Most quality of service (QoS) schemes today are implemented to give priority to voice or video data running in common over a data circuit. The trick used to ensure that certain types of data receive priority over others makes use of a type of service (TOS) bit. Simply put, this is just a special flag inside of an Internet packet that can be a 1 or a 0, with a 1 implying priority while a 0 implies normal treatment.
In order for the TOS bit scheme to work correctly, all routers along a path need to be aware of it. In a self-contained corporate network, an organization usually controls all routers along the data path and makes sure that this recognition occurs. For example, a multinational organization with a VoIP system most likely purchases dedicated links through a global provider like ATT. In this scenario, the company can configure all of their routers to give priority to QoS tagged traffic, and this will prevent something like a print server file from degrading an interoffice VoIP call.
However, this can be a very expensive process and may not be available to smaller businesses and organizations that do not have their own dedicated links. In any place where many customers share an Internet link which is not the nailed up point-to-point that you’d find within a corporate network, there is contention for resources. In these cases, guaranteeing class of service is more difficult. So, this begs the question, “How can you set a QoS bit and prioritize traffic on such a link?”
In general, the answer is that you can’t.
The reason is quite simple. Your provider to the Internet cloud — Time Warner, Comcast, Qwest, etc. — most likely does not look at or support TOS bits. You can set them if you want, but they will probably be ignored. There are exceptions to this rule, however, but your voice traffic traveling over the Internet cloud will in all likelihood get the same treatment as all other traffic.
The good news is that most providers have plenty of bandwidth on their backbones and your third party voice service such as Skype will be fine. I personally use a PBX in the sky called Aptela from my home office. It works fine until my son starts watching YouTube videos and then all of a sudden my calls get choppy.
The bottle neck for this type of outage is not your provider’s backbone, but rather the limited link coming into your office or your home. The easiest way to ensure that your Skype call does not crash is to self-regulate the use of other bandwidth intensive Internet services.
Considering all of this, NetEqualizer customers often ask, “How does the NetEqualizer/AirEqualizer do priority QOS?”
It is a very unique technology, but the answer is also very simple. First, you need to clear your head about the way QoS is typically done in the Cisco™ model using bit tagging and such.
In its default mode, the NetEqualizer/AirEqualizer treats all of your standard traffic as one big pool. When your network is busy, it constantly readjusts bandwidth allocation for users automatically. It does this by temporarily limiting the amount of bandwidth a large download (such as that often found with p2p file sharing) might be using in order to ensure greater response times for e-mail, chat, Web browsing, VoIP, and other everyday online activities.
So, essentially, the NetEqualizer/AirEqualizer is already providing one level of QoS in the default setup. However, users have the option of giving certain applications priority over others.
For example, when you tell the NetEqualizer/AirEqualizer to give specific priority to your video server, it automatically squeezes all the other users into a smaller pool and leaves the video server traffic alone. In essence, this reserves bandwidth for the video server at a higher priority than all of the generic users. When the video stream is not active, the generic data users are allowed to utilize more bandwidth, including that which had been preserved for video. Once the settings are in place, all of this is done automatically and in real time. The same could be done with VoIP and other priority applications.
In most cases, the only users that even realize this process is taking place are those who are running the non-prioritized applications that have typically slowed your network. For everyone else, it’s business as usual. So, as mentioned, QoS over the NetEqualizer/AirEqualizer is ultimately a very simple process, but also very effective. And, it’s all done without controversial bit tagging and deep packet inspection!
April 15, 2009 at 5:07 AM
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