Overview - HP ProCurve Switch 6120G/XG Management Manual

Term Use in This Document
outbound port For any port, a buffer that holds outbound traffic until it can leave the switch through that port. By
queue default, there are eight outbound queues for each port in the switch. Queue 8 is the highest priority
queue; queue 1 is the lowest priority queue. Traffic in a port's high priority queue leaves the switch
before any traffic in the port's medium or low priority queues.
re-marking Assigns a new QoS policy to an outbound packet by changing the DSCP bit settings in the ToS byte.
(DSCP re-
marking)
tagged port Identifies a port as belonging to a specific VLAN and enables VLAN-tagged packets belonging to that
membership VLAN to carry an 802.1p priority setting when outbound from that port. Where a port is an untagged
member of a VLAN, outbound packets belonging to that VLAN do not carry an 802.1p priority setting.
Type-of-Service Comprised of a three-bit (high-order) precedence field and a five-bit (low-order) Type-of-Service field.
(ToS) byte Later implementations may use this byte as a six-bit (high-order) Differentiated Services field and a
two-bit (low-order) reserved field. See also "IP-precedence bits" and DSCP elsewhere in this table.
upstream A device linked directly or indirectly to an inbound switch port. That is, the switch receives traffic from
device upstream devices.

Overview

QoS settings operate on two levels:
Controlling the priority of outbound packets moving through the
■
switch: Each switch port has four shared outbound traffic queues; the
queue with a priority value of one has the lowest priority, and priority
value four has the highest priority. Packets leave the switch port on the
basis of their queue assignment and whether any higher queues are empty:
Table 5-1. Port Queue Exit Priorities
Port Queue and
802.1p Priority Values
Low (1)
Low (2)
Normal (0)
Normal (3)
Medium (4)
Medium (5)
High (6)
High (7)
Quality of Service (QoS): Managing Bandwidth More Effectively
Priority for Exiting
From the Port
Fourth
Third
Second
First
Introduction
5-7