AT&T today joined the SD-WAN party, in the process giving another boost to startup VeloCloud, as its initial partner in the effort.

Other major players, including BT, Verizon and CenturyLink, have launched SD-WAN services beginning a year ago, as have many smaller companies and managed service providers. The service is finding appeal among businesses who need flexible connections in a wider range of places for cloud access and mobility, but don't want to pay to set up MPLS links to every remote office or site. SD-WANs enable them to use Internet access for those connections. (See AT&T Launches SD-WAN With VeloCloud and Will SD-WANs Buck Past Trends?)

AT&T Inc. (NYSE: T) is saying its service will be differentiated in this increasingly crowded market by its integration into the company's AT&T FlexWare devices, which today deliver other virtual network functions, and by connections into AT&T Integrated Cloud nodes.

AT&T also is touting the ability to provide SD-WANs over multiple network access types, providing additional flexibility and promising to be the single throat to choke when something goes wrong. The service will have the ability to select the best access network for a given application at a given time, according to AT&T.

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The carrier says a premises-based solution will be available later this year for customers who want to add SD-WAN to an existing site, while the network-based SD-WAN capabilities will be available later this year.

VeloCloud Networks Inc. , which earlier this year closed its second funding round from companies including Cisco, has emerged as a leader in this space, with more than 100 customers including NTT Data Corp., Deutsche Telekom and, more recently, EarthLink. VeloCloud software runs on x86-based hardware in branch offices -- in AT&T's case, these are apparently the FlexWare devices it uses to deliver other VNFs -- and connects to gateway servers that VeloCloud runs on public and private cloud infrastructure. (See Cisco Joins $27M Round for SD-WAN Startup VeloCloud.)

AT&T says it will also be cooperating with other SD-WAN technology vendors going forward, in addition to VeloCloud.

— Carol Wilson, Editor-at-Large, Light Reading