GE GE-DS-242-POE, User Manual

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Chapter 4: Web-Based Management
GE-DS-242-PoE Managed Ethernet Switch User Manual 99
Figure 4-57: QoS Configuration - Port-Based Priority
This page includes the following fields:
OBJECT DESCRIPTION
Port Number: Indicate port 1 to port 26.
Port Priority:
Each port has 8 priority levels—0~7 or Disable to be chosen. 7 is the
highest priority.
TOS/DSCP
TOS/DSCP priority is obtained through a 6-bit Type-of-Service (TOS) or Differentiated
Service Code Point (DSCP) to 3-bit priority mapping.
The Type of Service (TOS) octet in the IPv4 header is divided into three parts;
Precedence (3 bits), TOS (4 bits), and MBZ (1 bit). The Precedence bits indicate the
importance of a packet, whereas the TOS bits indicate how the network should make
tradeoffs between throughput, delay, reliability, and cost (as defined in RFC 1394). The
MBZ bit (for "must be zero") is currently unused and is either set to zero or just
ignored.
0 1 2 3 4 5 6 7
Precedence TOS MBZ
Pv4 Packet Header Type of Service Octet
The four TOS bits provide 15 different priority values, however only five values have a
defined meaning.