Controlling the dial-up bandwidth on your VPN

Managing available bandwidth via dial-up connectivity was once a relatively easy task for network administrators. Previously, most users connected to a virtual private network, or VPN, via the Internet using connections that consumed only a small amount of bandwidth. With the onset of broadband communications such as cable and DSL within SOHO environments, however, administrators now face the challenge of controlling available bandwidth on VPNs.

If your telecommuters are burning bandwidth by using broadband connectivity, how can you address this problem? Here are some solutions available to network administrators that can help limit and control the amount of bandwidth used, both inside and outside of the network.

Quality of Service for all
Improved firewalls and routers, incorporating Quality of Service (QoS), enable the limitation of bandwidth for incoming and outgoing data, which in turn increases acceptable performance for each employee outside of the office, no matter the connection speed.



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Definition: Quality of Service
In networking, Quality of Service (QoS) is a term that indicates a guaranteed bandwidth level.
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With QoS integrated within a VPN, an administrator gains full control over the data flowing through the network. Two ways to maintain this control are packet classification and bandwidth management:
Packet classification
Packet classification groups data by importance. The more important the data, the higher its classification, and the better handling it receives at the expense of other, less important data on the same network.
Bandwidth management
By using bandwidth management, a VPN administrator can police the incoming and outgoing data from a network and allow certain amounts of bandwidth to be available for differing packet classifications.
Other forms of bandwidth control
Depending on the needs of the network administrator, there are additional ways of controlling the amount of available bandwidth:
Traffic shaping
Traffic shaping comes into play when a service provider detects Internet traffic congestion. The amount of incoming and outgoing data streams is then lowered via queuing. This causes the bandwidth in use to fall below the allowed allocation.
Fair bandwidth
Fair bandwidth allows all users on a network to obtain equal access to Internet bandwidth. With fair bandwidth enabled, applications using large amounts of a data stream, such as MP3s, will have their bandwidth decreased in order to provide fair access to other employees.
Guaranteed delivery
Guaranteed delivery reserves a section of bandwidth for specific services within a network, such as video teleconferencing, voiceover IP, and money transactions. It determines which services are high priority and allocates bandwidth accordingly.

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Read more about virtual private networks
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Controlling bandwidth will continue to challenge administrators
Network administrators must control virtual private networking and the resources that are required for it to operate successfully in an organization. Because telecommuters and remote offices are here to stay, VPN administrators will continue to have issues with maintaining bandwidth. However, the incorporation of new technologies intended to supplement QoS will help network administrators manage this problem.

Article resources
The following resources were used in the creation of this article:
Ashley Laurent Security Newsletter―Volume 1, Issue 2, 3/3/00
Access VPNs for the Enterprise―Cisco Systems, 7/3/000
Quality of Service for Virtual Private Networks―Cisco Systems, 8/28/00
QoS definition by Webopedia

作个SOHO吧。