Selecting Internetworking Devices for a Campus Network Design 341
Selecting Internetworking Devices for a Campus
Network Design
At this point in the network design process, you have developed a network topology and
should have an idea of which segments will be shared with hubs or repeaters, bridged with
bridges or switches, or routed using routers. Table 10-6 provides a review of the major
differences between hubs (repeaters), bridges, switches, and routers.
After you have designed a network topology and made some decisions regarding the
placement and scope of shared, switched, and routed network segments, you should then
recommend actual hubs, switches, bridges, and routers from various vendors. This section
covers selection criteria you can use when making decisions.
Criteria for selecting internetworking devices in general include the following:
The number of ports
Processing speed
The amount of memory
The amount of latency introduced when the device relays data
Table 10-6 Comparing Hubs, Bridges, Switches, and Routers
OSI Layers
Implemented
How Bandwidth
Domains Are
Segmented
How Broadcast
Domains Are
Segmented
Typical
Deployment
Typical Additional
Features
Hub 1 All ports are in the
same bandwidth
domain.
All ports are in the
same broadcast
domain.
Connects indi-
vidual devices
in small LANs
Autopartitioning to
isolate misbehaving
nodes
Bridge 1–2 Each port delineates
a bandwidth
domain.
All ports are in the
same broadcast
domain.
Connects
networks
User-configured
packet filtering
Switch 1–2 Each port delineates
a bandwidth
domain.
All ports are in the
same broadcast
domain.
Connects indi-
vidual devices
or networks
Filtering, ATM
capabilities, cut-
through processing,
multimedia (multicast)
features
Router 1–3 Each port delineates
a bandwidth
domain.
Each port
delineates a
broadcast domain.
Connects
networks
Filtering, firewalling,
high-speed WAN
links, compression,
advanced queuing and
forwarding processes,
multimedia (multicast)
features
342 Chapter 10: Selecting Technologies and Devices for Campus Networks
Throughput in packets per second (or cells per second for ATM)
LAN and WAN technologies supported
Autosensing of speed (for example, 10 or 100 Mbps)
Autodetection of half- versus full-duplex operation
Media (cabling) supported
Ease of configuration
Manageability (for example, support for Simple Network Management Protocol
[SNMP] and remote monitoring [RMON], status indicators)
Cost
Mean time between failure (MTBF) and mean time to repair (MTTR)
Support for packet filters and other security measures
Support for hot-swappable components
Support for redundant power supplies
Support for QoS features
Availability and quality of technical support
Availability and quality of documentation
Availability and quality of training (for complex switches and routers)
Reputation and viability of the vendor
Availability of independent test results that confirm the performance of the device
For switches and bridges (including wireless bridges), the following criteria can be added
to the first bulleted list in this section:
Bridging technologies supported (transparent bridging, spanning-tree algorithm,
remote bridging, and so on)
Advanced spanning-tree features supported (rapid reconfiguration of spanning trees
[802.1w] and multiple spanning trees [802.1s])
The number of MAC addresses that the switch or bridge can learn
Support for port security (802.1X)
Support for cut-through switching
Support for adaptive cut-through switching
VLAN technologies supported, such as the Virtual Trunking Protocol (VTP), Inter-
Switch Link (ISL) protocol, and IEEE 802.1Q
Support for multicast applications (for example, the ability to participate in the
Internet Group Management Protocol [IGMP] to control the spread of multicast
packets)

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