Facebook's pending IPO is getting all the headlines, but there are a number of IT companies -- many with robust channel programs -- that have been mentioned as potential IPO candidates, and many of those are in the networking and infrastructure spaces.

Some have made their IPO intentions quite clear, others have been a little bit more cagey but have taken in large sums of venture capital funding and entered late-stage startup status, and still others are getting mentioned with greater frequency following a run of other high-profile M&A moves and IPO declarations.

Following are 10 companies, listed in alphabetical order, that are heavy with IPO buzz -- and are also much-discussed acquisition targets.

The buzz on Aerohive has gotten consistently louder as the company racks up channel and customer accolades for its "cooperative control" wireless LAN architecture and continues to receive VC funding, including a $25 million Series D round of financing about a year ago. Aerohive has also continued to expand its focus beyond basic wireless LAN needs, including branch offices, Apple-related BYOD hassles and cloud networking.

You don't need to go far to understand Arista's plans: the company describes itself on its corporate Web page as a "pre-IPO company igniting low latency data centers, cloud networking and computing environments." Data center specialist Arista is unique among many hot pre-IPO companies because it has taken in no venture capital funding, and is instead financed by its principals. Arista CEO Jayshree Ullal told Reuters earlier in March that the company is not only profitable but is also investing lot of its profits into R&D, sales and marketing -- and has been fending off potential acquirers during its march to IPO. Ullal told Reuters that Arista is looking to expand its board of directors in the second half of 2012 or early in 2013, about its intended timeframe for an IPO.

Eight-year-old A10 came off 2011 with some of its strongest-ever industry notices, including the growing admiration of application delivery-focused channel partners, and the rank of No. 54 on Inc. 500's annual ranking of the country's fastest growing private companies, reporting about $55.1 million in revenue for 2010.

The ADC market is a crowded space -- F5, which crossed the $1 billion revenue mark this year, is the king of the mountain -- but it's also an expanding market, and one expected to be that much more relevant for cloud- and data center-focused VARs this year than ever before. A10 CEO Lee Chen told ITPro UK last summer that he would not sell the company, and that an IPO is in the pipeline, possibly within two years.

The darling of the next-generation firewall space, Palo Alto Networks has been cash-flow positive for eight quarters now. New CEO Mark McLaughlin told CRN last fall at Palo Alto's Double Down Partner Conference that the company was hiring between 100 and 125 new employees every quarter.

"It is a possibility for the company," McLaughlin said when asked about Palo Alto's long-rumored IPO plans. "We don't need to raise any capital. We've been cash-flow-positive for some time, so we have a great deal of flexibility on that. It's one way to raise additional capital."

"The company today could be public based on its financials," he added.

The IPO stars seem to be aligning for hosted VoIP player RingCentral, which grabbed $10 million in Series D funding last year from Cisco and Scale Venture Partners, and hired a chief financial officer, Robert Lawson, a veteran of Intuit, General Electric and most recently, Codexis, which went public in 2010.

Founded in 2003, RingCentral has more than 200,000 customers worldwide and focuses on the SMB segment. It launched a formal reseller program in September 2010 and partners with IT consultants, MSPs and VARs.

There's no hotter startup in the wireless LAN space than Ruckus Wireless, which is beloved by channel partners and hoping to follow in the footsteps of successful IPOs by its main enterprise WLAN competitors Aruba Networks and Meru Networks. Ruckus has gained market share in both enterprise WLAN and carrier-grade Wi-Fi, has been at the center of some major national wireless deployments, and copped a $21.7 million financing round in February, making its total venture pull about $72.7 million since its founding in 2004.

Siemens Enterprise Communications CEO Hamid Akhavan made no bones about it in a recent Reuters interview: the company wants an IPO in the United States by the end of 2012. Siemens, which is a joint venture of Siemens AG and private equity The Gores Group, went through a painful restructuring over the past several years but has built up its North America channel strategy and emerged as a buzzed-about competitor to unified communications titans like Cisco, Avaya and Microsoft.

"Everyone had questioned our viability," said Chris Hummel, president for North America of Siemens Enterprise Commiunications and its global chief marketing officer, in a recent interview with CRN. "We were a $6 billion business and now we're a $3 billion business. Those are the facts. In the U.S. we needed confidence, and now our aspirations can get bigger and we can set our goals a little higher."

Founded in 2004, Silver Peak is a dark horse in the crowded WAN optimization space dominated by bigger competitors like Riverbed, Cisco and Blue Coat. Silver Peak, however, has an ace up its sleeve -- a well-regarded channel program that began in the storage channel -- and a technology portfolio so admired that Silver Peak was moved into the prestigious "Leaders" quadrant in researcher Gartner's most recent Magic Quadrant for WAN Optimization Controllers.

Among the software-centric startups eating into the crowded videoconferencing space, Vidyo is perhaps the best-known and definitely one of the best-funded. Vidyo in September 2011 said it had closed a $22.5 million Series D financing round, and has been steady in its product updates, including VidyoPanorama, a multi-screen telepresence system to enable up to nine screens delivering 1080p at 60fps video. Vidyo has attracted a number of veteran video, networking and infrastructure executives, and has a multi-pronged channel strategy encompassing VARs, service providers and development partners.

Open-source networking specialist Vyatta is one of the most closely watched startups in the industry, having cultivated a presence among solution providers and seeing its revenue nearly triple from 2010 to 2011. Vyatta in November copped $12 million in venture capital funding -- bringing its total VC purse to more than $45 million. Its advantage over other startups its size is that it has a channel following in place already, having cultivated well-known partners like Torrey Point interested in data center optimization, virtualization and networking services to support cloud computing.

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