D-Link DSL-2640B - Manual (Page 20)

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Find out the following values from your ISP before you change them.
• VPI: Virtual Path Identifier. The valid range is 0 to 255.
• VCI: Virtual Channel Identifier. The valid range is 32 to 65535.
• Service Category: Five classes of traffic are listed—
o UBR Without PCR (Unspecified Bit Rate without Peak Cell Rate)—
UBR service is suitable for applications that can tolerate variable
delays and some cell losses. Applications suitable for UBR service
include text/data/image transfer, messaging, distribution, and
retrieval and also for remote terminal applications such as
telecommuting.
o UBR With PCR (Unspecified Bit Rate with Peak Cell Rate)--
o CBR (Constant Bit Rate)—used by applications that require a fixed
data rate that is continuously available during the connection time.
It is commonly used for uncompressed audio and video information
such as videoconferencing, interactive audio (telephony), audio /
video distribution (e.g. television, distance learning, and pay-per-
view), and audio / video retrieval (e.g. video-on-demand and audio
library).
o Non Realtime VBR (Non-Real-time Variable Bit Rate)—can be used
for data transfers that have critical response-time requirements
such as airline reservations, banking transactions, and process
monitoring.
o Realtime VBR (Real-time Variable Bit Rate)—used by time-sensitive
applications such as real-time video. Rt-VBR service allows the
network more flexibility than CBR.
• Quality of Service: Can be enabled only for UBR without PCR, UBR with
PCR, and Non Realtime VPR.