Paradyne BitStorm 2400, User Manual

Page: 15 / 90

1. BitStorm 2400 Overview
2400-A2-GB20-10 December 2002
1-5
Layer 2 CoS Support
Traffic management allows for the proactive management of bandwidth allocation.
By provisioning bandwidth management policies, classifying traffic, and applying
traffic shaping, users receive smooth and predictable service.
The integrated Layer 2+ has the ability to recognize flows based on Layer 2 packet
information including:
!
IEEE 802.1p priority information in tagged frames
!
Source MAC Address
!
Destination MAC Address
!
IEEE 802.1Q VLAN identifiers
Additional traffic management features and IP QoS functions will be added in
future releases.
Priority Queuing Support
The BitStorm 2400 and StormPort CPE modems are enabled to recognize and
respond to IEEE 802.1D priority classifications. This standard is also known as the
IEEE 802.1p, which is a subsection of the IEEE 802.1D standard. The 802.1p
priority bits information is carried in a 3-bit field in the IEEE 802.1Q tag.
The CO and CPE modems inspect and classify packets based on the IEEE 802.1p
priority field value. IEEE 802.1p defines 8 levels of priority (0-lowest to 7-highest).
The CO and CPE modems map these priority levels to one of two output queues
(high and low). The Ethernet Ports map these priorities to one of four output
queues (lowest, low, high, highest). This mapping complies with the recommended
mapping in the IEEE 802.1D-1998 standard. The mapping is configurable and may
be set to meet specific implementation standards.
Once traffic has been allocated to the output queues of the CO and CPE modems,
they will be serviced according to strict priority (picked from high until empty). Note
that this process is observed for packets in the downstream direction from the CO
and the upstream direction for the CPE (EtherLoop is a point-to-point connection
that preserves packet order so priority output queuing processes do not have to be
re-run on the receiving device).
Switching Fabric
The Ethernet Switching fabric in the BitStorm 2400 recognizes and responds to
IEEE 802.1D priority classifications. This standard is also known as the IEEE
802.1p which is a subsection of the 802.1D standard. The 802.1p is carried in a
3-bit field in the IEEE 802.1Q tag. The BitStorm 2400 classifies frames based on
the presence and code points (values) of priority information in the IEEE 802.1Q
tag.