Why Netflix is at a new all-time high

Netflix's embrace of original content isn't the only reason why its share prices are at an all-time high.

Groundbreaking news that Virgin Media is bringing Netflix directly to its set-top box in the U.K. in effect elevates Netflix to the status of a new cable network—a benefit for a cable company and beyond being an upstart threat to cable.

The deal, which makes Netflix available on cable set-top boxes for the first time, was announced Monday. On Tuesday, Netflix shares hit a new all-time high, trading 6.5 percent higher to $313, flying past its record $304 on July 13, 2011. (Click here for Netflix's latest stock price.)

The stock's nearly 220 percent gains this year have been driven largely by the success of its original content deals, which have helped add new subscribers, giving Wall Street confidence that exclusive originals will continue to deliver.

Virgin's parent, Liberty Global, gained just under a percentage point on Tuesday's news.

Virgin Media's partnership with Netflix is the first time a cable operator is bringing the streaming service directly to the set-top box. Other cable operators—like Comcast—allow users to access Netflix through Internet-connected set-top boxes—but this is the first time a cable channel has directly made a deal with Netflix to treat its content just like that provided by cable channels like HBO (owned by Time Warner) and Showtime (owned by CBS). (Disclosure: Comcast is the owner of NBCUniversal, the parent company of CNBC and CNBC.com.)

Virgin will integrate Netflix with its television content so it's easy to seamlessly browse and search across both TV and streaming content.

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So, for example, searching for Kevin Spacey content on Virgin Media's pay TV system will yield Netflix's exclusive "House of Cards" as well as movies he has starred in.

Virgin will start with a pilot of 40,000 households, rolling out to 1.7 million Virgin Media TiVo homes by the end of the year. This isn't free for those customers—Virgin's subscribers will still have to pay a standard Netflix subscription. But the idea is that Netflix will help make Virgin more compelling than its much larger rival, Sky, which has over 10 million subscribers to its satellite TV service. We'll see whether Virgin ends up rolling out Netflix to the 2 million-plus other subscribers it has but don't have TiVo boxes. (The fact that Virgin is trying this first with TiVo boxes makes perfect sense—since TiVo already integrates Netflix into its regular boxes.)

Looking even more broadly, we'll see whether the Virgin partnership is successful enough to prompt parent Liberty Global to copy the partnership for all of its 25 million global customers. Even if Liberty only extends the partnership to some of its global pay TV carriers, that would do wonders for Netflix's global footprint.

Doug Anmuth, JPMorgan's analyst covering Netflix, said that the Virgin partnership should help strengthen Netflix's U.K. market position, making it easier to sign up for Netflix since additional hardware, like an Apple TV or Roku box, would no longer be required.

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Netflix said it doesn't have any plans to roll out anything similar with U.S. cable carriers, but this shift of a cable company treating Netflix as an ally rather than a rival in the fight for subscribers is a promising one for its future.

The loser of this situation? The channels viewers won't be watching while they're streaming Netflix. Janney analyst Tony Wible called this news "incrementally negative for traditional networks."

Now that Netflix content is only a click away, he said, "we expect to see higher utilization of the Netflix service, which we believe will come at the expense [at least in part] of traditional TV networks, particularly for lesser-watched programming."

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—By CNBC's Julia Boorstin. Follow her on Twitter: @JBoorstin