Poorly performing WAN links continue to be the bane of many network administrators. Wherever there is a WAN link, there will be performance degradation caused by latency and chatty protocols. Simply adding bandwidth is not the answer. Using appliance-based solutions on each end of the WAN circuit, however, can improve overall response time and throughput.

Packeteer's iShared solution, part of the Tacit acquisition completed in May, uses multiple layers of technology to reduce response time and improve WAN performance. Based on Windows Storage Server 2003 R2, this 2U appliance uses both file- and block-level caching to help decrease traffic on the WAN and provide native DFS (distributed file system) namespace integration. Protocol support includes CIFS, NFS, HTTP, and Microsoft Exchange, and a TCP acceleration service handles other protocol chores (sorry, no support for UDP). Admins can schedule push/pull operations to pre-populate data at the branch office location and define optimization rules for specific applications.

I tested the iShared IS 100 (datacenter) and IS 100 BR (branch office) appliances with the same test tools used for previous WAN optimization and acceleration reviews and found the solution to provide a good overall performance increase. When dealing with CIFS traffic, iShared was hands down the best performing appliance I've tested, beating

Cisco's and Riverbed rival solutions under all test conditions. iShared faltered, however, when dealing with FTP traffic. Although still up to nearly eight times better than without optimization, FTP performance greatly lagged behind that of other appliances. iShared's Exchange/MAPI solution is cumbersome both on setup and deployment and didn't net the same performance increases as other solutions.

Different from its peers

The iShared is unique among all of the WAN optimization appliances I've reviewed in the past couple of years. Whereas the rivals run on some Unix/Linux variant, iShared runs on Windows Storage Server R2. This approach was quite deliberate, allowing iShared to hook into an existing DFS deployment natively, letting it cache DFS metadata on the branch office appliances.

Being a native Windows product allows Packeteer to dig deep into the CIFS architecture to post the excellent performance gains. Using its CIFS application proxy, iShared is able to reduce significantly the amount of protocol chatter across the WAN while maintaining end-to-end file locking. Much like other WAN appliances, iShared stores blocks of data on local disks. When files are requested across the WAN, blocks that match previously transferred data are served from the local disk cache and not transmitted across the link. In my testing, this service proved efficient when working with CIFS traffic, whether during a simple file copy or repeated file-open-close scenario.

iShared's capability to optimize SMB (Server Message Block)-signed traffic is an important feature. SMB signing places a digital signature into each SMB to secure network communications between Windows clients and servers. It is turned on by default on Windows 2003 domain controllers. Many WAN accelerators, such as those from Riverbed and Cisco, cannot optimize SMB-signed traffic. Rather, the traffic passes sans optimization, or network admins must disable the feature on their servers. Given that most file shares do not reside on the domain controller, this feature may not be of much use in many networks. But it has been rumored that SMB signing will be enabled in Microsoft's next-gen server Longhorn in all situations, making this feature more important in the future.

iShared's deep collaboration with Windows proves to cut both ways. It requires additional steps to integrate the appliance with the file servers and other resources on the network. It isn't nearly as transparent to the resources it is optimizing and requires pretty detailed knowledge of the network in order to bring it online. Setup time was close to double the time required for other appliances.