Terms and Definitions
February 22, 2008
Page 28 of 29
Matrix(su)->set policy rule admin-profile port ge.1.10 mask 16
port-string ge.1.10 admin-pid 2
Matrix(su)->set policy rule 1 tcpdestportIP 1720:10.0.0.1 cos 10
port-string ge.1.10
Matrix(su)->set cos port-resource irl 3.1 2 unit pps rate 5
Matrix(su)->set cos reference irl 3.1 10 rate-limit 1
Matrix(su)->set cos 10 priority 5 tos-value 184.0 txq-reference 8
irl-reference 2
Matrix(su)->set cos state enable
Terms and Definitions
Table 2
lists
terms
and
definitions
used
in
this
Quality
of
Service
configuration
discussion.
Table 2 Quality of Service Configuration Terms and Definitions
Term
Definition
Class of Service
(CoS)
The grouping of priority and forwarding behaviors that collectively determine packet
bandwidth behavior as it transits the link, including: 802.1p, IP ToS rewrite, priority
Transmit Queue (TxQ), Inbound and/or outbound Rate Limiter (IRL) and outbound
rate shaper.
DSCP
Differentiated Services Code Point. The lower 6 bits of the ToS field defined by RFC
2474.
Flows
In a QoS context, a sequence of IP packets that share a common class of service
and forwarding treatment as they transit the interface.
Forwarding
Treatment
Queue behavior during the packet egress stage (strict, Weighted Fair, Hybrid).
Jitter
The change in a flow’s packet spacing on the link due to the bursty and congestive
nature of the IP network. This irregular spacing - jitter - can severely degrade the
quality of voice calls or multimedia presentations.
Port Group
The grouping of ports based upon the same CoS features and port type.
Port Type
The differentiation of ports based upon TxQ and IRL resource capabilities.
Priority
The preference of one packet (classification) or queue (packet forwarding) over
another.
Quality of Service
(QoS)
A bandwidth management mechanism able to preferentially treat packets based
upon packet classification and forwarding treatment.
Rate Limiting
The bounding of bandwidth used by a QoS packet flow such that excess packets are
dropped/clipped.
Rate Shaping
The rescheduling of bursty traffic while in the queue based upon packet buffering
such that traffic beyond the configured bandwidth threshold is delayed until
bandwidth usage falls below the configured threshold.
Type of Service
(ToS)
An 8-bit field defined by RFC 1349 used for the prioritization of packets within a QoS
context.
