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High speed networks linking an organization's LANs -
Backbone Network Components
Network cable - Functions in the same way as in LANs. Optical fiber - more commonly chosen because it provides higher data rates.
Most switches operate at the data link layer. They connect two or more network segments that use the same data link and network protocol. They may connect the same or different types of cable.
control the movement of packets through the networks
Operate at network layer and use network layer addresses in processing. More complex than switches or routers. Connect two or more networks that use the same or different data link and network protocols. Some …
Other Backbone Network Devices
Terminology in marketplace is variable by vendor. Layer-3 switches - Similar to L2 switches, but switch messages based on network layer addresses (usually IP address). Have the best of both switches and routers. Can sup…
Backbone Network Architectures
Identifies the way backbone interconnects LANs. Manages way packets from one network move through the backbone to other networks. Three layers: 1. Access layer: used in LANs attached to BB. 2. Distribution layer: connects …
Fundamental Backbone Architectures
Switched Backbones: most common type of backbone, used in distribution layer, used in new buildings, sometimes in core layer, can be rack or chassis based.
Replaces the many routers of other designs - Backbone has more cables, but fewer devices.
Rack-Based Switched Backbones
Places all network switch equipment physically in one "rack" room - Easy maintenance and upgrade. Requires more cable, but usually small part of overall cost. Main Distribution Facility (MDF) or Central Distribution Facility (CD…
Chassis-Based Switched Backbones
Use a "chassis" switch instead of a rack - Enables administrators to plug modules into switch.
Move packets using network layer addresses. Commonly used at the core layer - Connecting LANs in different buildings in the campus. Can be used at the distribution layer as well. LANs can use different …
Virtual LANs (VLANs)
A new type of LAN-BN architecture - Made possible by high-speed intelligent switches.
How VLANs Work
Each computer is assigned into a VLAN that has a VLAN ID.
Multiswitch VLAN Operations
Same as single switch VLAN, except uses several switches, perhaps in core between buildings.
VLAN Operating Characteristics
Advantages of VLANs - Faster performance: Allow precise management of traffic flow and ability to allocate resources to different type of applications. Traffic prioritization (via 802.1q VLAN tag): Include in the tag: a priority …
Best Practice Backbone Design
Architectures - At distribution layer -> switched backbone because of performance and cost.
Recommendations for BB Design
Best architecture - Switched backbone or VLAN at distribution layer. Routed backbone at core layer. Best technology - Gigabit Ethernet. Ideal design: A mixture of layer-2 and layer-3 Ethernet switches. Access Layer - 100Base-T L…
Improving Backbone Performance
Improve computer and device performance - Upgrade them to faster devices.Change to a more appropriate routing protocol: Distance vector - typically used on BNs. Link state - typically used on WANs and MANs. Use gig…
Implications for Management
Amount of traffic backbone needs to support is increasing at faster rate - May require that BN be replaced. Design BN to be easily upgradeable. ATM is legacy technology - Vendors stopping the productio…