An increasing percentage of WAN traffic is now SSL-encrypted, which is posing problems for WAN optimisation systems, according to a survey of over 1,300 IT professionals.

According to the survey, sponsored by Blue Coat Systems, 53 percent of enterprises have SSL-enabled applications now, 45 percent plan to use them over the next year, and for 35 percent, SSL already represents at least a quarter of their WAN traffic. Almost two-thirds of those surveyed said that their SSL-encrypted traffic would increase during 2007.

Many web-enabled enterprise apps now use SSL for security, for example Microsoft Sharepoint, as do outsourced software services such as, according to Chris King, Blue Coat's strategic marketing director. However, a WAN acceleration appliance cannot monitor, control and accelerate traffic flows that it cannot see inside.

"Today, if it's important, it's encrypted - and it can be traffic from outsourced or internally-hosted applications," King said. "Any enterprise-grade WAN optimisation solution must manage and accelerate SSL-encrypted traffic along with other vital traffic."

A few WAN optimisation companies have already added SSL acceleration, such as Blue Coat, F5 Networks and Riverbed. Others understood to be working on it include Expand Networks, Juniper and Silver Peak.

Riverbed announced an SSL-capable software update for its Steelhead boxes this week. It said its own customers report that 15 percent of enterprise WAN traffic is SSL-encrypted, and that this is growing by 52 percent a year.

However, while Riverbed can accelerate SSL within the enterprise, Blue Coat claimed that its SG devices are the only ones that can also accelerate SSL-encrypted traffic from external sources.