Specifications

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DESIGN GUIDE - Data Center LAN Connectivity Design Guide
Not only do these alternatives costs less than Fibre Channel, but they provide higher performance and are easier to
manage. Additionally, separate QoS queues can be used to ensure critical data flows are prioritized appropriately.
For example, a data base application should be prioritized over other less important data flows such as archived
document data. Storage must also be backed up on a regular basis without impacting LAN performance and be
accounted for in the disaster recovery plan.
Quality of Service (QoS)
Each application on the LAN has different QoS requirements. Unified Communications have real-time requirements
that are not necessary for most data applications. VoIP packets, for example, must be efficiently transported
throughout the LAN and WAN to ensure high-quality voice communications, even when the network is experiencing
high utilization or congestion. Simply adding more bandwidth doesn’t make the network voice-friendly. Latency, jitter
and packet loss are common VoIP challenges that must be addressed with QoS queuing and scheduling to ensure
toll-quality VoIP communications.
Traditional applications such as Web browsing and e-mail work fine with the best-effort delivery standard on IP
networks. However, additional requirements must be met to ensure effective delivery of voice, video conferencing
and other real-time applications. Unlike streaming video, for example, real-time voice data can’t be cached nor
can lost voice packets be retransmitted, since both would add an unacceptable delay and ruin the quality of the
communication and result in a poor experience. Voice packets, therefore, must be given top priority when creating
QoS policies.
To facilitate QoS, data can be classified by a combination of physical port, device and protocol. For example, a block of
IP phones connected to a specific LAN segment could be placed in a VLAN designated for voice traffic based on their
port numbers. Or Link Layer Detection Protocol-Media Endpoint (LLDP-MED) may be used to discover an IP phone
and automatically place it on a VLAN using IEEE 802.1X access control. Or traffic from a soft phone can be analyzed
at the protocol level, with voice data given top priority regardless of the source port. Once the data is classified with
the appropriate Differentiated Services Code Point (DSCP), it needs to be queued and scheduled. Most importantly,
the same QoS rules need to be enforced consistently throughout the LAN and WAN.
QoS or Class of Service (CoS) features are built into all Juniper infrastructure, security and application acceleration
solutions. JUNOS Software comes standard with a full complement of QoS services; for example, all EX Series
Ethernet Switches support eight QoS queues per port and offer a range of policing options from best-effort delivery
to enhanced delivery to assured delivery. Since the same JUNOS Software runs all Juniper router and switch
products, the same QoS policies can be implemented throughout the data center LAN and across the WAN for easy
and consistent traffic management. In addition, ASICs in all Juniper routers and switches support QoS by processing
prioritized data and minimizing CPU load.
Data Center Access Layer Design Recommendations
To meet the access requirements of any sized data center, Juniper provides a scalable chassis or a traditional
chassis-based solution.
Scalable Configuration with Virtual Chassis Technology
A data center LAN must be able to accommodate growth and adapt to new technologies. This needs to be done
economically with respect to capital expense, network overhead and network operational expense perspectives.
Juniper Networks addresses these requirements with a true innovation: the EX4200 Ethernet Switches with Virtual
Chassis technology. This innovation advances the economics of networking by delivering the HA and high port
densities of a modular chassis in a compact, cost-effective, pay-as-you-grow platform.
Features and Benefits1.
Each compact EX4200 Series switch offers either 24 100BASE-FX/1000BASE-X ports, 24 10/100/1000BASE-T
ports or 48 10/100/1000BASE-T ports. The 10/100/1000BASE-T platforms offer either full or partial PoE options.
Switches with the partial PoE option provide PoE on the first eight ports of the switch while switches with the
full PoE option provide PoE on all ports. Each PoE port delivers up to 15.4 watts of power and is compatible
with class 0-3 IP phones. The EX4200 Series switches’ built in Link Layer Discovery Protocol-Media Endpoint
Discovery (LLDEP-MED) services provide a standards based mechanism to automate and extend the power
management of these PoE endpoints as well as assist with inventory management and directories. The switches
with the partial PoE option are ideal for data center access deployments where PoE for a small number of IP
phones, WLAN access points or other devices needing power and purchasing full PoE is overkill.