It's not an easy time for networking start-ups to secure venture capital funds, but a trio of WAN optimization players managed to boost their respective corporate coffers in recent weeks.

Even though it has been eight years since the dot-com bubble burst, investors are still taking a hit from the excesses of 1999 and 2000, according to Tracy Lefteroff, global managing partner of PricewaterhouseCoopers. Lefteroff spoke with my colleague Jon Brodkin about how those network sector losses are making it harder for newcomers in the network arena to secure funding.

But despite the difficult climate, Silver Peak Systems, Anagran and NetStreams (three companies with very different technologies for optimizing network traffic) each closed new rounds of venture funding. Here are some details:

* Silver Peak Systems secured $21 million in series D funding, bringing the total investment in the company to $63 million. Silver Peak specializes in optimization gear designed for the largest WAN links -- DS3 and OC3 data center replication and backup environments, for example. Its latest round of funding includes investments from Artis Capital Management, Benchmark Capital, Duff Ackerman and Goodrich, Greylock Partners, J. & W. Seligman & Co, and Pinnacle Ventures. The WAN acceleration vendor says it will use the funds to expand all areas of its business, including engineering, sales, marketing and support.

* Start-up Anagran came away with $12 million in its Series C round of funding. Anagran’s flagship product is the FR-1000 device, which is designed to work in conjunction with routers and other existing network equipment to improve the performance of IP-based video, voice, data and wireless traffic. Anagran’s technology looks at flows traveling through the network (it describes a “flow” as an end-to-end activity over the network, such as a video download, voice call or image transfer) rather than concentrating on a succession of individual packets. Anagran was founded by Larry Roberts, one of the developers of ARPANET, a precursor to the Internet of today. The company says the new monies will be used to expand its sales presence in North America and EMEA.

* NetStreams wrapped up $18.2 million in its series B round of funding, which it plans to use to continue development and sales of its IP audio and video distribution systems. Headquartered in Austin, Tex., NetStreams makes networked entertainment systems based on IP technology; its DigiLinX system lets users distribute uncompressed, high definition audio and video to multiple rooms throughout a commercial facility (or home) over a TCP/IP network, for example. Its StreamNet technology provides features including A/V signal synchronization, automatic device discovery and configuration, remote access control, and software upgrades. Austin Ventures led NetStreams’ latest funding round.

Ann Bednarz is associate news editor at Network World.