Upstream Scheduler
Mode
This document describes how to configure optional upstream (US)
scheduler modes.
With this feature, you can select Unsolicited Grant Services (UGS),
Real Time Polling Service (rtPS) or Non-Real Time Polling Service (nrtPS)
scheduling types, as well as packet-based or Time Division Multiplex (TDM)
based scheduling. Low latency queuing (LLQ) emulates a packet-mode-like
operation over the TDM infrastructure of DOCSIS. As such, the feature provides
the typical trade-off between packets and TDM. With LLQ, you have more
flexibility in defining service parameters for UGS, rtPS or nrtPS, but with no
guarantee (other than statistical distribution) regarding parameters such as
delay and jitter.
Finding Feature Information
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the Feature Information Table at the end of this document.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to http://tools.cisco.com/ITDIT/CFN/. An account on http://www.cisco.com/ is not required.
Hardware
Compatibility Matrix for Cisco cBR Series Routers
 Note |
The hardware
components introduced in a given Cisco IOS-XE Release are supported in all
subsequent releases unless otherwise specified.
|
Table 1 Hardware Compatibility Matrix for the Cisco cBR Series Routers
Cisco CMTS Platform
|
Processor Engine
|
Interface Cards
|
Cisco cBR-8 Converged Broadband Router
|
Cisco IOS-XE Release 16.5.1 and Later Releases
Cisco cBR-8
Supervisor:
-
PID—CBR-CCAP-SUP-160G
-
PID—CBR-CCAP-SUP-60G
-
PID—CBR-SUP-8X10G-PIC
|
Cisco IOS-XE Release 16.5.1 and Later Releases
Cisco cBR-8 CCAP Line Cards:
-
PID—CBR-LC-8D30-16U30
-
PID—CBR-LC-8D31-16U30
-
PID—CBR-RF-PIC
-
PID—CBR-RF-PROT-PIC
-
PID—CBR-CCAP-LC-40G-R
Cisco cBR-8 Downstream PHY Modules:
-
PID—CBR-D30-DS-MOD
-
PID—CBR-D31-DS-MOD
Cisco cBR-8 Upstream PHY Modules:
|
Restrictions for
Upstream Scheduler Mode
-
To ensure proper operation, Interface-based Admission Control
must be enabled. When the LLQ option is enabled, it is possible for the
upstream path to be filled with so many calls that it becomes unusable, making
voice quality unacceptable. Interface-based admission control must be used to
limit the number of calls to ensure acceptable voice quality, as well as to
ensure traffic other than voice traffic.
-
Even if Interface-based admission control is not enabled, the
default (DOCSIS)scheduling mode blocks traffic after a certain number of calls.
-
UGS with Activity Detection (UGS-AD) is not supported by the LLQ
scheduler mode but remains supported by the default DOCSIS scheduler mode.
Information About
Upstream Scheduler Mode for the Cisco CMTS Routers
With UGS, a service
flow is created that enables a cable modem to transmit fixed-size bursts of
data at a guaranteed rate and with a guaranteed level of jitter by providing
periodic transmission opportunities to the cable modem for fixed-sized frames.
This kind of service flow is particularly suitable for VoIP applications.
With rtPS, a
service flow is created that provides a periodic opportunity for a cable modem
to request permission to transmit data by polling a single cable modem for a
bandwidth request, rather than all the cable modems. This satisfies
applications that have a requirement for real-time data transmission, and
enables the cable modem to transmit data bursts of varying length. This kind of
service flow is particularly suitable for MPEG VoIP.
The rtPS requests, by default, are
internally treated as priority 7—the highest priority for all Best Effort
traffic. This high priority reduces the latency of rtPS traffic under
congestion.
With nrtPS, a
service flow is created that provides a periodic opportunity for a cable modem
to request permission to transmit data by polling a single cable modem for a
bandwidth request, rather than all the cable modems. The data bursts may be of
varying length. This kind of service flow is particularly suitable for
non-interactive services such as file transfers.
How to Configure
Upstream Scheduler Modes
Procedure | Command or Action | Purpose |
---|
Step 1 | enable
Example:
Router> enable
|
Enables
privileged EXEC mode.
- Enter your password if
prompted.
|
Step 2 | configure
terminal
Example:
Router# configure terminal
|
Enters global
configuration mode.
|
Step 3 | Use one the
following commands:
Example:
Router(config)# interface cable 7/0/1
|
Enters
interface configuration mode for the specified cable interface.
|
Step 4 | cable upstream
n
scheduling type ugs
mode
[llq
|docsis]
Example:
Router(config-if)# cable upstream 4 scheduling type ugs mode llq
|
Enables
LLQ-type (packet-based) scheduling for UGS services.
Note
| Any
combination of
ugs,
rtps,
nrtps,
llq, and
docsis
is allowed. The only default value is
docsis
.
|
|
Step 5 |
cable upstream
n
scheduling
type rtps mode
[llq
|docsis]
Example:
Router(config-if)# cable upstream 4 scheduling type rtps mode docsis
|
Enables
standard DOCSIS (TDM-based) scheduling for rtPS services.
Note
| Any
combination of
ugs,
rtps,
nrtps,
llq, and
docsis
is allowed. The only default value is
docsis
.
|
|
Step 6 | end
Example:
Router(config-if)# end
|
Exits
interface configuration mode and returns to privileged EXEC mode.
|
What to Do Next
To confirm whether the scheduler is
operating in DOCSIS mode, use the show interface cable
mac-scheduler command.
Router# show interface cable 7/0/1 mac-scheduler 0
DOCSIS 1.1 MAC scheduler for Cable7/0/1/U0 : rate 30720000
wfq:None
us_balance:OFF
fairness:OFF
Queue[Rng Polls] flows 0
Queue[CIR Grants] flows 0
Queue[BE(07) Grants] flows 0
Queue[BE(06) Grants] flows 0
Queue[BE(05) Grants] flows 0
Queue[BE(04) Grants] flows 0
Queue[BE(03) Grants] flows 0
Queue[BE(02) Grants] flows 0
Queue[BE(01) Grants] flows 0
Queue[BE(00) Grants] flows 0
Req Slots 2601578997, Req/Data Slots 4484512
Init Mtn Slots 38265829, Stn Mtn Slots 78753
Short Grant Slots 0, Long Grant Slots 0
Adv Phy Short Grant Slots 412, Adv Phy Long Grant Slots 5519087
Adv Phy UGS Grant Slots 0
Avg upstream channel utilization : 1%
Avg percent contention slots : 98%
Avg percent initial ranging slots : 1%
Avg percent minislots lost on late MAPs : 0%
MAP TSS: lch_state 9, init_retries 0
late_initial_maps 0, late_ucd_maps 0
mac-phy tss errors 0, missed ccc 0
Additional
References
The following
sections provide references related to the Cisco CMTS routers.
Standards
Standard
|
Title
|
DOCSIS
|
Data-Over-Cable Service Interface Specifications, DOCSIS 2.0, Radio Frequency
Interface Specification, CM-SP-RFIv2.0-I08-050408
|
Technical
Assistance
Description
|
Link
|
The
Cisco Support and Documentation website provides online resources to download
documentation, software, and tools. Use these resources to install and
configure the software and to troubleshoot and resolve technical issues with
Cisco products and technologies. Access to most tools on the Cisco Support and
Documentation website requires a Cisco.com user ID and password.
|
http://www.cisco.com/cisco/web/support/index.html
|
Feature Information for Upstream Scheduler Mode
Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
 Note |
The table below lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
|
Table 2 Feature Information for Upstream Scheduler Mode
Feature Name
|
Releases
|
Feature Information
|
Upstream Scheduler Mode
|
Cisco IOS XE Everest 16.5.1
|
This feature was integrated into Cisco IOS XE Everest 16.5.1 on the Cisco cBR Series Converged Broadband Routers.
|