How to enter qos packages. What's the most efficient way to completely disable QoS? Disable QoS via registry

In this article, we'll take a look at how to configure the reserved bandwidth in Windows 10. By default, Windows reserves 20% of the total Internet bandwidth.

Yes, yes, the Windows 10 operating system reserves a certain percentage of your Internet connection bandwidth for quality of service (QoS).

According to Microsoft:

QoS can include critical system operations such as updating the Windows system, managing the licensing status, etc. The concept of reserved bandwidth applies to all programs running on the system. Typically the packet scheduler will limit the system to 80% of the connectivity bandwidth. This means that Windows reserves 20% of your Internet bandwidth exclusively for QoS.

In case you want to get that reserved percentage of bandwidth, this article is for you. Below are two ways to configure the reserved bandwidth in the Windows 10 operating system.

NOTE: If you turn off all the reserved bandwidth for your system, that is, set it to 0%, this will affect the actions of the operating system, especially automatic updates.

Denial of responsibility: further steps will include editing the registry. Errors while editing the registry can adversely affect your system. Therefore, be careful when editing registry entries and create a system restore point first.

Step 1: Open Registry Editor(if you are not familiar with the registry editor click).

Step 2: In the left pane of the Registry Editor window, navigate to the following section:

HKEY_LOCAL_MACHINE \ SOFTWARE \ Policies \ Microsoft \ Windows \ Psched

Note: If the section and parameter " NonBestEffortLimit"Don't exist, just create them.

Step 3: Now in the right pane of the registry key "Psched" find the DWORD (32 bit) parameter named NonBestEffortLimit... Double click on it to change its values:

By default, the parameter is set to 50 in hexadecimal or 80 in decimal notation.

Step 4: Select the decimal system and set the value equal to the percentage of the required reserved bandwidth.

For example if you set the value to be 0 , the reserved bandwidth for your Windows operating system will be completely disabled, i.e. equal to 0%. Click the button "OK" and close the registry editor.

Step 5: Restart your PC for the changes to take effect.

If you want to configure or limit the reserved bandwidth on multiple computers in your organization / workplace, you can deploy the appropriate setting in the GPO.

Step 1: Open the Local Group Policy Editor

Step 2: Go to the section: Computer Configuration → Administrative Templates → Network → Qos Package Scheduler

Step 3: In the right window, double-click the policy.

By default, this policy is not set and the system reserves 20% bandwidth of the Internet connection. You need to enable it, set the parameter "Limit the reserved bandwidth" meaning "Included".

Is it possible to speed up the Internet at all? Easily! Below is a simple set of measures that can significantly increase the speed of the Internet in Windows.

Acceleration potential

For example, if you have 10 megabytes per second in your contract with your provider, then in reality you will get a download speed somewhere at the level of 1 megabyte per second, or even lower. The fact is that the QoS service is running on Windows, which maybe reserve up to 20% speed for your tasks. The browser also waits for a response from DNS servers. And in advanced cases, the browser may have hardware accelerated page rendering disabled. And then the web-surfing turns into torment. Therefore, if you disable QoS, enable caching of DNS requests and enable hardware acceleration in the browser, the speed of the Internet can increase significantly.

The easiest way to speed up Internet on Windows

The easiest and safest way to disable QoS and add 20% to speed is to edit the security policy. You do not need to go into the registry and risk the performance of the entire computer, it is enough to uncheck one box in the convenient settings editor.

So, click "Start" → "Run" and enter the name: gpedit.msc. The Security Policy Editor will open. We sequentially go along the following route: "Computer Configuration" → "Administrative Templates" → "Network" → " QoS Packet Scheduler". Enable Limit Reserved Bandwidth, but enter 0% as a fallback. Ready.

Increase DNS cache to speed up the network

The role of the DNS cache is to store the IP addresses of all Internet sites that you visit most often. If you have a tendency to visit certain Internet resources very often (for example, social networks VK, Facebook, Twiter, various blogs or multimedia resources YouTube, StumbleUpon), then an increase in your browser's DNS cache should positively affect the loading speed of these Internet pages. To increase the cache size, you need to do the following:

Click on the "Start" button, type in the search word "regedit" and press the Enter key. You should start the registry editor. Further in the editor, you need to go to the following path:

HKEY_LOCAL_MACHINE \ SYSTEM \ CurrentControlSet \ Services \ DNScache \ Parameters

CacheHashTableBucketSize
CacheHashTableSize
MaxCacheEntryTtlLimit
MaxSOACacheEntryTtlLimit

And assign them the following values:

CacheHashTableBucketSize - set to 1
CacheHashTableSize - set to 384
MaxCacheEntryTtlLimit - set to 64000
MaxSOACacheEntryTtlLimit - set to 301

Speed ​​up the Internet by disabling QoS

As far as it became known, in XP, Vista, Windows 7, 8 and 10 there is a system for reserving the width of the Internet channel. This system (QoS Reserved Bandwidth Limit) deliberately restricts your traffic to allow normal operation and traffic of higher priority applications such as Update Center or other priority components. The reserved channel width is about 20% of the maximum speed of your internet. That is, with this limitation, you actually use only 80% of the speed that your provider provides. Therefore, changing this percentage can significantly speed up your browser and the loading of Internet pages. In order to reduce the width of the reserved channel in Windows 7, follow these steps:

As in the previous case, click on the "Start" button, type in the search word "regedit" and press the Enter key. You should start the registry editor. Further in the editor, you must go to the following path:

HKEY_LOCAL_MACHINE \ SOFTWARE \ Policies \ Microsoft

Now, with the right mouse button on the newly created key in the left part of the window, create a new parameter of type “DWORD” and name it “NonBestEffortLimit”. To disable channel reservation, set the "NonBestEffortLimit" key to "0".

Disable auto-tuning of ТСР

In Windows 7, the auto-tuning function is enabled by default. This function can be one of the reasons why some individual sites or Internet services can load slowly, since this function does not work effectively with a large number of servers with different access speeds. In order to disable automatic tuning of ТСР, it is necessary to start the command line on behalf of the administrator and enter the following command into it:

Netsh interface tcp set global autotuninglevel = disabled

In order to return the auto-tuning of ТСР back, it is necessary to enter the following command in the command line (run as administrator):

Netsh interface tcp set global autotuninglevel = normal

And then restart the computer in the same way.

Browser hardware acceleration

In some cases, you may have noticed that the browsing of certain certain Internet pages from your browser is much slower than in previous versions of the same browser. This may be due to the fact that your browser is currently using software rendering mode by default instead of GPU rendering mode (that is, rendering using hardware accelerated GPU rendering). This can happen to users who have outdated video cards or drivers for them, which in turn do not support or no longer support GPU hardware acceleration. A possible solution to this problem is to install the latest video adapter driver that supports GPU hardware acceleration.

If this problem was not solved by installing the latest driver for the video card, then the only way out of this situation may be to replace the current video card with a newer one that will support hardware acceleration using the GPU.

But you can make sure in which mode your browser is running. This, as a rule, can be viewed in the advanced settings of the browser, and more specifically the hardware acceleration option.

Internet Explorer:

1. Open Internet Explorer and go to the settings menu “Tools -> Internet Options”.
2. On the Advanced tab, you should see an option to accelerate graphics.

Now make sure to check the box next to Use software rendering instead of GPU rendering. If checked, then Internet Explorer uses software rendering mode. Uncheck the box if you want IE to go into GPU rendering mode. If this option is grayed out and does not change, then your video card or its driver does not support hardware acceleration for the browser.

An example of how to see if hardware acceleration is enabled for Mozilla Firefox:

1. Launch Firefox and open browser preferences using the “Tools -> Preferences” menu.
2. Click on the “Advanced” tab, where on the “General” tab you should see a “Browsing” section. In this section there is an option named “Use hardware acceleration when available”. If this option is not checked, then your browser uses software rendering mode. Check the box to have Firefox start using hardware acceleration if your graphics subsystem supports it.

How to speed up internet in Windows 8 using NameBench

When your browser tries to visit a site, it first contacts the DNS name server. The problem is that this server is physically located at your ISP. What are small commercial companies famous for? That's right - the desire to save on everything. Therefore, the equipment for the DNS service is bought weak. Well, you are trying to enter the site, the browser accesses the slow DNS server of the provider, and then there is a delay, which can be several seconds. Now, remember that each page of the site can contain pictures, videos, Flash, etc. from other sites. These are again DNS queries to the slow server. As a result, losses add up and braking becomes noticeable. What to do? The obvious answer is to use the fastest DNS servers. Find them and the program helps NameBench.

What are we waiting for? Download NameBench (free) and run it. No installation required. Once launched, select your country, browser used and click the Start Benchmark button. The program will try several dozen DNS servers and choose the fastest one for you. On average, you can find a server that is 2-3 times faster than your ISP's DNS.

After NameBench finds the fastest DNS, you will be shown the IP address of that server. It also needs to be registered in the connection settings. Everything is as usual:

You will be pleasantly surprised when you notice that the Internet works much faster!

One of the most popular areas in today's networking is the mixing of voice and video over traditional data networks. One of the problems with this kind of information is that for it to work properly, video and audio data packets must be transmitted to the recipient quickly and reliably, without interruptions or too long delays. However, at the same time, this type of traffic should not impede the transmission of more traditional data packets.

One possible solution to this problem is QoS. QoS, or quality of service, is a technology for prioritizing data packets. QoS allows you to transmit time-sensitive packets with a higher priority than other packets.

QoS is an industry standard, not a Microsoft standard. However, Microsoft first introduced this QoS standard in Windows 2000. Microsoft's version of QoS has evolved quite a bit since then, but still meets industry standards.

In Windows XP Professional, QoS primarily acts as a bandwidth reservation mechanism. When QoS is enabled, the application is allowed to reserve up to 20% of the total network bandwidth provided by each machine's NIC. However, the amount of network bandwidth that the application reserves is configurable. I'll show you how to change the amount of bandwidth reserved in part three.

To see how the spare bandwidth is being used, suppose you have a video conferencing application that requires prioritized bandwidth to function properly. Assuming QoS is enabled for this application, we can say that it reserves 20% of the machine's total bandwidth, leaving 80% of the bandwidth for the rest of the network traffic.

All applications, except video conferencing applications, use a technology called best effort delivery. This means that packets are sent with the same first-delivered-first-served priority. On the other hand, video conferencing application traffic will always be prioritized over other traffic, but the application will never be allowed to consume more than 20% of all bandwidth.

However, just because Windows XP reserves some of the bandwidth for priority traffic does not mean that applications with normal priority will not be able to use the spare bandwidth. While video conferencing applications take advantage of the higher priority reserved bandwidth, the chances of such applications being constantly used are very small. In this case, Windows allows other applications to use the spare and non-spare bandwidth for the best possible delivery, as long as the applications for which a portion of the network bandwidth is reserved are not used.

As soon as the video conferencing application starts, Windows starts to enforce the reservation. Even so, the reservation is not absolute. Suppose Windows has reserved 20% of the network bandwidth for a video conferencing application, but this application does not need all 20%. In these cases, Windows allows other applications to use the remaining bandwidth, but will continually monitor the needs of the higher priority application. In case the application needs more bandwidth, the bandwidth will be allocated to it up to a maximum value of 20%.

As I said before, QoS is an industry standard, not a Microsoft technology. As such, QoS is used by Windows, but Windows cannot do the job on its own. For QoS to work, every piece of equipment between the sender and receiver must support QoS. This means that network adapters, switches, routers and all other devices in use need to know about QoS, as well as the operating systems of the recipient and sender.

If you're curious, then you don't need to install some crazy exotic network infrastructure to use QoS. Asynchronous Transfer Mode (ATM) is an excellent networking technology for using QoS as it is a connection-oriented technology, however you can use QoS with other technologies such as Frame Relay, Ethernet, and even Wi-FI (802.11 x).

The reason ATM is such an ideal choice for QoS is because it is capable of implementing bandwidth reservation and resource allocation at the hardware level. This type of distribution goes beyond the capabilities of Ethernet and similar networking technologies. This does not mean that QoS cannot be used. It just means that QoS should be applied differently from ATM.

In an ATM environment, resources are allocated immediately, at the physical device level. Since Ethernet and other similar technologies cannot allocate resources in this way, this type of technology is based on prioritization rather than true resource allocation. This means that bandwidth reservations occur at the higher layer of the OSI model. Once the bandwidth has been reserved, the higher priority packets are sent first.

One point to consider if you are going to apply QoS over Ethernet, Wi-Fi, or other similar technologies is that such technologies are unconnected. This means that there is no way for the sender to check the status of the receiver or the status of the network between the sender and the receiver. This, in turn, means that the sender can guarantee that the higher priority packets will be sent first, but cannot guarantee that these packets will be delivered within a certain time frame. On the other hand, QoS can provide this kind of assurance on ATM networks, since ATM is a connection-oriented technology.

Windows 2000 vs. Windows Server 2003

Earlier, I talked about how Microsoft first introduced QoS in Windows 2000, and that this application of QoS has evolved significantly since that time. Therefore, I want to talk a little about the differences between QoS in Windows 2000 and in Windows XP and Windows Server 2003 (in which this standard is used approximately the same).

In Windows 2000, QoS was based on the Intserv architecture, which is not supported in Windows XP or Windows Server 2003. The reason Microsoft chose not to use such an architecture was that the underlying API was difficult to use and the architecture had problems. with scale.

Some organizations still use Windows 2000, so I decided to give you some information on how the Windows 2000 QoS architecture works. Windows 2000 uses a protocol called RSVP to reserve bandwidth resources. When bandwidth is requested, Windows needs to determine when packets can be sent. To do this, Windows 2000 uses a signaling protocol called SBM (Sunbelt Bandwidth manager) to tell the sender that it is ready to receive packets. The Admission Control Service (ACS) verifies that effective bandwidth is available and then either grants or denies the bandwidth request.

Traffic management API

One of the main problems with prioritizing network traffic is that you cannot prioritize traffic based on the computer that generates it. It is common for single computers to use multiple applications, and create a separate traffic stream for each application (and operating system). When this happens, each traffic stream must be prioritized individually. After all, one application may need spare bandwidth, while the best delivery is ideal for another application.

This is where the Traffic Control API (Traffic Control Programming Interface) comes into play. The Traffic Control API is an application programming interface that allows you to apply QoS parameters to individual packages. The Traffic Control API works by defining individual traffic streams and applying different QoS control methods to those streams.

The first thing the Traffic Control API does is create what is known as filterspec. Filterspec is essentially a filter that defines what it means for a package to belong to a particular stream. Some of the attributes used by the filterspec include the source and destination IP address of the packet and the port number.

Once the filterspec has been defined, the API allows you to create flowspec. Flowspec defines the QoS parameters that will be applied to the sequence of packets. Some of the parameters defined by the flowspec include the transfer rate (acceptable transfer rate) and the type of service.

The third concept defined by the Traffic Control API is the flow concept. A flow is a simple sequence of packets that are subject to the same flowspec. In simple terms, the filterspec defines which packages will be included in the flowspec. Flowspec determines whether packets will be processed with higher priorities, and flow is the actual transfer of packets that are processed by the flowspec. All packets in the stream are processed equally.

It should be mentioned that one of the advantages of the Traffic Control API over the Generic QoS API used in Windows 2000 is the ability to use aggregation (aggregation). If a node has multiple applications transmitting multiple data streams to a common destination, then these packets can be combined into a common stream. This is true even if the applications use different port numbers, provided that the source and destination IP addresses are the same.

Generic Packet Classifier

In the previous section, I discussed the relationship between flowspec, filterspec, and flow. However, it is important to remember that the Traffic Control API is simply an application programming interface. As such, its job is to define and prioritize traffic flows, not create those flows.

The Generic Packet Classifier is responsible for creating streams. As you recall from the previous section, one of the attributes that was defined in the flowspec was the service type. The service type essentially determines the priority of the thread. The Generic Packet Classifier is responsible for determining the type of service that has been assigned to the flowspec, after which it queues the associated packets according to the type of service. Each thread is placed in a separate queue.

QoS Packet Scheduler

The third QoS component you need to be aware of is the QoS Packet Scheduler. Simply put, the primary job of the QoS Packet Scheduler is traffic shaping. To do this, the packet scheduler receives packets from various queues, and then marks these packets with priorities and flow rates.

As I discussed in the first part of this article series, for QoS to work correctly, the various components located between the source of packets and their destination must support (i.e. be aware of) QoS. While these devices need to know how to deal with QoS, they also need to know how to handle normal traffic without priorities. To make this possible, QoS uses a technology called tagging.

In fact, there are two types of markings here. The QoS Packet Scheduler uses Diffserv tagging, which is recognized by Layer 3 devices, and 802.1p tagging, which is recognized by Layer 2 devices.

Configuring the QoS Packet Scheduler

Before I show you how tagging works, it should be noted that you will need to configure the QoS packet scheduler for everything to work. In Windows Server 2003, the QoS Packet Scheduler is an optional networking component, just like the Client for Microsoft Networks or the TCP / IP protocol. To enable QoS Packet Scheduler, open the properties page of your server's network connection and check the box next to QoS Packet Scheduler, as shown in Figure A. If the QoS Packet Scheduler is not listed, click the Install button and follow the instructions.

Figure A: QoS Packet Scheduler must be enabled before you can use QoS

Another thing you need to know about the QoS Packet Scheduler is that your network adapter must support 802.1p tagging for it to work properly. To test your adapter, click the Configure button, Figure A, and Windows will display the properties for your network adapter. If you look at the Advanced tab on the property page, you will see the various properties that your network adapter supports.

If you look at Figure B, you can see that 802.1Q / 1P VLAN Tagging is one of the properties listed. You can also see that this property is disabled by default. To enable 802.1p tagging, simply enable this property and click OK.

Figure B: You must enable 802.1Q / 1P VLAN Tagging

You may have noticed in Figure B that the property you enabled is VLAN tagging, not packet tagging. This is because priority markers are included in VLAN tags. The 802.1Q standard defines VLANs and VLAN tags. This standard actually reserves three bits in the VLAN packet, which are used to write the priority code. Unfortunately, the 802.1Q standard never specifies what these priority codes should be.

The 802.1P standard was created to complement 802.1Q. 802.1P defines the priority tagging that can be enclosed in a VLAN tag.

802.1P signal

As I said in the previous part, 802.1p signaling is carried out at the second layer of the OSI model. This layer is used by physical devices such as switches. Layer 2 devices that support 802.1p can view the priority markings that are assigned to packets and then group those packets into separate traffic classes.

On Ethernet networks, priority marking is included in VLAN tags. VLANs and VLAN tags are defined by the 802.1Q standard, which defines a three-bit priority field, but does not really define how this priority field should be used. This is where the 802.1P standard comes into play.

802.1P defines various priority classes that can be used in conjunction with the 802.1Q standard. Ultimately 802.1Q leaves it up to the administrator to choose the priority marking, so technically you don't need to follow 802.1P's guidelines, but 802.1P seems to be the one that everyone chooses.

While the idea of ​​using 802.1P standards to provide layer 2 marking probably sounds like pure theory, it can actually be defined using Group Policy settings. The 802.1P standard provides eight different priority classes (ranging from 0 to 7). Higher priority packets are processed by QoS with higher delivery priority.

By default, Microsoft assigns the following priority markings:

But as I mentioned earlier, you can change these priorities by modifying various Group Policy settings. To do this, open the Group Policy Editor and navigate in the console tree to the Computer Configuration \ Administration Templates \ Networks \ QoS Package Scheduler \ Second-Level Priority Value. As you can see in Figure A, there are Group Policy settings corresponding to each of the priority labels I listed above. You can assign your own priority marking levels to any of these service types. Keep in mind, however, that these Group Policy settings only apply to hosts running Windows XP, 2003, or Vista.

Figure A: You can use the Group Policy Editor to customize second-level priority marking.

Differentiated Services

As I explained in the previous article, QoS performs priority marking at the second and third layers of the OSI model. This ensures that priorities are taken into account throughout the package delivery process. For example, switches operate at layer 2 of the OSI model, but routers typically operate at layer 3. Thus, if the packets used only 802.1p priority marking, the switch would prioritize these packets, but the network routers would ignore these priorities. To counter this, QoS uses the Differentiated Services protocol (Diffserv) to prioritize traffic on the third layer of the OSI model. Diffserv marking is included in the IP headers of packets using TCP / IP.

The architecture used by Diffserv was originally defined by RFC 2475. However, many of the architecture specifications have been rewritten in RFC 2474. RFC 2474 defines the Diffserv architecture for IPv4 and IPv6.

An interesting point about IPv4 in RFC 2474 is that even though Diffserv has been completely redefined, it is still backward compatible with the original RFC 2475 specification. This means that older routers that do not support the new specifications can recognize the assigned priorities.

The current Diffserv application uses the Type of Service (TOS) packet type octets to store the Diffserv value (called the DSCP value). Within this octet, the first six bits hold the DSCP value, and the last two bits are unused. The reason these markings are backward compatible with the RFC 2475 specification is because RFC 2475 required the first three bits in the same octet to be used in IP sequence information. Although the DSCP values ​​are six bits in length, the first three bits still reflect the IP sequence.

As with the 802.1p tagging that I demonstrated earlier, you can configure Diffserv priorities through various Group Policy settings. Before I show you how, I will introduce the standard Diffserv priorities used in Windows:

You may have noticed that Diffserv priority markings use a completely different range than 802.1P. Instead of supporting a range of 0-7, Diffserv supports a priority marking range from 0 to 63, with larger numbers having higher priorities.

As I said before, Windows allows you to define Diffserv priority marking using Group Policy settings. Keep in mind, however, that some more advanced routers will assign their own Diffserv values ​​to packets, regardless of what Windows has assigned.

With this in mind, you can configure Diffserv Priority Marking by opening the Group Policy Editor and navigating to Computer Configuration \ Administrative Templates \ Network \ QoS Package Scheduler in the console tree.

If you look at Figure B, you will notice that there are two DSCP related tabs under the QoS Packet Scheduler tab. One of these tabs allows you to assign DSCP priority marking for packets that match the flowspec, and the other allows you to set DSCP priority marking for non-compliant packets. The actual parameters themselves are similar for both tabs, as shown in Figure C.

Figure B: Windows manages DSCP priority markings separately for packets that match the flowspec and those that don't.

Figure C: You can manually assign DSCP priority marking for different types of services.

Diverse Group Policy Settings

If you look at Figure B, you will notice that there are three Group Policy settings that I did not mention. I wanted to briefly mention what these parameters are and what they do, for those who might be interested.

The Limit Outstanding Packets parameter is essentially a service threshold value. If the number of surpassed packets reaches a certain value, then QoS will deny any additional bandwidth allocation for the network adapter until the value falls below the maximum allowed threshold.

The Limit Reservable Bandwidth parameter controls the percentage of total bandwidth that QoS-enabled applications can reserve. By default, QoS-enabled applications can reserve up to 80% of the network bandwidth. Of course, any portion of the bandwidth that is reserved that is not currently being used by QoS applications can be used by other applications.

The Set Timer Resolution parameter controls the minimum time units (in microseconds) that the QoS packet scheduler will use to schedule packets. Essentially, this setting controls the maximum rate at which packets can be queued for delivery.

QoS and modems

In this age of almost universal availability of broadband technologies, it seems strange to talk about modems. However, there are still many small businesses and home users who use modems as a mechanism to connect to the Internet. Recently I even saw a large corporation using modems to communicate with satellite offices that are located in remote locations where broadband technology is not available.

Of course, the biggest problem with using modems is the limited bandwidth they have. A less obvious but equally important issue is that users generally do not change their online behavior when using dial-up connections. Of course, users may not feel much like downloading large files when connected to the Internet via a modem, but the rest of the user behavior remains the same as if they were connected via a broadband connection.

Typically, users don't worry too much about keeping Microsoft Outlook open all the time, or browsing while files are downloading in the background. Some users also keep their instant messaging system open at all times. The problem with this type of behavior is that each of these applications or tasks consumes a certain amount of bandwidth on your internet connection.

To see how QoS can help, let's take a look at what happens under normal circumstances when QoS is not used. Typically, the first application that tries to access the internet has the most rights to use the connection. This does not mean that other applications cannot use the connection, but rather that Windows thinks that other applications will not use the connection.

Once the connection is established, Windows starts dynamically adjusting the TCP receive window size. The TCP receive window size is the amount of data that can be sent before waiting for an acknowledgment that the data has been received. The larger the TCP receive window, the larger the packets that the sender can transmit before waiting for a successful delivery confirmation.

The TCP receive window size must be tuned carefully. If TCP's receive window is too small, efficiency will suffer, as TCP requires very frequent acknowledgments. However, if the TCP receive window is too large, then the machine may transmit too much data before it knows that there was a problem during the transfer. As a result, large amounts of data are required to be retransmitted, which also impacts efficiency.

When an application starts using a dial-up Internet connection, Windows dynamically adjusts the TCP receive window size as it sends packets. The goal of Windows here is to achieve a stable state in which the TCP receive window size is optimally tuned.

Now, suppose the user opens a second app that also requires an internet connection. After it does so, Windows initiates the TCP slow start algorithm, which is the algorithm that is responsible for adjusting the TCP receive window size to the optimal value. The problem is that TCP is already in use by an application that was launched earlier. This affects the second application in two ways. First, the second application takes much longer to achieve the optimal TCP receive window size. Second, the baud rate for the second application will always be slower than the baud rate for the forward running application.

The good news is that you can avoid these problems on Windows XP and Windows Server 2003 by simply running the QOS Package Scheduler. After that, the QOS Packet Scheduler will automatically use a technology called Deficit Round Robin whenever Windows detects a slow connection speed.

Deficit Round Robin works by dynamically creating separate queues for each application that needs access to the Internet. Windows serves these queues in a round robin fashion that dramatically improves the efficiency of all applications that need to access the Internet. If you're curious, Deficit Round Robin is also available in Windows 2000 Server, but it doesn't automatically turn on.

Internet connection sharing

In Windows XP and Windows Server 2003, QoS also facilitates Internet connection sharing. As you probably know, Internet connection sharing is a simplified NAT-based router. The computer to which the Internet connection is physically connected acts as a router and DHCP server for other computers on the network, thereby providing them with access to the Internet through this host. Internet connection sharing is typically only used in small, peer-to-peer networks that lack domain infrastructure. Large networks typically use physical routers or routing and remote access services.

In the section above, I have already explained how Windows dynamically adjusts the TCP receive window size. However, this dynamic setting can cause problems when sharing an Internet connection. The reason for this is that connections between computers on a local network are usually relatively fast. Typically, such a connection consists of 100 Mb Ethernet, or 802.11G wireless. While these types of connections are far from the fastest, they are much faster than most Internet connections available in the United States. This is where the problem lies.

The client computer needs to communicate over the Internet, but it cannot do this directly. Instead, it uses the internet connection sharing host as an access module. When Windows calculates the optimal TCP receive window size, it does so based on the speed of the connection between the local machine and the Internet Connection Sharing machine. The difference between the amount of data that the local machine can actually receive from the Internet and the amount that it thinks it can receive, based on the speed of the Internet Connection Sharing host, can cause problems. More specifically, the difference in connection speed can potentially cause situations in which data is backed up in a queue connected to a slow connection.

This is where QoS comes into play. If you install the QOS Packet Scheduler on an Internet Connection Sharing site, the Internet Connection Sharing host will invalidate the TCP receive window size. This means that the Internet Connection Sharing host will set the TCP receive window size for local hosts to the same size as they would if they were directly connected to the Internet. This fixes problems caused by network connection speed mismatches.

Conclusion

In this article series, I have covered QoS and how it can be used to shape traffic flow across different types of network connections. As you can see, QoS can make the network work much more efficiently by shaping traffic in such a way that it can take advantage of the lightest network congestion and ensure faster delivery of higher priority traffic.

Brien Posey

In the first part of this series, I covered what QoS does and what it is used for. In this part I will continue the conversation by explaining how QoS works. As you read this article, please keep in mind that the information presented here is based on the Windows Server 2003 QoS application, which is different from the QoS application in Windows 2000 Server.

Traffic management API

One of the main problems with prioritizing network traffic is that you cannot prioritize traffic based on the computer that generates it. It is common for single computers to use multiple applications, and create a separate traffic stream for each application (and operating system). When this happens, each traffic stream must be prioritized individually. After all, one application may need spare bandwidth, while the best delivery is ideal for another application.

This is where the Traffic Control API (Traffic Control Programming Interface) comes into play. The Traffic Control API is an application programming interface that allows you to apply QoS parameters to individual packages. The Traffic Control API works by defining individual traffic streams and applying different QoS control methods to those streams.

The first thing the Traffic Control API does is create what is known as filterspec. Filterspec is essentially a filter that defines what it means for a package to belong to a particular stream. Some of the attributes used by the filterspec include the source and destination IP address of the packet and the port number.

Once the filterspec has been defined, the API allows you to create flowspec. Flowspec defines the QoS parameters that will be applied to the sequence of packets. Some of the parameters defined by the flowspec include the transfer rate (acceptable transfer rate) and the type of service.

The third concept defined by the Traffic Control API is the flow concept. A flow is a simple sequence of packets that are subject to the same flowspec. In simple terms, the filterspec defines which packages will be included in the flowspec. Flowspec determines whether packets will be processed with higher priorities, and flow is the actual transfer of packets that are processed by the flowspec. All packets in the stream are processed equally.

It should be mentioned that one of the advantages of the Traffic Control API over the Generic QoS API used in Windows 2000 is the ability to use aggregation (aggregation). If a node has multiple applications transmitting multiple data streams to a common destination, then these packets can be combined into a common stream. This is true even if the applications use different port numbers, provided that the source and destination IP addresses are the same.

Generic Packet Classifier

In the previous section, I discussed the relationship between flowspec, filterspec, and flow. However, it is important to remember that the Traffic Control API is simply an application programming interface. As such, its job is to define and prioritize traffic flows, not create those flows.

The Generic Packet Classifier is responsible for creating streams. As you recall from the previous section, one of the attributes that was defined in the flowspec was the service type. The service type essentially determines the priority of the thread. The Generic Packet Classifier is responsible for determining the type of service that has been assigned to the flowspec, after which it queues the associated packets according to the type of service. Each thread is placed in a separate queue.

QoS Packet Scheduler

The third QoS component you need to be aware of is the QoS Packet Scheduler. Simply put, the primary job of the QoS Packet Scheduler is traffic shaping. To do this, the packet scheduler receives packets from various queues, and then marks these packets with priorities and flow rates.

As I discussed in the first part of this article series, for QoS to work correctly, the various components located between the source of packets and their destination must support (i.e. be aware of) QoS. While these devices need to know how to deal with QoS, they also need to know how to handle normal traffic without priorities. To make this possible, QoS uses a technology called tagging.

In fact, there are two types of markings here. The QoS Packet Scheduler uses Diffserv tagging, which is recognized by Layer 3 devices, and 802.1p tagging, which is recognized by Layer 2 devices.

Configuring the QoS Packet Scheduler

Before I show you how tagging works, it should be noted that you will need to configure the QoS packet scheduler for everything to work. In Windows Server 2003, the QoS Packet Scheduler is an optional networking component, just like the Client for Microsoft Networks or the TCP / IP protocol. To enable QoS Packet Scheduler, open the properties page of your server's network connection and check the box next to QoS Packet Scheduler, as shown in Figure A. If the QoS Packet Scheduler is not listed, click the Install button and follow the instructions.

Figure A: QoS Packet Scheduler must be enabled before you can use QoS

Another thing you need to know about the QoS Packet Scheduler is that your network adapter must support 802.1p tagging for it to work properly. To test your adapter, click the Configure button, Figure A, and Windows will display the properties for your network adapter. If you look at the Advanced tab on the property page, you will see the various properties that your network adapter supports.

If you look at Figure B, you can see that 802.1Q / 1P VLAN Tagging is one of the properties listed. You can also see that this property is disabled by default. To enable 802.1p tagging, simply enable this property and click OK.

Figure B: You must enable 802.1Q / 1P VLAN Tagging

You may have noticed in Figure B that the property you enabled is VLAN tagging, not packet tagging. This is because priority markers are included in VLAN tags. The 802.1Q standard defines VLANs and VLAN tags. This standard actually reserves three bits in the VLAN packet, which are used to write the priority code. Unfortunately, the 802.1Q standard never specifies what these priority codes should be.

The 802.1P standard was created to complement 802.1Q. 802.1P defines the priority tagging that can be enclosed in a VLAN tag. I'll tell you how these two standards work in part three.

Conclusion

In this article, we discussed some of the basic concepts in Windows Server 2003's QoS architecture. In Part 3, I'll go into more detail on how the QoS Packet Scheduler marks packets. I will also discuss how QoS works in a low bandwidth network environment.