Nortel BayStack 5520-24T-PWR Specifications page 8

Figure 6. Fail-safe stacking
480 Gbps maximum stacking
bandwidth for the stack
In the unlikely event of a
switch failure, the stack integrity is
maintained: remaining switches
continue to work as a stack.
8
Load sharing
A BayStack 5520-24T-PWR or 5520-48T-PWR Switch provides up to 320 watts available for
Power over Ethernet devices. With the addition of a BayStack 15 PSU chassis and the 600-watt
RPSU module to the BayStack 5520-48T-PWR Switch, up to 740 watts of power can be
supplied to power devices. This solution will provide 15.4 W per port from the BayStack 5520-
48T-PWR Switch. Without the BayStack 15 Power Supply Unit (PSU), the BayStack 5520-
48T-PWR Switch would supply an average of 6.5 W per port (ports can exceed 6.5 W per port
as long as the total of all ports requiring power does not exceed 320 W). With the addition of a
BayStack 15 PSU chassis and the 600-watt RPSU module to the BayStack 5520-24T-PWR
Switch, up to 370 watts of power can be supplied to power devices. This solution will provide
15.4 W per port from the BayStack 5520-24T-PWR Switch. Without BayStack 15 PSU, the
BayStack 5520-24T-PWR Switch would supply an average of 13 W per port (ports can exceed
13 W per port as long as the total of all ports requiring power does not exceed 320 W). A DC
cable connector cable is required to connect from a BayStack 5520 Switch to the BayStack 15
RPSU module (see ordering information section for order numbers).
Redundant power support
With connectivity to the BayStack 15 PSU and RPSU module, a BayStack 5520 Switch
delivers redundant power supply support crucial in mission-critical environments. Nortel
Networks BayStack 15 Power Supply Unit is capable of having up to three 600-watt power
supply modules to provide redundant power supply support to up to three BayStack 5520
Switches. A DC cable connector cable is required to connect from a BayStack 5520 Switch
to a BayStack 15 RPSU module (see ordering information section for order numbers).
Uninterruptible power supply support
For uninterruptible power supply support, a third-party vendor such as APC (www.apc.com)
is recommended to provide UPS support to the BayStack 5520 Switches.
IPv6 filtering and classification support for future applications
BayStack 5520 Switches are able to identify, prioritize, classify, and redirect IPv6 traffic to a
router. These switches can address the need for larger addressing and tighter security as the
networks grow.
Jumbo frame support for larger file applications
Jumbo frame support of up to 9,216 bytes is provided on each port for applications requiring
large frames such as graphics and video applications.
Quality of Service (QoS)
The QoS features of the BayStack 5520 Switch allow users to not only utilize bandwidth
more efficiently, optimizing existing network resources and capabilities, but also provide
packet classification and marking at the edge of the network, simplifying the QoS deploy-
ment at the aggregation and core of the network. By classifying, prioritizing, policing, and
marking LAN traffic (based on DiffServ, Code Point, and 802.1p), networks can offer
reliable connectivity and required bandwidth for mission-critical applications, such as IP
Telephony, to specific groups, users, and individual devices.
For each of these applications, advanced QoS features support Internet Engineering Task
Force (IETF), the standard DiffServ QoS architecture—a packet classification based on the
content of IP packet header fields (voice, video, data)—as well as traffic policing.
QoS and policy management
DiffServ QoS enables networks to read, alter, prioritize, tag, or mark IP packets based upon
information embedded in the Type of Service (ToS) field. The level of service can be marked
in the embedded information inside the ToS field of each IP packet. DiffServ is based on the
ToS field. BayStack 5520 Switches have application-specific integrated circuits (ASICs) to
enable the DiffServ Code Point (DSCP) to be mapped to the IEEE 802.1p user priority bits
to provide consistent QoS at Layer 3 (IP) and Layer 2 (Ethernet). The QoS policies can be
configured via the BayStack 5520 Switch's built-in Web-based management tools to facilitate
QoS. Alternatively, Optivity* Policy Services can be utilized for dynamic end-to-end enterprise-
wide policy and QoS management.