WAN Performance

Tips For Optimizing Your WAN (Wide Area Network)

2010-03-15T18:18:00.000-07:00

So you're looking to optimize your WAN for your business and need to know what your options are. Upgrading your bandwidth to MPLS or Ethernet isn't necessarily the solution. Bandwidth utilization is the key for optimizing your WAN.

Packeteer, Riverbed and Juniper are WAN optimization systems that do an excellent job with latency, especially if CIFS WAN-unaware situations such as opening, copying and modifying files using Windows are the main problem.

To identify the delay, you need to find the path your IP packets take. A satellite connection versus a landline connection (such as earthbound wireless, land or underwater fibre) can be the source of the latency problem. Check with your service provider to get a service level agreement to guarantee the quality parameters you want concerning packet loss, delay and jitter.

It's very important to not buy or install any new network system before identifying existing delays.

Once the latency issue is identified, a valid solution for optimizing your WAN is to purchase a WAN-accelerator from a vendor that offers such a product. The amount of traffic your WAN uses will also determine which vendor you will choose for this product. For example, if your business uses such programs as Citrix and SAP, then a traffic-prioritizing WAN accelerator such as Packeteer or Ipanema would be the best solution. But if your business uses more file-oriented applications, your best option would be to purchase a data reduction accelerator like Riverbed, Juniper Citrix and Cisco. Riverbed is by far the best solution.

While optimization systems effect only TCP flows, latency issues with UDP flows (VoIP) can't be resolved since real-time traffic is naturally subject to delays. Citrix WANScaler, Cisco WAAS, Juniper, Riverbed and Expand as well as other vendors sell systems for optimizing generic TCP flows which would meet the needs of your business.

As a word of caution, all the vendors hide the effects of latency. WAN optimization solutions act like an invisible TCP proxy, simultaneously spoofing both the server's IP address to the client and the client's IP address to the server. The TCP ACK messages are sent locally, speeding up the delivery of the ACK message and avoiding latency effects. TCP connections and throughput are subject to latency when the ACK messages are returned.

Vendors also hide the effects of latency by utilizing the entire WAN bandwidth link for implementing selective ACKs and large initial flow control windows. Compression mechanisms, layer 7 optimizations (mostly CIFS file-sharing as well as HTTP-based compression), embedded QoS are used for artificially increasing bandwidth not in use. This is known as "WAN optimization".
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Reducing Costs - WAN Acceleration

2010-03-01T18:16:00.000-08:00

According to Gartner, WAN optimization is about improving the performance of business applications over WAN connections. Most networks carry a variety of types of traffic, of differing characteristics and importance.

Many organizations are striving to manage this traffic to optimize the response times of critical applications and reduce costs, given that bandwidth continues to represent a significant proportion of operating expenditure for wide-area data networks.

The primary function of a Web Optimization Controller (WOC) is to improve the response times of business-critical applications over WAN links, but they can also help to maximize return on the investment in WAN bandwidth, and sometimes avoid the need for costly bandwidth upgrades. To achieve these objectives, WOCs use a combination of techniques, including:

- Ensuring fair access for mission-critical applications during periods of congestion by prioritizing business critical traffic, through QoS policing and traffic shaping, for example

- Minimizing the effects of network latency using methods like protocol- and application-specific optimization

- Reducing the bandwidth required to transfer WAN traffic by compressing it, for example.

Click here to read more from Gartner about the WAN optimization market.

The WOC market is maturing rapidly, but it is still dynamic with a high level of vendor innovation.This has led to different vendors offering different combinations of features. In order to ensure that the most effective solution is put in place, providing the best overall return on investment, a detailed analysis should first be undertaken. This will establish:

- The real bandwidth you are achieving

- The real usage of that bandwidth

- Applications and services running on your network and the protocols they use

Also conduct a detailed analysis of your network traffic to identify specific problems, for example, excessive latency, bandwidth over subscription or lack of prioritization for certain types of traffic.

The Importance of Keeping Up With WAN Optimization Techniques

2010-02-17T18:15:00.000-08:00

To understand the different techniques used by appliances offering WAN optimization, it's important to first define exactly what exactly a 'WAN' is. WAN stands for 'wide area network' and refers to any network that covers a very large geographic area. By contrast, a LAN, or local area network, refers to networks that provide internal communication in a home or small office. The internet as a whole can be defined as a WAN and is obviously a public network, while an example of a private WAN could be a corporation with offices in San Francisco, San Jose, Austin, Boston, and New York. Each individual office would have a LAN set up internally, but could also use DSL or MPLS connections to form a WAN to share information between offices.

There are a number of performance-related issues that typically occur with WANs, which has led to the development of various WAN optimization techniques. These issues can include redundant transmissions, 'chatty' protocols, and packet delivery issues. Some of the common techniques used to achieve WAN optimization include: Bandwidth Management; Caching; and Protocol Optimization. Multiple vendors offer WAN optimization appliances that use a number of these techniques to process the IP traffic traveling between the sites over the company's WAN. Not every solution uses the same techniques, thus the benefits can vary, which is important to understand when researching a vendor or supplier.

Bandwidth Management allows applications to have set limits and minimums with regard to how much bandwidth they use. For example, this technique would allow you to put a limit on the amount of bandwidth an especially avaricious application can use. Conversely, bandwidth management can ensure that less-used applications always have a guaranteed amount of bandwidth allocated to them.

Caching allows several copies of important files, especially larger ones, to be stored in multiple locations. This prevents users from having to download files as large as 20MB or 100MB across a WAN connection every time they need to view or make edits to it. Additionally, whenever modifications are made to one of these cached files, the network doesn't have to transmit the entire updated file to every one of its multiple locations. One the portions of the file that have been edited are sent.

Communication protocols for digital computer network communication have features intended to ensure reliable interchange of data over an imperfect communication channel. It is basically a way of following certain rules so that a system works properly. Protocol optimization restricts the amount of electronic chit-chat that occurs between sites when communication protocols send their necessary back and forth confirmation messages.

The implementation of these various techniques by using WAN optimization appliances has been said to reduce the usage of bandwidth by as much as 50-95% between offices communicating over the WAN. For many companies this means thousands of dollars of savings, particularly when costly solutions like multiple MPLS networks are being to ensure network reliability. For others, the value of WAN optimization is that global collaboration allows the company to undertake tasks that it previously couldn't. Regardless of the benefit or the need, understanding the latest in WAN Optimization techniques can have a substantial benefit on the performance of a modern corporation.

Charles Hughes is author of this article on WAN Optimization.

When Should You Add More Bandwidth To Your Business Network (eg WAN)?

2010-02-01T18:13:00.000-08:00

Many businesses ask this question. It's common ..... so don't feel alone.

Is there a general rule of thumb, a percentage of bandwidth usage, that is an indicator that it is time to lease more bandwidth?

The true answer here is, "It depends".

Of course you need to know how many users you have ..... and what they're using the network for (e.g. CAD, Multi-media applications, sharing large data files, medical imagery, etc.). That's a factor in your ultimate decision obviously. As is what is the operation, are users on one side and servers on the other, are servers and users on both sides, how many points? Plus .... are either of those categories (number of users, applications) going to grow in the near future.

If growth of users and/or applications is in the distant future ..... you have more room to plan and maybe go with a gradual solution in the interim. In this case you may be able to go with a bonded T1 or burstable DS3 bandwidth rather than a full DS3 or OC3 bandwidth.

Before you can make a real decision on increasing your bandwidth though (thus increasing your expenses) the first step is to log/record your bandwidth usage patterns for a specific period of time - I'd say at least a month (30 day period). This will create a decent benchmark on where you stand in regards to your bandwidth needs.

Ignore occasional spikes -- spikes will happen, this is a reality of networking. However if you have sustained spikes lasting for several minutes at a time and this occurs at least once every day that is a hint of a larger problem.

(If that happened I'd note the time of day such spiking occurs, then correlate the times if they match up to any specific task the company is doing during that time period each day).

However, as a general rule ..... look at the bandwidth usage throughout the day. If the average usage is at 50% then start to talk about increasing the bandwidth. If it's at 70%, you will start seeing major trouble, don't just talk about increasing bandwidth then, DO IT.

If you want to be a bit more lenient rather than conservative on your benchmarks ..... get excited about increasing bandwidth when you consistently see usage at 75% bandwidth, when it hits 85% there is no debate, no talking ..... just order more bandwidth.

But, remember to base your decision on the average usage ..... not the spikes that may occur during the day. Again, spikes will happen no matter what your bandwidth is.

Here's another tip (or two) .......

Much of the time bandwidth is not the problem, but the amount of clutter and the lack of optimization at the machine level.

So ..... on every computer on the network do the following:

First, delete any temporary files (even temporary system files) in the c:\windows\temp directory and in their profile under local settings.

Second, get rid of any unused applications.

Third, ensure that the swap file is optimized.

Fourth, Stick more memory in the system if possible.

Last, Defrag the hard drive!

Following the above you should be able to reclaim some speed. If speed is your main issue (it isn't always).

Also .... if you get your files of a network server don't forget to optimize that as well. But the first rule we tell users is do not work off server copies if you can help it.

Now, if after going through all of the above you still decide you do need more bandwidth ..... you can get free assistance to find the right solution (at the best price too) at DS3-Bandwidth.com.

Michael is the owner of FreedomFire Communications....including DS3-Bandwidth.com and Business-VoIP-Solution.com. Michael also authors Broadband Nation where you're always welcome to drop in and catch up on the latest BroadBand news, tips, insights, and ramblings for the masses.

LAN & WAN - Does a Letter Really Change the Meaning of the Word?

2010-01-15T18:12:00.000-08:00

Of course! Particularly when that one letter is a part of an acronym. As with the topic at hand, the difference between LAN and WAN lies deeper than the obvious spelling and phonetic. In many respects, there exist no single distinction between local area network (LAN) and wide area network (WAN). But there are, in reality, several differences that may well distinguish LAN from WAN.

The points to be considered are the following: geographic, connections, topology, usage, reliability and of course, the cost. We will first touch the comparison with regard to the geographic scope.

Scope

Given what LAN and WAN stand for, one can easily identify an immediate difference: the scope of WAN is clearly vast as compared to that of LAN. The former possesses networks that could spread across city to city, sometimes even on a broader scope. With that said, LAN may be deemed as an undersized version of a WAN and is usually limited to a single edifice or a residential house. So if you connect all the LANs then you may have just developed a WAN---a small scale WAN, that is.

Connections

On a local area network, Ethernet is the established standard for connecting computers or workstations. In here, wires and cables are but permanent. This arrangement allows interconnectivity among separate local area networks. As for the wide area networks, they almost always depend on common carriers or a system where they utilize or hire service providers to be able to interconnect.

With the issue on speed, LAN is approximately ten times faster than WAN. One cannot impartially compare the LAN's speed reaching 10 gigabits per second to a WAN's fastest speed of 155 megabits per second. (Talk about no competition.)

Network Topology

As shown in the previous paragraphs, WANs and LANs are configured differently. More often than not, the latter is inclined to be a peer-to-peer networking where one computer may share (and sometimes access) data and applications in other computer units within the network. While WAN operates in a client-to-server level and most, if not all, data originates from a central computer or server.

Usage

Continuing the discussion, the peer-to-peer sharing is commonly used to access files, as well as printers, scanners and other peripherals. The usage is somewhat controlled and restricted among a few groups of people. These users have their own passwords that will allow them to access a particular data (not the entire folder or drive). An administrator may also be present. In a WAN, it is not really the sharing of peripherals or whatnot, it stresses more on communications.

Reliability

LAN boasts a higher reliability rate because when one computer fails, all other will continue to operate. In WAN, this is not the scenario. When a unit falters in a WAN, most probably the rest will fail to function as well.

Cost

With the extent of WAN's reach, obviously this costs a lot. Not to mention the need for field experts like engineers to install and maintain all their machines. Sometimes, WAN also necessitates satellite links; yet another reason for its high set-up cost. Local area network, though housed in a single building, will prove to be more cost efficient.

So, in simple equation, WAN=vast reach=costly while LAN=limited extent=cost efficient.

Finally, to answer question posted above (yet again), there is a yawning gap between the WAN and the LAN.

Benedict Yossarian is specialises in internet marketing. Benedict recommends Comm store for networking hardware and Cat5 Cable. For IT training Benedict recommends New Horizons Learning Centres

How Do You Determine the Right Wide Area Network (WAN) Architecture For a Computer Network?

2010-01-01T18:03:00.000-08:00

One of the most complicated decisions to make for an IT department concerns the architecture for a multi-site voice/data network. Should the network be based on simple T1 point-to-point bandwidth circuits? How about burstable DS3 bandwidth or maybe a single OC3 bandwidth cloud? No matter the bandwidth chosen .... the most efficient design should base the communication backbone on a MPLS configuration (Multi-Protocol Label Switching).

To get there, first and foremost in deciding about the WAN architecture of any organization communication network you must determine ....

- How many locations you would like to connect?

- Architecture - hub and spoke or mesh architecture?

- What applications would be run on this network .... Voice, Video, Data, all of the above?

- Precisely which applications will be run in case of Data?

- What will be the % each will take up of your QoS, the total of all three should be 100%?

- Voice is the premium level QoS and hence the most expensive as it is a real time communication, followed by video and then data.

- How many users precisely will be using the network at a given point of time at each location?

- What will be the concurrency factor? Are you are looking for 100% concurrency or you can manage with lesser concurrency?

- What is the scope of scalability at each location and hub location?

- Will the access to internet also be given to users?

- Internet at a central location can help you in implementing and enforcing various security policies of your organization.

- Do you want to give access to the network resources to a mobile user?

The answer to all these questions will help in arriving at the MPLS bandwidth required at each hub and spoke location.

Honestly speaking no organization should ideally try to do this calculation themselves. Instead they can hire a consultant or a telecom service provider to do this activity as they are experts in designing this solution. With their help you can easily decide upon the bandwidth for each location, select suitable router, make redundancy plans, routing the traffic on Atlantic or pacific routes, blah blah.

For help walking through the analysis .... and determining the best solution .... take advantage of the free help at DS3-Bandwidth.com.

Ideally I also recommend to give the freedom of providing and managing the routers at each location to the Telecom service provider. Then it becomes a managed solution and the service provider can easily monitor your network in the event of an outage. They then can remotely login into the routers and manage your complete network giving you higher uptimes and SLAs.

In the end .... take a deep breath and work through the steps above, also helps to increase SharePoint Performance. Following this simple game plan will get you to the right decision for your organizations network architecture.

What You Should Consider For a WAN Optimization Solution

2009-12-29T18:00:00.000-08:00

You're evaluating your WAN (Wide Area Network) and wondering how you can optimize performance across the network. What are you're realistic options for a solution?

Keep in mind that this isn't necessarily a bandwidth solution, such as say MPLS or ethernet is. Rather it's a bandwidth utilization question.

I would suggest looking at WAN optimization appliances: Riverbed, Juniper, Packeteer. In many cases they do a very good job with latency, especially if the main source of the problem is CIFS WAN-unaware issues (copying/opening/modifying files using Windows).

The first step in my view is to find out the path your IP packets are taking. A delay can be caused if your connection is going through satellite and not a land line (Earthbound wireless, fibre- underwater or land, etc.).

First I would suggest tracing your packets' route ..... then making an SLA with your service provider and see if they can guarantee the quality parameters you want concerning BW, delay, jitter etc.

I wouldn't jump into buying or installing anything before that!

Keep in mind that all WAN-accelerators solve Latency issues. So choose any Vendor that does WAN-acceleration. But choosing the right one is not that easy. It depends on your WAN-traffic.

If you use applications (like Citrix, SAP) than a traffic priorizing Accelerator (Like Packeteer or Ipanema) will offer you the best results. However, if your traffic is more file oriented (MS-Office) ..... than you will get the best results with the Data reduction Accelerators, like Riverbed, Juniper Citrix and Cisco. In general you'll likely get the best results with Riverbed.

Wan Optimizations appliances have an effect only on TCP flows. If you have latency issues with UDP flows (voip) I don't think you can do anything against that (real time traffic is very sensitive to latency)

About generic TCP flows optimization, you'll find many vendors in the market selling products which fit well according to your needs : Citrix WanScaler, Cisco WAAS, Juniper, Riverbed, Expand and probably a lot of other vendors...

Here is the trick they all use to hide the effects of latency (they don't hide latency, because it already exists, they hide the effects), Wan optimization solutions act like a transparent TCP proxy, spoofing server's IP address to the client, and spoofing client's IP address to the server, and they send the TCP Ack messages locally. So you don't have to wait for the round trip time to get the ACK message. It helps to "fill-the-pipe" quickly. This is the great solution to avoid latency effects, as TCP throughput is highly sensitive to latency, due to the Ack return messages, also congestion control has an horrible effect when the TCP connections start.

Also they implement selective Acks and large initial flow control windows to use the total bandwidth of the WAN link. Add to this some compression mechanisms to artificially increase the bandwidth available and some layer 7 optimizations (mainly CIFS for file sharing, but also HTTP-based compression), embedded QoS stuff, and you have an overview of what we call "Wan optimization".

Whatever the vendor you choose, they all implement what I described above.

Michael is the owner of FreedomFire Communications... including DS3-Bandwidth.com. Michael also authors Broadband Nation where you're always welcome to drop in and catch up on the latest BroadBand news, tips, insights, and ramblings for the masses.

Are You Confident Your Application Will Work in the WAN?

2009-12-26T17:58:00.000-08:00

LANs vs. WANs

LANs are big, fast and reliable networks normally found within an organisation's main site or building (or the test lab). They can be rightly viewed as being super fast highways. The amount of data they carry is light relative to their capacity and the distances this data travels is relatively short. In contrast, WANs are geographically disbursed networks of often lower capacity which are required to carry a high volume of data compared with their capacity, over much greater distances.

There are three network key characteristics that influence an application's performance:

Available Bandwidth

WANs tend to have a much lower bandwidth than LANs which means that individual applications have to compete for space. This lower bandwidth can have a detrimental affect on software performance. Additionally, network administrators can set up their networks to favour certain applications like Voice over IP (VoIP) over 'conventional' applications, so once in the production environment the application is again competing for supremacy over others.

Latency

Latency is the delay encountered when running an application between two networks. It occurs because standard TCP/IP networks do not do not send data in a continuous stream, instead breaking it down into packets (like envelopes in the post) and sending it in batches. They also wait for confirmation that the packets have arrived safely before sending more, causing further delay. Also, the journey itself is not direct and various network devices will be encountered along the way, which all add their own additional delay. As a result, it can take 90ms to complete a round trip journey and an application transaction will consist of many such trips.

Packet Loss, Error and Reordering

As the packets of data travel over the network they can be lost, errored or reordered so that they arrive out of sequence, or don't arrive at all. It's like sending a bus down the road that either doesn't arrive or doesn't arrive entirely intact and is therefore probably useless when it reaches its destination. Wireless WAN, Satellite and 3G/Mobile Phone networks are generally subject to higher loss and error rates than wired networks. The increased use of wireless networks within buildings and as a way of allowing mobile 'on-the-road' members of the workforce to receive data means that applications need to be developed to cope with this potential for loss, erroring or reordering.

WAN emulation / network simulation

Reproducing these three network conditions is impossible if testing is confined to the internal LAN. However, WAN emulation / network simulation technology can be deployed in the same room as a normal test rig or even on a desktop. It allows the user to recreate a wide variety of different WAN or Wireless conditions and enables testing during prototype, development, quality assurance and pre-deployment stages.

A WAN emulator also gives complete control over the conditions in a single test in and also has the ability to reproduce these conditions time and again. This cannot be guaranteed if using a live network and additionally testing on a live network can interfere with existing mission-critical business applications already running.

Written by Phil Bull from iTrinegy, developers of sophisticated, yet easy-to-use, application response time monitoring, network traffic analysis and WAN/Network emulation technology to help organizations address networked application performance issues, de-risk application roll-outs and optimize network utilization.

What is a WAN Service and How Can it Help?

2009-12-19T17:50:00.000-08:00

A WAN, or Wide Area Network is a computer network that covers a large area, such as those whose communications need cross metropolitan, regional or national boundaries. A WAN is used to connect local area networks, or LANs and other networks together; the linking of these computers allows users and computers in one area to communicate with users and computers in another location.

Most WANs are designed for a single organisation and are privately used. Those that are built by ISP, Internet Service Providers, provide connections from various organisation LANs, or local area networks, to connect to the Internet, in this way, communications can be delivered over national boundaries.

These types of communications include;

* Instant messages
* Emails
* Real time auctions
* Online ordering placing

This in turn can reduce costs for companies by eliminating the need for travel and expensive long distance phone calls.

The benefits of using a WAN are that you can connect computers that are located over a vast area together. A network that can exchange data between sights is efficient and effective. The WAN enables computers to communicate with each other, some at different times and others at the same time. Not only can data be shared, but video as well, WANs are used for video conferencing and web casting. When communication is being shared between computers, each operator can access the same information at the same time.

When using a WAN, major corporations can reduce the branch office in house costs by enabling a centralised data centre to handle backup and storage resources. The use of a WAN also improves employee productivity by increasing and accelerating work applications as well as reducing replication across the WAN.

The use of private WANs have significant benefits also; the network is safe, secure and as it states, private. This type of network can reduce support and maintenance costs. There is an increased speed of the data that can be transmitted between sites because no other users are on the network. There is the ability to quickly access data that might be stored at different locations. This is also a great way for a company to provide training to their employees without the expense of airline tickets, hotels and providing meals for them.

As you can see, the benefits of having a WAN are vast. Whether you are using a private network to utilise quickness and efficiency between your satellite offices, or whether you are using a public WAN such as the Internet to purchase an item, communication between geographic areas is an important role in our society. Many people have used the Internet to gain knowledge by attending on-line college classes, or just have some fun playing an on-line interactive game; all of these activities were accessed using a WAN. The use of WANs offers opportunities never before possible for businesses as well as the everyday consumer.

Derek Rogers is a freelance writer who writes for a number of UK businesses. For Business Internet Services and WAN Services.

WAN Network Protocols - DSL, SONET, HDLC, DWDM, DLSW+

2009-12-17T17:47:00.001-08:00

Overview

This article discusses some of the most implemented WAN protocols in enterprise networking environments today including HDLC, DSL, SONET, DWDM, and DLSW+

High Level Data Link Control (HDLC)

HDLC is a Cisco proprietary protocol for designed for sending data across serial links. It defines an encapsulation method at the data link layer for transporting data over a public or private network. This protocol is utilized for Leased Line TDM circuits. TDM circuits are probably the oldest circuit types originating from circuit switching technology used by the public switched telephone network that carries your phone traffic. The difference is that companies transporting data traffic require circuit speeds of 256 Kbps to 45 Mbps. That is a data grade circuit which requires equipment at both ends of what is a phone line, for conditioning and formatting the data for those speeds.

The TDM network works with increments called digital signal zero's (DS-0). A DS-0 is a 64 Kbps channel (56 Kbps if in-band signaling used) that is part of the DS-1 industry standard specification. A DS-1 defines a framing standard for transmission across a T1 circuit at 1.544 Mbps with 24 DS-0 channels. A DS-3 defines a framing standard for transmission across a T3 circuit at 44.736 Mbps with 28 DS-1 channels. Some service providers offer what is called Fractional T1 (Frac T1). It is a circuit that runs at a speed less than 1.544 Mbps since it is a subset group of the 24 channels.

The common Fractional T1 speed is 384 Kbps, which is comprised of 6 DS-0 channels. Many router serial interfaces have a feature that split or channelize a T1 circuit. That is useful if you don't want to pay for a full T1 circuit. It does that by differentiating each specific channel from the full T1 circuit. Europe uses somewhat different circuit speed standards called E1and E3. The E1 circuit is comprised of 30 DS-0 channels and runs at 2.048 Mbps while E3 is comprised of 20 T1 channels and runs at 34.368 Mbps.

Digital Subscriber Line (DSL)

Digital Subscriber Line is a newer broadband technology being utilized for remote dial and access office connectivity. It is very cost effective when compared with ISDN and T1circuits since it is faster and less expensive. The issue with DSL is that you must be located no more than 18,000 feet from the service provider central office. The demand for high speed Internet access has service providers installing DSL terminating equipment at many central offices. That will increase the chances for availability in your neighborhood if it isn't an option today. The current specification defines three primary technologies, which are Asymmetric DSL (ADSL), Very High Data Rate DSL (VDSL) and Symmetric DSL (SDSL).

Asymmetric DSL (ADSL) as the name suggests is asymmetric technology, which allows faster downstream speeds from the service provider to the client than upstream speeds from the client to the service provider. That design matches the flow of Internet and video applications since they typically have the client downloading more information than sending it. Depending on the distance from the service provider central office, downstream speeds can be faster than 6 Mbps and upstream speeds can be as much as 640 Kbps. Being conservative with bridge taps and using increased wire diameter (gauge) will increase traffic rates as well from client to service provider.

The ADSL router or modem at the client will interface with a standard 2 pair telephone line, which is terminated at the service provider DSL Access Multiplexer (DSLAM). At that point the service provider will cross connect their DSLAM with a variety of different equipment such as T1, T3, SONET, Frame Relay, ATM or DSL circuits for transmission across the Internet or to a different central office. As mentioned some clients will utilize ADSL for line sharing their phone calls as well. The DSLAM will split off voice traffic from the data traffic and routed to a Class 5 switch where it is sent across the PSTN using a protocol such as SS7. Many business clients will opt for an additional data line, which is an increased cost however if the voice line isn't available that doesn't affect their Internet connection.

Very High Rate DSL (VDSL) is a higher speed DSL specification that will transmit data at distances between 1,000 feet and 4,500 feet across copper telephone lines. Distances of approximately 1000 feet will support speeds of 55 Mbps while distances of 4,500 feet will support an approximate speed of 12 Mbps. There are some technical differences with line encoding however the modem will split off the telephone service as does ADSL for phone calls.

Symmetric DSL (SDSL) is somewhat new and as the name suggests transmits data in both directions at T1 speeds. The distance specification from the central office is 21,000 feet and it should be noted that there must be a separate phone line since SDSL won't split off phone traffic. That is currently an issue that is being addressed and should be available this year. SDSL is an always-on service, which reduces the issues with call setup. That and the higher upstream traffic rates make it better suited for web hosting applications since your file downloads sent with downstream traffic is sent with their upstream traffic. There are tremendous opportunities for service providers to sell cost effective high speed Internet access to many clients across the United States today. Telecommuters and business clients can reduce costs with higher speed circuits for sending voice and data from home, access and distribution offices across the Internet.

SONET/SDH

The Synchronous Optical Network (SONET) specification describes a high speed fiber technology used by service providers for transporting voice and data traffic. A SONET network is built with a series of ring segments that are inter-connected. Each SONET segment is comprised of dual counter rotating rings for link diversity should one of the rings be unavailable. The standard OC-1 interface is 51.8 Mbps. The SONET network ring is built with Add/Drop Multiplexers (ADM) which terminate the SONET signal at various metropolitan and national locations. They are Time Division Multiplexers that mux/demux SONET signals from an OC-12 to OC-48 traffic stream. Each ADM has an active and a standby connection to the SONET ring. When a network failure with the active connection is detected, the standby connection is immediately activated. The SONET frame structure is 810 bytes that is comprised of overhead and payload bytes. The overhead is comprised of section and line signaling. The payload bytes are comprised of path signaling and payload. Customer routers such as the Cisco 7507 that support OC-3 interfaces that can interface with an ADM.

Dense Wave Division Multiplexing (DWDM)

Dense Wave Division Multiplexers (DWDM) are used to multiplex optical signals at various wavelengths onto a single fiber strand for transport across an optical network at speeds from OC-48 to OC-192. Each wavelength can run at speeds of up to 10 Gbps. Current optical systems can multiplex as many as 100 wavelengths or channels per fiber strand which is almost 1 Terabit (1000 Gbps) aggregate speed. Current efforts are focused on developing multi-terabit transport on 1 fiber strand. This technology is somewhat of a demarcation between the fastest enterprise core networks and the long haul ISP core networks which aggregate hundreds of enterprise customers. The enterprise customer can connect with DWDM networks using ATM switches and IP routers with OC-48 interfaces. Public and private SONET network providers have rings that connect using equipment with interfaces running at OC-48 speeds as well. The Cisco 12016 Gigabit switch router is available with OC-48 interfaces. Companies today are utilizing 400 OC-48 router interfaces at the 12016 to build a Terabit WAN core.

Data Link Switching (DLSW+)

Data Link Switching is a Layer 2 protocol used for encapsulating SNA frames across an IP WAN. It is an IP encapsulation method that integrates SNA workstations and servers with the IP enterprise network. Encapsulation of SNA is required since there is no Layer 3 addressing defined with its protocol stack. Routers that are configured with DLSW+ will establish peer relationships with local and remote DLSW+ routers. Each SNA Frame is encapsulated in an IP packet before it is sent across the WAN to a peer router configured with DLSW+. Each local router will terminate LLC2 data link layer frames from each workstation and send local acknowledgments to each local workstation as packets are sent and received. That eliminates LLC2 timeout issues that can occur between workstation and server when acknowledgments must travel across a congested WAN circuit.

SNA is connection-oriented and must receive data link acknowledgments every few seconds or the session will timeout. Bridge protocols such as Source Route Bridging (SRB) limit the number of bridges and rings that an SNA packet can span. There is no issue with the number of Rings utilized with DLSW+ since the RIF field is terminated at the router. DLSW+ integrates many different data link technologies such as Ethernet, Token Ring, SDLC and Frame Relay. There is a translation as well between different frame types such as Ethernet and Token Ring at each router for those data link technologies. Promiscuous mode is configured at DLSW+ routers which allows for many connections from remote peer routers. An example would be 7500 Data Center routers that have peer connections from many distribution offices.

Shaun Hummel is the author of Network Planning and Design Guide and has a web site focused on information technology job search solutions and certifications.

WAN Performance

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There is a practical solution for those you looking to improve your overall WAN performance. There are many enterprises the use WAN data optimization as a way to save money and get a handle on network congestion. Using a bandwidth optimization program like the Website Accelerator can reduce the amount of data transferred by up to 50%, increasing server performance, saving you money, and relieving stress throughout the WAN.

It’s only costing you money every moment your WAN bandwidth is not optimized. This is why using a program that handles all the optimizations automatically is such a practical solution. The Website Accelerator not only will install in minutes, but it supports a number of platforms.

• Sites based on Microsoft IIS technology such as SharePoint and ASP.NET can easily utilize the Website Accelerator through an ISAPI filter or ASP.NET module.
• Linux based servers will be able to utilize the Website Accelerator as an Apache module

Within minutes the software is configured and makes a number of changes to the outgoing data in order to increase performance.

By combining multiple files into one the Website Accelerator effectively reduces the amount of requests made on the server. By further compressing the combined data the content arrives much faster for the visitor, and reduces your page load times by up to 75%.

The Website Accelerator achieves this by combining JavaScript and CSS style sheets that are often spread out into multiple files. Using innovative technology the Website Accelerator also takes multiple images on a page and creates CSS sprite sheets, effectively turning several images into one optimized image. This does two things, reduces the amount of requests made through the WAN, and reduced the size of the data sent.

There is no need to be concerned with excess CPU usage caused by optimizing you WAN performance. the Website Accelerator has a robust caching system that will save a copy of the optimized page for serving; this ensures a page is only processed once. Once updated content is detected on a page the software will automatically update with the new optimized page.

The Website Accelerator easily integrates itself into your server and is preconfigured with optimizations out of the box, saving you countless man hours in the initial setup. The software is also compatible with a wide range of common JavaScript frameworks including the more popular AJAX, DotNetNuke, Microsoft SharePoint 2007 & CRM, and many more. Browser detection ensures further compatibility as the Website Accelerator will automatically detect which browser the visitor is using; this ensures no optimizations made will “break” the page.

The Website Accelerator reduces bandwidth costs by up to 50%, raises YSlow grade, and reduce page load times for your visitors. Amazing boosts in WAN performance, painless setup, and an affordable price point are what make the Website Accelerator a clear choice. The Website Accelerator literally takes minutes to install, configure, and test. This type of fast implementation allows for wide distribution through the WAN servers.