Tripp Lite NGI-M08C4-L2, Руководство пользователя

Страница: 65 / 313

65
All Ports 802.1p
priority
Use this field to set a priority for all ports.
The value indicates packet priority and is added to the priority tag
field of incoming packets. The values range from 0 (lowest priority)
to 7 (highest priority).
Port This field displays the number of a port.
802.1p Priority
Select a priority for packets received by the port. Only packets
without 802.1p priority tagged will be applied the priority you set
here.
Apply Click Apply to take effect the settings.
Refresh Click Refresh to begin configuring this screen afresh.
6.1.1.2 IP DiffServ (DSCP)
DiffServ (DSCP)
Differentiated Services or DiffServ is a computer networking architecture that specifies a
simple, scalable and coarse-grained mechanism for classifying, managing network traffic and
providing Quality of Service ( QoS ) guarantees on modern IP networks. DiffServ can, for
example, be used to provide low-latency, guaranteed service (
GS
) to critical network traffic such
as voice or video while providing simple best-effort traffic guarantees to non-critical services
such as web traffic or file transfers.
Differentiated Services Code Point ( DSCP ) is a 6-bit field in the header of IP packets for packet
classification purposes. DSCP replaces the outdated IP precedence, a 3-bit field in the Type of
Service byte of the IP header originally used to classify and prioritize types of traffic.
When using the DiffServ priority mechanism, the packet is classified based on the DSCP field in
the IP header. If the tag is present, the packet is assigned to a programmable egress queue based
on the value of the tagged priority. The tagged priority can be designated to any of the available
queues.
Version IHL
Type of Service
Total Length
Identification Flags Fragment Offset
Time to Live Protocol Header Checksum
Source Address
Destination Address
Options Padding
Example Internet Datagram Header
IP Header Type of Service: 8 bits
The Type of Service provides an indication of the abstract parameters of the quality of service
desired. These parameters are to be used to guide the selection of the actual service parameters
when transmitting a datagram through a particular network. Several networks offer service
precedence, which somehow treats high precedence traffic as more important than other traffic
(generally by accepting only traffic above certain precedence at time of high load). The major