WAN Acceleration takes Center Stage

Seamless connectivity across offices is becoming a necessity for every organization today, thanks to the growing number of applications. What's needed to achieve this are technologies that can optimize WAN connectivity. In this story, we explore these technologies and ways to implement them

Thursday, November 02, 2006

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We did a survey recently of IT managers and CIOs to find out the areas where they were planning to invest in the near future. Disaster recovery, workflow automation, server consolidation, and Voice over IP were some of the areas that received significant votes. The point to note about these areas is that they all require a proper and well-managed WAN infrastructure to be really effective.

You don't need a rocket scientist to tell you that you need high-speed and redundant WAN links for your disaster recovery site. All critical data must be backed up to the DR site on time so that you don't lose time and money shifting to it should (God forbid!) a disaster strike. In case of workflow automation, it isn't just about automating your company's internal business processes alone. In order for it to be fully effective, the entire eco-system of your company's suppliers, partners, customers, and even your own branch offices must be taken into account. This can only happen if you have well-managed WAN links. For instance, if you need to ensure that email gets priority over other traffic so that your important customer orders don't get delayed, you would need to put in place QoS policies for your WAN links. Moreover, if you want these orders to directly and immediately move into your manufacturing plant's ERP system, then you need to link it to the head office with dedicated leased links. You may want to use some WAN acceleration technology on it so that information moves faster and more efficiently. This is just one scenario, but as you can imagine, a proper WAN infrastructure is a must for most workflow scenarios.

Moving to server consolidation, today many organizations are toiling with the challenge of server proliferation. There are just too many of them in the house, be it a mail server, proxy server, web server, app server, database server, etc. Chances are that you might even have too many of them outside the house, i.e. across your various branches, at the ISP, customer location, etc. A proper server consolidation strategy is required in this case to centralize the infrastructure and reduce the number of servers. This saves cost and improves management. Unfortunately, with centralization, the burden of ensuring seamless connectivity between remote locations falls on the WAN links. The whole objective of consolidation fails if the WAN links go down.

Voice over IP is also growing in popularity, and many organizations are planning to bring it into their IT infrastructure. In order to really benefit from VoIP, you need to move all voice traffic from your branch offices to it. For this, you would need QoS policies, low latency, etc on the WAN links. If you also want to do audio and video conferencing on top of this, then you'll also need to add more bandwidth. There might also be a case where you want to centralize not only your servers, but your entire IT infrastructure. You only want thin clients at the remote locations so that there are no maintenance hassles there. Here again, you need to calculate how much bandwidth is needed and what sort of technologies to use on your WAN links for optimum performance.

So if you don't already have a proper and well managed WAN infrastructure, then you need to start acting now. This story is all about explaining the need for doing so, the WAN acceleration technologies that are available and their benefits, as well as some of the products and solutions that can be used for the job.

WAN Acceleration Tech
WAN acceleration technologies provide quick data availability between offices spread across distant geographical areas. Branch offices depend heavily on their head office to get regular data. Using WAN acceleration techniques can solve this. There are several WAN acceleration appliances available today that offer these features.

They accelerate the data transfer rate by utilizing a number of techniques like compression, data reduction, error correction, data caching, etc. Plus, they also utilize techniques to overcome drawbacks of protocols used over WAN. Of course not all such appliances would support all the acceleration techniques, so you'll have to first understand which are the techniques that are used, and then see the ones that would be suitable for your requirement. WAN acceleration appliances are deployed on both ends of the link where acceleration is required.

Compression: All incoming and outgoing data passes through them and appropriate acceleration techniques are applied. The most obvious acceleration technique is compression, wherein you use various compression algorithms to shrink the data. This will only work for data that is compressible, such as spreadsheets, Word documents, etc. This actually improves bandwidth utilization while transferring data. Files that are already compressed add to the benefit.

Some WAN Acceleration Products
Juniper Networks' WXC Application Acceleration Platform benefits IT staff involved in key business initiatives such as application rollout, data center consolidation and server centralization, disaster recovery and backup, and regulatory compliance.	SILVER PEAK NX-5500 is a 3RU appliance, equipped with 2 TB of local data stored in a RAID configuration. It supports up to 50 Mbps of WAN traffic, making it ideally suited for medium and large enterprise offices.

Redundancy reduction: The other major concept of acceleration is to reduce the data flow over the network. This is done by replacing redundant data packets by codes. Depending upon the technique used, whole packets or streams of packets could be scanned for redundant data. Another redundant element is the packet header, a serious overhead on WAN links. Multiple packets can be merged under the same header using a technique called packet coalescing. This can save a lot of bandwidth as packet headers can be upto 60 bytes long.

Caching: This concept is primarily used in proxy servers so that instead of going to the Internet to hunt for a website, the proxy caches it locally to save bandwidth. A similar thing can be done here as well. The WAN accelerators on either end inspect data being transmitted and store all duplicate data locally on their own cache. This way, every time the WAN accelerator at the other end asks for this data, only the code for it can be sent and the other WAN accelerator will simply deliver it locally. This will actually deliver LAN-speeds over WAN. This can significantly reduce traffic.

Error correction: There is one more reason that can make WAN links slow besides heavy traffic. This is retransmission due to errors. Bandwidth is actually being wasted if the appliance has to retransmit data everytime there's an error. So a technique called Forward Error Correction or FEC is used by these devices. This enables data correction at the physical layer by adding an additional data corrective packet.

VoIP: Polycom Communicator C100S
The Polycom Communicator is a high quality speaker phone that connects to a computer for use with Skype's VoIP service. The C100S comes with just a single USB cable that provides both connectivity with a computer as well as powering the device. This means there are no extra cables to carry around and neither do you need to recharge batteries. There are five buttons on the face of the device. Two of these are volume control buttons, one mute button, and one button that opens and closes the Skype connection. Another one is used to dial a call or accept an incoming call. This Communicator is very easy to install. First, you need to plug in the device to your desktop or notebook and then install either Polycom's software or Skype client in the system. After that, you can readily use the Skype client with the C100S as the handset device to call your associates and talk to them using your Skype ID. There are many pros to this product like its high frequency response, easy volume adjustment and excellent sound quality. The speakerphone will also show up in your Windows Control Panel as an option for audio input/output, letting you use it with other applications like listening to music as well. The communicator has a sleek and handy design with a rubber casing that can protect it. There are two cons to it-one, we feel the cost is on the higher side and two the C100S does not work with Linux or the Mac. This is a good buy for executives who make VoIP calls.
	Quick Specs Price: Rs 7,740 (1 yr warranty) Key Specs: Speaker phone, Skype client, powered through USB Contact: Polycom, Delhi Tel: 26207771 E-mail: pv.krishna@polycom.com

The process of adding an FEC packet is done dynamically, depending upon channel congestion. Normal protocols usually have the ability to correct at most one or two data packets if they're lost, but not beyond that. If more packets are lost, and have to be refetched, then the latency and traffic on the WAN links increases. FEC prevents data to be retransmitted as it will automatically generate the correct packet and give it locally.

Protocols over WAN
These include TCP (Transmission Control Protocol), CIFS (Common Internet File System), and NFS (Network File System). These protocols need to do a number of round trip requests and acknowledgements before sending the requested document or files. This can cause serious congestion on the WAN links.

Bandwidth Management with m0n0wall
If you are an ISP or a network admin, responsible for allocating bandwidth to a given set of users, bandwidth shaping would surely be one of the challenges for you. Here is a free and easy way to do so using a live CD called m0n0wall available as an ISO image from m0n0.ch/wall/downloads.php.  Setting up m0n0wall Burn the ISO onto a CD and then boot. The booting process is completely interaction-free as it does not ask the user to do anything. Once done, you will see a screen with six options. Select the second option and provide the IP address. Now go to another machine connected to the same network and open the m0n0wall GUI using its IP address in a browser. The default username and password are 'admin' and 'mono.' Shaping the traffic To create IP-based bandwidth pipes with different sizes, go to the 'Traffic Shaper' option under the Firewall tab. Now go to Pipe tab option and click on the '+' sign at the bottom of the table. This will open up a new page where you have to fill in the size and name of the pipe. After providing the details click on the Save button and the 'Apply Changes' button. Next we attach this pipe to an IP address. Go to the 'Rules' tab and click on the '+' button. The 'Target' drop down on the new page lists all the pipes that have been created. Select the pipe that you want to attach with the IP. For the 'Protocol' and 'Source Port Range' (both 'from' and 'to' options) fields, select 'any' from the drop down lists. And finally, in the 'Destination' field, first select the 'Single host or Alias' in the 'type' option and then fill in the IP address of the host in the address field below and also provide the subnet mask. Now any machine that uses this IP address will get only the bandwidth allocated to him in the respective pipe. Now click on the Save button and then on 'Apply Changes.' After the configuration has been saved, reboot the machine once.
	Set up inbound/outbound rules from the m0n0wall Web GUI's Traffic Shaper page to control how traffic flows between different systems

TCP acceleration requires packet resizing for optimal performance, which is done using TCP window adjustment algorithms. TCP acceleration also requires high speed TCP management and round trip management to provide correction for more than one packet loss. Similarly for CIFS and NFS caching techniques are used in which acceleration devices can generate read-ahead or write-behind requests to the server to reduce round trip delays.

Another technique used for faster file services over the WAN is WAFS (Wide Area File Services). This is more of a caching technique than a technology. If any file or request is made for first time, then that file is cached. If the same file is requested for again, then it's provided from cached memory.

While this technique can considerably improve performance over the WAN, it has some concerns as well. One is data protection. How secure is the data lying in the cache. Second issue is synchronization issues. What if the link goes down during a file transfer? Later the file it was supposed to send undergoes a change. Will the appliance send the new file, or will it pick up the old file from the cache and send it?

As the outsourcing wave takes a firm grip worldwide, thin client traffic is shaping up to become a significant portion of WAN traffic. So, we have included thin clients in this section.

The concept of thin clients is not new. All applications are hosted centrally on the server, and all that the remote thin client does is to pass the mouse, keyboard, and video signals over the WAN links. All processing is done at the server end. There are many benefits of this approach. Some of these are:

1. Savings in cost of deploying desktop PCs. Thin client devices don't have much hardware. In fact they don't even have a hard drive or RAM. They just have flash memory to store the configuration and the thin client software.
2. Users can access all applications running on different servers irrespective of platforms that they are hosted on, from one or many thin client devices.
3. They give better control over applications and data. With thin client deployments, you can manage software and applications centrally on the server.
4. Easy deployment.
5. The data is safe and protected as it resides on the central server instead of the client machine. Even the communication between thin clients and servers is encrypted.
6. Troubleshooting becomes easy for system administrators. In a network-centric infrastructure, all enterprise applications and software are delivered through the server. This simplifies administration of the infrastructure because your IT support staff can focus on a few servers instead of hundreds of individual desktop PCs. In addition, any new updates or changes to security software or applications on the server will get immediately reflected across all thin clients in the enterprise.

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