3Com 3C10200 NBX Installation Guide - Page 85
Before You Begin Installation, NBX System Quality of Service, Low-bandwidth Connections - compression
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Before You Begin Installation 85 NBX System Quality of Service Quality of Service (QoS) is a way to allocate resources in data switches and routers so that data can be prioritized, with the most time-critical data receiving higher priority. At Layer 2, the NBX system supports Ethernet 802.1Q, "Standard for Virtual Bridged Local Area Networks," and its associated specification, 802.1P, "Standard for Local and Metropolitan Area Networks, Supplement to Media Access Control (MAC) Bridges: Traffic Class Expediting and Dynamic Multicast Filtering." These IEEE Ethernet standards define how Ethernet packets can be prioritized. At Layer 3, the NBX supports IP Precedence, also called IP Type Of Service (ToS), to specify the class of service for each packet. The default hexadecimal value for NBX system IP ToS settings is 0xb8. Low-bandwidth Connections You can configure a telephone to operate in lower-bandwidth environments such as a single B channel of a BRI ISDN line or other links with bandwidth as low as 56 Kbps. ■ The preferred method for enabling a low-bandwidth connection is to select G729 audio, forcing the device to use lower-bandwidth compressed audio when communicating with other system devices. ■ Alternatively, you can configure the telephone as a low-bandwidth device by disabling some of the internal features such as paging, conferencing, and music-on-hold. A check box in the NBX NetSet device configuration screen (Telephone Configuration > Telephones) automatically selects the best parameters for low-bandwidth connections. You can also connect an NBX Telephone to the system over a broadband connection and that is not considered a low-bandwidth connection. See the NBX Administrator's Guide for information about connecting a remote telephone over a broadband connection. Before You Begin Installation Before you install the NBX system hardware: ■ Complete the system plan. See the System Planning Guide on the NBX Resource Pack. ■ Verify that the external telephone lines are active and present at the installation location.