RS8234 Mindspeed Technologies, RS8234 Datasheet - Page 50

• Manufacturer Part Number: RS8234
• Description: Atm Servicesar Plus With Xbr Traffic Management
• Manufacturer: Mindspeed Technologies

2.0 Architecture Overview
2.5 Advanced xBR Traffic Management
2.5.1 CBR Traffic
2.5.2 VBR Traffic
2-18
The CBR service category requires guaranteed transmission rates, as well as
constrained CDV. The RS8234 facilitates these needs when generating CBR
traffic by pre-assigning specific schedule slots to CBR VCCs. For each CBR
assigned cell slot, the RS8234 generates a cell for that specific VCC unless data is
not available. The RS8234 also minimizes CDV by basing all traffic management
on a local reference clock.
CBR channel to the rate of its data source. The host may occasionally instruct the
xBR Scheduler to skip one transmit opportunity on a channel in order to
accomplish this rate-matching.
However, instead of one VCC, several UBR, VBR or ABR VCCs can be
scheduled within this CBR tunnel, in round-robin order.
of other service categories by the xBR Scheduler.
The RS8234 takes advantage of the asynchronous nature of ATM by reserving
bandwidth for VBR channels at average cell transmission rates without
pre-assigning “hardcoded” schedule slots, as with CBR traffic. This dynamic
scheduling allows VBR traffic to be statistically multiplexed onto the ATM line,
resulting in better utilization of the shared bandwidth resources. The xBR
Scheduler supports multiple priority levels for VBR traffic. Through the
combination of VBR parameters and priorities, it is possible to support real-time
VBR services.
GCRA algorithm. The GCRA I and L parameters control the per-VCC Peak Cell
Rate (PCR) and Cell Delay Variation Tolerance (CDVT) of the outgoing cell
stream on any channel. This guarantees compliance to policing algorithms
applied at the network ingress point. The user can control the granularity of rate
by dictating the number of schedule slots in the schedule table.
definitions. VBR1 controls PCR and CDVT. VBR2 controls PCR and CDVT, as
well as Sustained Cell Rate (SCR) and Burst Tolerance (BT). VBRC (also called
VBR3) controls PCR and CDVT on all cells, but controls SCR on only CLP = 0
(i.e., high priority) cells.
The RS8234 provides a mechanism to exactly match the scheduled rate of a
The RS8234 manages CBR tunnels in the same manner as a CBR VCC.
Unused CBR and Tunnel time slots are automatically made available to VCCs
The outgoing cell stream for each VBR VCC is scheduled according to the
Channels can be rate-shaped as VCs or VPs according to one of three VBR
Mindspeed Technologies
ATM ServiceSAR Plus with xBR Traffic Management
™
28234-DSH-001-B
RS8234