Lucent Technologies PacketStar PSAX, User Manual

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255-700-243 B-31
PacketStar
®
PSAX 12-Port Medium-Density DS1 Multiservice Module User Guide , Issue 1 Release 8.0
Appendix B Reference Information
Quality of Service (QoS) Information Tables
Table B-10 illustrates the attributes of the classes of service supported by the
PSAX system software.
The following tables illustrate how ATM classes of service correspond to
internal priority levels as the AQueMan algorithm functions. Table B-11
identifies the cell loss and cell delay tolerance of each service class, with
internal priorities. Table B-12 lists the class-of-service choices available when
configuring PVC connections on a PSAX system and shows service examples
for each PVC connection type. The service examples in Table B-12 are
intended simply as illustrations and you should choose your service class
Table B-9. PSAX System-Supported Quality of Service Classes
ATM Service Class Description
Constant Bit Rate (CBR) This service operates on a connection basis and offers consistent delay
predictability. CBR is used for applications such as circuit emulation,
voice, and video.
Variable Bit Rate—Real
Time (VBR-RT) This service operates on a connection basis and offers very low delay
variance but requires access to a variable amount of network band-
width. VBR-RT is used for such applications as packet video and
voice.
Variable Bit Rate—Non-
real Time (VBR-NRT) This service operates on both a connection and connectionless basis
and allows delay variance between the delivery of cells. VBR-NRT is
used for data applications that have potentially bursty traffic charac-
teristics, including LAN interconnections, CAD/CAM, and multime-
dia. This class can be used to support switched multimegabit data ser-
vice (SMDS).
Unspecified Bit Rate (UBR) This service operates on a connection basis and allows for raw cell or
best-effort transport by the network. In UBR service, cells are trans-
ported by the network whenever bandwidth is available and traffic is
presented by the user. Data using UBR service is more apt to be dis-
carded during peak traffic times in deference to data using other
classes of service.
Table B-10. Class of Service Descriptions
Constant Bit
Rate (CBR)
Variable Bit
Rate Real Time
(VBR-RT)
Variable Bit Rate
Non-real Time
(VBR-NRT)
Unspecified Bit
Rate (UBR)
QoS Class Class 1 Class 2 Classes 3, 4 Class 5
Applications Voice and
video Packet video
and voice Data
Bit Rate Constant Variable
Timing Required at
Source or Destination Required Not required
Service Examples Private line Compressed
voice Frame relay,
switched multi-
media data service Raw cell, Ethernet
AAL 1 2 3/4 and 5 3/4 and 5