Tcp Establishment Dscp Marking/ Set Ip Precedence/Dscp For Ntp - Cisco ASR 9000 Series Configuration Manual
Aggregation services router modular quality of service
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Configuring Modular QoS Service Packet Classification
TCP Establishment DSCP Marking/ Set IP Precedence/DSCP for NTP
The Differentiated Services Code Point (DSCP) field in an IP packet which helps enables different levels of
service to be assigned to network traffic. Marking is a process, which helps to modify QOS fields incoming
and outgoing packets. You can use marking commands in traffic classes, which are referenced in the policy
map. You can configure the following marking features:
• DSCP
• IP Precedence
• CoS
Each IP packet is marked with a DSCP code and assigned to corresponding level of service. DSCP is a
combination of IP Precedence and Type of Service fields. The TCP Establishment DSCP Marking/Set IP
Precedence feature sets Network Time Protocol (NTP) with the DSCP field. NTP packets can be based on
either IPv4 and IPV6 based respectively. The NTP sets DSCP/TOS field under either v4 or v6 IP headers.
The DSCP level can be configured through the NTP configuration. The configured level will be set across
NTP packets throughout IP layer.
IP Precedence Compared to IP DSCP Marking
If you need to mark packets in your network and all your devices support IP DSCP marking, use the IP DSCP
marking to mark your packets because the IP DSCP markings provide more unconditional packet marking
options. If marking by IP DSCP is undesirable, however, or if you are unsure if the devices in your network
support IP DSCP values, use the IP precedence value to mark your packets. The IP precedence value is likely
to be supported by all devices in the network.
You can set up to 8 different IP precedence markings and 64 different IP DSCP markings.
Configuring DSCP for source IPv4 address for NTP Packets
To mark a packet by setting the IP DSCP value for NTP packets, use the following commands (given below)
starting in global configuration mode. These commands permit configuring the DSCP for source addresses,
to mark NTP packets, so that the marked NTP packets are treated as per the DSCP markings. There are
different code point values available for different services:
SUMMARY STEPS
1. configure
2. ntp {ipv4} dscp
3. end or commit
4. show processes ntpd
5. show ntp associations
Cisco ASR 9000 Series Aggregation Services Router Modular Quality of Service Configuration Guide, Release 6.1.x
TCP Establishment DSCP Marking/ Set IP Precedence/DSCP for NTP
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