Dell PowerConnect 7000 Series, Reference Manual

Page: 645 / 1730

QoS Commands
645
31
QoS Commands
Quality of Service (QoS) technologies are intended to provide guaranteed
timely delivery of specific application data to a particular destination. In
contrast, standard IP-based networks are designed to provide best effort data
delivery service. Best effort service implies that the network delivers the data
in a timely fashion, although there is no guarantee. During times of
congestion, packets may be delayed, sent sporadically, or dropped. For typical
Internet applications, such as electronic mail and file transfer, a slight
degradation in service is acceptable and, in many cases, unnoticeable.
Conversely, any degradation of service has undesirable effects on applications
with strict timing requirements, such as voice or multimedia.
QoS is a means of providing consistent, predictable data delivery by
distinguishing between packets that have strict timing requirements from
those that are more tolerant of delay. Packets with strict timing requirements
are given special treatment in a QoS-capable network. To accomplish this, all
elements of the network must be QoS-capable. If one node is unable to meet
the necessary timing requirements, this creates a deficiency in the network
path and the performance of the entire packet flow is compromised.
Access Control Lists
The PowerConnect ACL feature allows classification of packets based upon
Layer 2 through Layer 4 header information. An Ethernet IPv6 packet is
distinguished from an IPv4 packet by its unique Ether-type value; thus, all
IPv4 and IPv6 classifiers include the Ether-type field.
Multiple ACLs per interface are supported. The ACLs can be combination of
Layer 2 and/or Layer 3/4 ACLs.
ACL assignment is appropriate for both physical ports and LAGs.
2CSPC4.XCT-SWUM2XX1.book Page 645 Monday, October 3, 2011 11:05 AM