
Industrial Managed
Ethernet Switch
User Manual
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The switch can classify traffic based on a valid 802
.
1p (CoS
-
Class of Service) priority tag. These options allow
users to map Priority Code Point (PCP) within an Ethernet frame header to different CoS priority queues as shown
in Figure 2.56. The user can choose the desired CoS Priority Queue from the drop
-
down list from Q1 to Q7 for each
PCP value. Descriptions of priority queue in CoS Queue Mapping page are summarized in Table 2.11.
Figure 2.56 Mapping Table of CoS Webpage
Table 2.11 Priority queue descriptions
Label
Description
Factory Default
PCP
Priority Code Point within the Ethernet frame header
.
PCP
0 is the lowest priority and 7 is the highest priority
.
PCP 0
-
> Q0
PCP 1
-
> Q0
PCP 2
-
> Q1
PCP 3
-
> Q1
PCP 4
-
> Q2
PCP 5
-
> Q2
PCP 6
-
> Q3
PCP 7
-
> Q3
CoS Priority
Queue
The priority queue from Q0 to Q7 that a specific Ethernet
frame needs to be assigned into
.
2.4.1.3
DSCP Mapping
DiffServ/ToS stands for Differentiated Services/Type of Services. It is a networking architecture that specifies a
simple but scalable mechanism for classifying network traffic and providing QoS guarantees on networks
.
DiffServ
uses a 6
-
bit Differentiated Service Code Point (DSCP) in the 8-bit differentiated services field (DS field) in the IP
header for packet classification purposes. The DS field and ECN field replace the outdated IPv4 TOS field in IPv4
to make per-hop behavior decisions about packet classification and traffic conditioning functions, such as metering,
marking, shaping, and policing.
The RFCs (Request for Comments) do not dictate the way to implement Per
-
Hop Behaviors (PHBs). Atop
implements queuing techniques that can base their PHB on the IP precedence or DSCP value in the IP header of
a packet. Based on DSCP or IP precedence, traffic can be put into a particular service class. Packets within a
service class are treated the same way.