite IPv6 prefix in the same way.
Now, you could argue you don’t need modem mode to use DS-Lite and the IPv6 prefix delegated to you. Correct, you don’t. If you know what you are doing you can have multiple routers in a network and have your own router in behind the Super Hub and take advantage of IPv6 prefix delegation which could pass down a usable prefix you can then broadcast to your LAN something like a /61 (assuming you get a something like a /56), however it’s more complicated to achieve compared to the IPv4 modem mode
The other key issue with DS-Lite is while you get a native IPv6 address, you won’t have any native IPv4. Instead this is provided through CGNAT a technology which is a big plaster over the current internet. The description of DS-Lite from Wikipedia provides an overview of how IPv4 works under this technology.
Dual-Stack Lite technology does not involve allocating an IPv4 address to customer-premises equipment (CPE) for providing Internet access. It is described in RFC 6333. The CPE distributes private IPv4 addresses for the LAN clients, according to the networking requirement in the local area network. The CPE encapsulates IPv4 packets within IPv6 packets. The CPE uses its global IPv6 connection to deliver the packet to the ISP’s Carrier-grade NAT (CGN), which has a global IPv4 address. The original IPv4 packet is recovered and NAT is performed upon the IPv4 packet and is routed to the public IPv4 Internet. The CGN uniquely identifies traffic flows by recording the CPE public IPv6 address, the private IPv4 address, and TCP or UDP port number as a session.
Source: Wikipedia
The major sticking point here is not having native IPv4 and instead your external IPv4 traffic coming from a CGNAT gateway and not your CPE (Customer Premises Equipment). Key functionality that we’ve all grown up with breaks under DS-Lite. Including:
- Native IPv4 that is routed directly to your CPE is no longer provided.
- Port forwarding for any IPv4 client will no longer work because of CGNAT.
- Any NAT forwarding or similar rules for a IPv4 client will not work (as above).
- For gamers, get ready to see “strict NAT type” being reported.
- 1:1 connectivity is no longer possible because of CGNAT.
- P2P applications or software using uPnP under IPv4 will not work.
- VPN tunnels are likely to be broken if they lack IPv6.
- Broadband monitors e.g. thinkbroadband.com (we love monitoring the latency issues on the Super Hub 3 so much right?!).
The list goes on…
The reason for this is because under DS-Lite you will be sharing an IPv4 address from a pool with other customers. DS-Lite gives you native IPv6 connectivity but IPv4 traffic still needs to be passed (because we are no where close to an IPv6 only world), so this is done through 4in6. IPv4 traffic in your network will get in encapsulated in IPv6 data packets and use a local IPv4 address space which ultimately gets routed to a CGNAT gateway which then decides how to deal with the IPv4 packets to route them out to the wider internet. The big problem, you don’t have any control over the IPv4 side anymore. Hence why all your IPv4 configuration that might be happening behind your network now is probably broke under DS-Lite.
CGNAT isn’t anything new though, it is common place on mobile networks and has been in use for years.
Liberty Global and IPv6
Liberty Global acquired Virgin Media in June 2013, they are the parent company of Virgin Media, formerly NTL/Telewest. Liberty Global has network deployments in many countries across the world with IPv6 already. A slide from the 2018 annual UK IPv6 council meeting which Virgin Media were in attendance of, shows that Liberty Global has IPv6 deployments in various countries including Ireland, Switzerland, various EU countries and others. Their track record of deploying IPv6 has actually been quite impressive. The map below, not intending to be a political statement, shows the United Kingdom in red meaning to indicate it doesn’t have an active IPv6 deployment currently. Sounds familiar.
Source: https://www.ipv6.org.uk/wp-content/uploads/2018/11/LG-Virgin-IPv6-Rollout-UK-IPv6-Council.pdf
The full slide deck provides some basic information around the reason for Virgin Media using DS-Lite and the general overview of how it works. The main reasons for this seem to be the following:
- Common IPv6 deployment method used by Liberty Global, so their networking teams have familiarity with deploying DS-Lite.
- Support for IPv6 and DS-Lite is present in the Super Hub 3.0 firmware, although disabled in production by the sounds of it (you can look at the base.js file present in the Super Hub 3 firmware to find clues).
- Cost effective solution for Virgin Media.
- Resolves the IPv4 exhaustion problem, because everyone goes through CGNAT gateways and is no longer allocated their own routed IPv4 address through this setup.
You can also watch the Virgin Media ISP update video from Loba Olopade and it’s UK IPv6 plans.
The Virgin Media ISP update from 2018 can be found at the following timeline: 21:41–33:36.
Previous UK IPv6 Council presentations from Virgin Media can be found below:
2014:
- Slide deck — https://www.ipv6.org.uk/wp-content/uploads/2018/10/VM-IPv6-council-presentation.pdf
- Video — https://tv.theiet.org/?videoid=5899
According to the slide deck for 2014, Virgin Media had no plans to use CGNAT. Whoops. That plan, clearly changed . By this point Liberty Global had acquired Virgin Media and on one of the slides, Germany was referenced with IPv6 test with DS-Lite. So the use of DS-Lite looks to have been happening long before it was being tested in the UK.
2015:
Previous updates at the UK IPv6 council by Virgin Media were presented by Daryl Tanner who no longer seems to be part of the company since late 2016.
An interesting point to note during the latest Virgin Media update is that Liberty Global while preferring the DS-Lite approach, does have dual stack deployments in some countries. This could be for a variety of reasons such as inheriting a previous network setup through acquisition or merger and it being too costly to redesign or offering no financial benefits to change. So while it seems Virgin Media is potentially wedded to DS-Lite, it’s not an impossible scenario to think Virgin Media could change their plans.
Dual stack would be the preferred approach for the UK
BT and Sky both went with a dual stack deployment for their IPv6 rollout, to me this should be the approach Virgin Media should follow too. The fact Virgin Media seem to have chosen DS-Lite mainly due to cost and simplicity is a big call when two other major ISP providers in the UK decided against it and went the more intensive but purer path. You could argue that Sky was influenced by BT, given it’s ties to Openreach, but the point is two of the biggest broadband providers in the UK chose to dual stack and retained having a routed IPv4 alongside IPv6.
Dual stack provides IPv4 and IPv6 to a client with no funny business or minimal transitional technologies in the middle e.g. CGNAT. Yes, it means you are having to maintain two protocol networks, but ultimately isn’t the goal here to be long-term IPv6 only? Eventually, IPv4 will disappear one day and no one should (in theory) notice. CGNAT gateways for IPv4 will at some point not be needed. Why not invest in your IPv6 network now and future proof, otherwise aren’t businesses going to find themselves at this road again at some point when the transitional technology chosen previously is no longer fit for purpose because the world moved on?
One argument for Virgin Media to not dual stack could be the whole IPv4 exhaustion argument. What’s interesting is Virgin Media has often boasted that it has plenty of IPv4 address space available in the past and this has been cited to the reason why there has been no urgency to deploy IPv6.
For Virgin Media to then decide to choose a transitional method that basically removes native IPv4 entirely is a big reversal of events. You could argue that IPv4 address space is pretty valuable right now and at a high premium. Virgin Media could be planning to sell off some of their address space for additional revenue, but eventually it’s value will decrease as more and more ISPs and content providers deploy IPv6, so this seems like a short sighted approach and the longer they stay IPv4 only, the less you would profit from that. In the early days of the Liberty Global takeover, it is believed that some of Virgin Media’s IPv4 space was “raided” for use in other parts of Europe by Liberty Global.
Unfortunately, from what Virgin Media have been signalling with their IPv6 trial so far, they would be giving you the option between native IPv6 through DS-Lite and sacrificing your dynamic but routed IPv4, or stay IPv4 only forever on modem mode. Neither option being ideal for a long term sustainability and connectivity to the internet.
Have Virgin Media abandoned DS-Lite for the UK?
The fact that nothing happened throughout 2019 and there is still no firm date for when Virgin Media will roll out IPv6 has led to some to believe that Virgin Media may be abandoning their DS-Lite approach entirely. The update in 2018 from Virgin Media sounded like they had done the majority of the work to be IPv6 enabled/ready. Years later we are no closer to this happening it seems. An unknown piece of the puzzle I can only guess why prevents them from moving forward.
Their customer trials that were underway in mid 2018 have fallen flat, the IPv6 connection count from Virgin Media has gone very quiet. What exactly is happening inside their network with IPv6? What decisions are being made or considered? Will the UK break away from the typical Liberty Global DS-Lite deployment and follow the likes of BT and Sky?
Ultimately I hope that Virgin Media are reconsidering their approach. Perhaps the IPv6 trial flagged up that many users valued some of the more conventional IPv4 NAT configuration that is more common place like port forwarding for a variety of services. Don’t forget even the Super Hub allows you to do port forwarding without having to use your own kit.
If Virgin Media does eventually go ahead a roll out DS-Lite. I hope they offer a way to opt-out and to remain IPv4 only. It would be likely that anyone currently in modem mode now would likely be left alone, only customers using the Super Hub in router mode would probably get DS-Lite pushed at them. I’d potentially consider moving to their business side as I’d imagine they wouldn’t deploy DS-Lite for business users. They already offer static IPv4 options using a GRE tunnel (although the static IP configuration has reported to be a bit temperamental). They would likely provide something like a static /56 prefix to business customers if and when the business side supports IPv6.
For disclosure, I have had near native IPv6 connectivity for years thanks to Hurricane Electric and it’s tunnelbroker.net service. It works well, aside from performance issues with 6in4 specifically on Virgin Media, which has been documented and reported by many users in the past. So, while I could live with being IPv4 only with 6in4, it’s also not a sustainable IPv6 approach either, because 6in4 is also technically a transitional type of IPv6 deployment. The specific performance issues on Virgin Media residential lines aside, 6in4 itself has overhead per data packet so it isn’t the most performant method either.
Only time will tell if anything changes in 2020 and what Virgin Media UK will do regarding IPv6 (if anything!).
