User guide

EDA System Services
64 1/1551-HSC 901 35/3 Uen C 2005-12-02
the management traffic will use a hidden UBR PVC (a ninth PVC if eight
other PVCs are used for End-user traffic).
Class of Service (CoS)
Data (Best Effort)0-4
Video (Video Multicast)5
Voice (Telephony over IP)6
Management7
Service QueuesClassification
(p-bit)
Max 8*PVC per
ADSL connection
CPE
Ethernet VLAN
IEEE 802.1Q
Management
System
Video SP 1
ISP 1
P: 6
Voice
Voice
Video
Video
P: 5
Data
Data
P: 0
Management
Management
P: 7
IAD
IP
DSLAM
Ethernet
Switch
Voice
Gateway
VBR-rt
UBR
VBR-nrt
Figure 46 Service Mapping and QoS in EDA
QoS in the ATM network uses the following features to ensure the fastest
possible transmission of voice traffic over the ADSL line:
• Priority and service classes
• Segmentation
• Burst allowance
Priority is implemented by creating Permanent Virtual Circuits (PVCs) for
voice, video and data on each ADSL line. Each PVC is like an open
connection in a traditional circuit switched network.
Voice PVCs are configured with the service class VBR-rt (Variable Bit Rate
real-time). The service class requires strictly controlled delays and delay
variations, but not necessarily a constant bandwidth. It is characterized by
Peak Cell Rate (PCR), Sustainable Cell Rate (SCR) and Maximum Burst
Size (MBS) / Burst Tolerance (BT).
The Peak Cell Rate defines the maximum bit rate (kbps) that may be
transmitted in the PVC. The Maximum Burst Size/Burst Tolerance is the
number of cells or maximum time for which data may be transmitted at the
Peak Cell Rate. The PCR and MBS or BT thus defines what is called burst