WAN acceleration on the ocean wave

Two luxury cruise lines faced the same satellite-delay challenges for shipboard Internet access and came up with different ways to address the unavoidable latency on those ship-to-shore connections and keep passengers happy.

In one case, Regent Seven Seas opted for deploying Riverbed Steelhead WAN accelerators on each ship, and another at the satellite downlink in New Jersey, to attain higher throughput over the 256kbit/s burstable satellite circuit.

In the other, Crystal Cruises installed a single F5 Big-IP device at the satellite down station in California, which provides a 512kbit/s connection to Crystal ships.

Both lines say the WAN gear has boosted performance significantly enough to cut the need for buying more bandwidth from the satellite provider, MTN Global Networks, a division of SeaMobile.

In the case of Regent Seven Seas, the 256kbit/s bandwidth can spike to 512kbit/s when needed. All passenger and crew have Internet access, email, mobile phone service, and data to and from the ship goes over the satellite. Because of the vast distances involved between the satellites, ships and ground stations and the speed limit on the radio frequencies, the connections experience latency of more than 600 milliseconds.

Rather than use Riverbed gear directly on passenger traffic, Regent Seven Seas uses it to reduce the amount of bandwidth it takes to transmit administrative traffic. Through an arrangement with its satellite provider, passenger Internet bandwidth management is outsourced and already includes WAN optimisation techniques, says Vincent Cirel, CIO of Regent Seven Seas.

By optimising the administrative traffic with Riverbed gear, more of the satellite bandwidth remains available to passengers for Internet access, he says.

"The property management systems, the financial systems, just the overall maintenance activity that has to take place for remoting into servers onboard the ship - there are very, very high bandwidth requirements particularly for doing file transfers," Cirel says. "Without the deployment of the Riverbed devices on the admin side of the network we would be crowding out the passenger usage requirements, and it would mean we'd have to monitor things a lot more closely than we do."

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For instance, if a ship were at sea with no landing scheduled that day, up to 300 passengers might be logged on to the Internet at the same time. "We would have to look at the itinerary and decide if we prioritise the admin traffic, what is that going to do to the passenger traffic?" he says.

With Riverbed optimisation, that kind of time-consuming decision comes up less often. "By deploying this type of technology, we remove a lot of that manual analysis," he says.

Tests by the cruise line find that a 20.3MB file takes 18 minutes, 59 seconds to copy over the satellite link alone. With the Riverbed gear turned on that drops to 4 minutes 50 seconds. Similar tests for an 18.4MB file drops the transfer time from 17 minutes, 20 seconds, to 3 minutes, 50 seconds. Caching bit patterns at either end of the link was not applied during these tests, but would reduce times further, the cruise line says.

Meanwhile, Crystal Cruises opted for F5 gear that sits on the land end of ship-to-Internet connections because the company is reluctant to put more gear on ships than is absolutely necessary. "If I can in any way avoid putting equipment out there that has the possibility of breaking, I'll do it," says Bjorn Andersson, manager of shipboard and network operations for Crystal Cruises.

"Everything you buy for a ship, you have to buy two of. We go down to Antarctica and we're seven days away from being in the civilised world. If a box breaks and we don't have a backup appliance out there, it could take a week or two weeks to get it fixed."

Crystal applies the device to all traffic from its ships. Crystal didn't have comparisons of the time it takes for transfers with and without acceleration, but did say F5's gear met a purchase agreement that guaranteed the device would improve the load time for Web pages by 50 per cent. The device exceeded the promised performance, Andersson says.

That improvement has resulted in a jump in Internet use, he says. Before the accelerator was installed, the satellite link was so slow that ship traffic never filled it. With the improved performance, the ships routinely burst above the 512kbit/s contracted for.

"We went from spiking 30 minutes per day to spiking between 14 and 17 hours per day - pretty much the hours when anybody was awake," Andersson says. The highest spikes reach 4Mbit/s per ship.

The company hasn't tried a two-ended acceleration product, but it may check one out if increasing Internet traffic chokes the current accelerator.

"I'm sure we can gain additional performance by doing something along those lines," Andersson says, "but just the significant improvement we've gotten so far and how it helped us utilise the satellite, we don't have the need now for a two-ended device."