3onedata IES615-1F-2DI, Руководство пользователя

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User Manual
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The QoS technique developed by the working group, also known as class of service (CoS), is a 3-bit
field called the Priority Code Point (PCP) within an Ethernet frame header when using VLAN tagged
frames as defined by IEEE 802.1Q. It specifies a priority value of between 0 and 7 inclusive that can be
used by QoS disciplines to differentiate traffic. Although this technique is commonly referred to as
IEEE
802.1p , there is no standard or amendment by that name published by the IEEE. Rather the technique is
incorporated into IEEE 802.1Q standard which specifies the tag inserted into an Ethernet frame.
Priority levels
Eight different classes of service are available as expressed through the 3-bit PCP field in an IEEE
802.1Q header added to the frame. The way traffic is treated when assigned to any particular class is
undefined and left to the implementation. The IEEE however has made some broad recommendations:
PCP Priority Acronym Traffic Types
1 0 (lowest) BK Background
0 1 BE Best Effort
2 2 EE Excellent Effort
3 3 CA Critical Applications
4 4 VI Video, < 100 ms latency and jitter
5 5 VO Voice, < 10 ms latency and jitter
6 6 IC Internetwork Control
7 7 (highest) NC Network Control
(Figure 5.8.2.1)
5.8.3 TOS (DSCP)
TOS/DiffServ architecture provides each transport packets in the network are classified into different
categories, classified information is contained in the IP packet header, DiffServ architecture using the
first 6 bits of IP packet header TOS( Type of Service) to carry the packets' classified information. This
definition is only for the lower 6 bits, one number does not exceed 63. This definition supports both IPv4
(ToS field) and IPv6 (Traffic Class field). DSCP has 64 priority values (0-63), the lowest priority 0 and the
highest priority 63. In fact, the DSCP field is a superset of the IP precedence field, DSCP field definition
is backward-compatible with IP precedence field.
So far, the defined DSCP with default DSCP, the value is 0; class selector DSCP defined as the
backward-compatible with IP precedence, the value(8,16,24,32,40,48,56); Expedited Forwarding (EF),
generally used for low latency service, the recommended value is 46 (101110); identified by forwarding