Cambium Networks PTP 450 Series, Руководство по настройке

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Chapter 1: Configuration Configuring quality of service
Page
1-245
The number of data channels available on the AP is still limited to 238 in release 15.2 This could be 238
SM’s each configured with a single Low Priority channel, or, for example, 59 SMs with 4 data channels
configured and 1 SM with 2 data channels configured.
A module prioritizes traffic by:
• reading the 802.1p field of the 802.1Q header in a received packet, where VLAN is enabled on the
module.
• comparing the 6-bit Differentiated Services Code Point (DSCP) field in the ToS byte of a received
packet to a corresponding value in the Diffserv tab of the Configuration page of the module.
Modules monitor ToS bytes with DSCP fields, but with the following differences:
• The 6-bit length of the field allows it to specify one of 64 service differentiations.
• These correlate to 64 individual (CodePoint) parameters in the Diffserv tab of the Configuration
page.
• The 8 Class Selector code points are fixed in code and not user settable.
• For any or all of the remaining 56 CodePoint parameters, you can specify a value of
o
0, 1 for low-priority handling.
o
2, 3 for medium-priority handling.
o
4,5 for high-priority handling.
o
6, 7 for ultra-high-priority handling.
The above mapping applies if 4 QoS levels are configured. If fewer than that are configured, see the
mapping table in the
IPv4 and IPv6 Prioritization of this document.
Note
Ensure that your Differentiated Services domain boundary nodes mark any entering packet,
as needed, so that it specifies the appropriate Code Point for that traffic and domain. This
prevents theft of service level.
An example of the Diffserv page in the Configuration menu and parameter descriptions are provided
under
DiffServ attributes – AP/BHM on page 1-63 . This tab and its rules are identical from module type
to module type. However, any of the 61 configurable Code Points can be set to a different value from
module to module, thus defining unique per-hop behavior for some traffic.
This tab in the AP sets the priorities for the various packets in the downstream (sent from the public
network). This tab in the SM sets the priorities for the various packets in the upstream (sent to the
public network).
Typically, some SMs attach to older devices that use the ToS byte as originally formatted, and others to
newer devices that use the DSCP field. The
default values in the Diffserv page allow your modules to
prioritize traffic from the older devices roughly the same as they traditionally have. However, these
default values may result in more high-priority traffic as DSCP fields from the newer devices are read
and handled. So, after making changes in the Diffserv page, carefully monitor the high-priority channel
for high packet rates
• in SMs that you have identified as those to initially set and watch.
• across your network when you have broadly implemented Code Point values, such as via SNMP.