Content

| 1.3 |  | Building-Block Approach |
| 1.3.8 |  | Large campus networks |

Large campus networks have redundancy, high bandwidth, and well-defined core, distribution, and access layers. In typical designs, the buildings or different parts of the campus are connected across a high-performance switched backbone. Network redundancy and high availability are provided at each layer and a high capacity centralized server farm provides resources to the campus.

Businesses operating large campus networks area increasingly looking for infrastructure upgrades to:

- Support high-bandwidth applications such as voice, video, and IP multicast
- Support for applications based on Novell IPX, DECnet, AppleTalk, and SNA
- Offer high availability, performance, and manageability for the company’s intranet

Large campus networks use Layer 2, Layer 3, or Asynchronous Transfer Mode (ATM) backbone solutions to expand the network.

Layer 2 Backbone
Layer 2 backbone designs are commonly used when cost-effectiveness and high availability are high priorities. Businesses operating large campus networks are also increasingly looking for infrastructure upgrades to:

- Support high-bandwidth applications based on IP
- Provide high performance and fast recovery from failures
- Support applications based on Novell IPX, DECnet, AppleTalk, and SNA

Campus building blocks and server farms connect to the backbone with redundant Gigabit Ethernet or Gigabit EtherChannel trunks. Layer 3 switching across the backbone uses routing based on EIGRP, OSPF, or IS-IS for load balancing and fast recovery from failures.

Layer 3 Backbone
Layer 3 backbone designs are commonly used when very high performance is desired for supporting multimedia applications based on IP unicast and multicast. Additional requirements of these designs typically include:

- Nonblocking campus backbone that scales to many Gbps of throughput
- Broadcast containment
- Very fast deterministic failure recovery, campus-wide
- Support applications based on Novell IPX, DECnet, AppleTalk, and SNA

This design solution provides a manageable switched infrastructure that scales to a huge campus with many buildings and tens of thousands of networked devices.

Buildings connect to a very high-performance, nonblocking Layer 3 switched backbone. Fast failure recovery is achieved campus-wide using a Layer 3 routing protocol such as EIGRP, OSPF, or IS-IS. One or several high-capacity server farms provide application resources to the campus.

The Layer 3 backbone is ideal for multicast traffic because PIM runs on the Layer 3 switches in the backbone. PIM routes multicasts efficiently to their destinations along a shortest path tree, as opposed to the multicast flooding inherent in a Layer 2 switched backbone design.

ATM Backbone
ATM backbone designs are typically used for a very large switched campus intranet that demands high performance and availability. Requirements of these designs typically include:

- High performance and very high availability for IP applications
- Trunking for native real-time voice and video applications
- Fast deterministic failure recovery for high application availability
- Support applications based on Novell IPX, DECnet, AppleTalk, and SNA

This design solution provides a manageable switched infrastructure for a large campus with thousands of networked devices.

Buildings are connected across a high-performance ATM switched backbone. IP routing protocols as well as ATM routing with Private Network-to-Network Interface (PNNI) provide network redundancy and high availability. One or more high-capacity server farms provide resources to the campus.

Although ATM is still popular in the world of telecommunications, its use as a campus backbone solution appears to be on the decline.