Specifications

Copyright © 2009, Juniper Networks, Inc. 9
DESIGN GUIDE - Data Center LAN Connectivity Design Guide
Data Center Network Design Considerations
A new data center LAN design is needed as legacy solutions cannot meet these key requirements, nor reduce costs
and streamline operations. The LAN design must also scale and accommodate emerging computing trends and
additional network services without an entire redesign. The new design should be architected in order to maximize
efficiency gains from technologies like virtualization.
Services Required in the Data Center
The following high-level services are required of data centers to provide carrier-class network service throughout
the enterprise and thus optimize efficient business operations. Each of these areas is addressed in more detail in
this document and, where appropriate, additional considerations or challenges for a specific service, feature or data
center category are presented.
Figure 2: Data center LAN functional design model
High Availability (HA)
With the consolidation and centralization of servers and resources, HA is a key requirement from the data center
LAN. Redundancy of critical subsystems and seamless failover are needed for routers, security appliances, and any
other devices on the user-to-data center path. Designing HA into the data center network requires consideration of
three key aspects — device availability, network availability and operational availability.
Table 1: The Three Aspects of Designing HA Into the Enterprise Network
DEVICE AVAILABILITY NETWORK AVAILABILITY OPERATIONAL AVAILABILITY
• Redundant components
• Hot-swappable components
• Modular operating system
software
• In service software upgrades
• Network access control
• Redundant devices and paths
• Routed network designs
• Quality of service
• Open standards
• Consistent software features
• Automate operational tasks
• Reduce complexity
Network devices deployed within the data center should support device-level HA with components such as redundant
power supplies, fans and route engines. The operating system software running on data center network devices
should have a modular architecture so that software failures will be isolated to a single process and not impact other
critical operating system services, ensuring system and network availability. Features such as in-service software
updates (ISSU) also maintain network availability while still providing network software updates.
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