Motorola WMC6300 用户手册
User Priority Settings and Quality of Service Overview
Classification of Data Packets
The MEA system uses two methods to classify data packets in order to provide them the
requested levels of service. The first is the use of the industry-standard Differentiated Services
Code Point (DSCP). The second is a proprietary system based on the assigned priority of the
node’s user.
requested levels of service. The first is the use of the industry-standard Differentiated Services
Code Point (DSCP). The second is a proprietary system based on the assigned priority of the
node’s user.
Differentiated Services Code Point
The DSCP is defined in RFC 2474 as a part of the Differentiated Services (DS, or “DiffServ”)
field. This field is defined for both the IPv4 and IPv6 headers. The DSCP is a dimensionless
number used to index a particular class of traffic and, thereby, a particular transport behavior at
each hop. These behaviors are known as Per-Hop Behaviors (PHBs).
field. This field is defined for both the IPv4 and IPv6 headers. The DSCP is a dimensionless
number used to index a particular class of traffic and, thereby, a particular transport behavior at
each hop. These behaviors are known as Per-Hop Behaviors (PHBs).
Some basic code points are defined in RFC 2474 for backwards compatibility with the
overlapping “Precedence” field in the IPv4 header, known collectively as Class Selector Code
Points. Extensions to these, called Assured Forwarding and Expedited Forwarding classes, are
defined in RFCs 2597 and 2598. Other groups of code points are reserved for experimental or
site-local use.
overlapping “Precedence” field in the IPv4 header, known collectively as Class Selector Code
Points. Extensions to these, called Assured Forwarding and Expedited Forwarding classes, are
defined in RFCs 2597 and 2598. Other groups of code points are reserved for experimental or
site-local use.
Most often, the indexed per-hop behaviors are described (and sometimes, implemented) simply
in terms of queue prioritization of packets at each hop. However, the behaviors may incorporate
other features such as traffic pruning to condition the traffic flowing from the node.
in terms of queue prioritization of packets at each hop. However, the behaviors may incorporate
other features such as traffic pruning to condition the traffic flowing from the node.
For example, voice packets may be assigned a DSCP tag indicating the need for low-latency
service. The transport can then intelligently decide to discard stale packets or prioritize new
packets to provide the lowest latency possible while, perhaps, sacrificing raw bandwidth or
reliability when the demand exceeds capacity. High priority data transfers might be tagged to
indicate the need for high reliability. The transport can use this knowledge to increase buffering
or provide extra retries, perhaps increasing the stream’s latency but serving the data reliably.
Likewise, bulk data packets can be assigned “best effort” service so that the transport layer can
intersperse them between packets needing lower latency or higher bandwidth.
service. The transport can then intelligently decide to discard stale packets or prioritize new
packets to provide the lowest latency possible while, perhaps, sacrificing raw bandwidth or
reliability when the demand exceeds capacity. High priority data transfers might be tagged to
indicate the need for high reliability. The transport can use this knowledge to increase buffering
or provide extra retries, perhaps increasing the stream’s latency but serving the data reliably.
Likewise, bulk data packets can be assigned “best effort” service so that the transport layer can
intersperse them between packets needing lower latency or higher bandwidth.
The MEA system extracts the DS field from IP packets as they enter the wireless mesh, either
at the access point or at the subscriber device. The DSCP classification then serves as one of
the inputs for selecting an appropriate behavior in the transport mechanisms.
at the access point or at the subscriber device. The DSCP classification then serves as one of
the inputs for selecting an appropriate behavior in the transport mechanisms.
User Priority
The MEA QoS system also augments the standards-based DSCP traffic classification system
with a proprietary feature to implement hierarchical service on a per-user basis. While DSCP
can be used to classify the traffic by payload, the User Priority feature classifies traffic by the
user that originated it, tagging packets with an assigned priority level. Using this tag, data
packets from high priority nodes can be granted preferential service over packets from lower
priority nodes.
with a proprietary feature to implement hierarchical service on a per-user basis. While DSCP
can be used to classify the traffic by payload, the User Priority feature classifies traffic by the
user that originated it, tagging packets with an assigned priority level. Using this tag, data
packets from high priority nodes can be granted preferential service over packets from lower
priority nodes.
The User Priority at each node is a managed variable with tight control granted to the Network
Administrator through the Device Manager utilities available in MeshManager. The user on the
WMC6300 node is free to select a priority level through applications using the MeshAPI
software interface. However, the Network Administrator through the Device Manager can put
bounds on each node, limiting the node’s user priority to a specific range or setting it to a
specific value.
Administrator through the Device Manager utilities available in MeshManager. The user on the
WMC6300 node is free to select a priority level through applications using the MeshAPI
software interface. However, the Network Administrator through the Device Manager can put
bounds on each node, limiting the node’s user priority to a specific range or setting it to a
specific value.
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