Specifications

Ethernet Tip – Use 10/100 autosensing hub or switch. This allows a mix of 10 and 100Mbp/s

computers. Internally the hub combines all low-speed ports together and all high-speed ports. If a

packet goes between different speed ports the hub does a store and forward. The packet is

completely assembled at the incoming speed then sent out at the outgoing speed.

7.1.4 Managed vs Unmanaged Hubs and Switches

Ethernet hubs and switches come in both managed or unmanaged versions. Managed devices allow the

administrator to control various parameters and observe traffic. These features are valuable in a corporate

network but are overkill in a home network. Unmanaged devices are considerable less expensive.

7.1.5 Preferred Topology

For maximum flexibility a switch should be used in the wiring closet. This maximizes total network

bandwidth. Using a central switch allows hubs to be used in each room if additional Ethernet drops are

needed. Switches used to be very expensive, but recently switch prices have been dramatically reduced,

making a switch the preferred choice.

7.2 Alternatives to Wired Ethernet

Wired Ethernet is the dominant commercial LAN. It is also popular in new home construction. The cost of

installing network wiring is low if done when the house is being built. The situation is more difficult for

existing homes. The cost and disruption of installing new wiring discourage folks from installing a home

network. Various “no new wire” initiatives attempt to minimize impediments to home networking. These

initiatives operate at lower speed then Wired Ethernet but have the advantage on not requiring dedicated

wiring.

7.2.1 PhoneLine Networking

The Home Phoneline Network Alliance uses phone wiring to create a 1Mbps Ethernet type LAN. This

allows computers to be interconnected wherever a phone jack exists. Recent revision to the specification

increased speed to 10Mbps. The specification allows analog telephone, DSL, and LAN to coexist on a

single pair of ordinary telephone wire.

Home PhoneLine LAN use Ethernet packets with minor changes to the header. The physical layer

hardware adds the unique header information for transmission and removes it on reception. This make

HomePNA look like any other Ethernet LAN to software.

HomePNA equipped computers cannot connect to UTP Ethernet directly, a bridge is needed to rate match

between the two networks and deal with minor signaling difference. Adapters such as the Linksys Network

Bridge can be used to connect a HomePNA LAN to Ethernet. This allows HomePNA and Ethernet devices

to communicate as if they were physically connected to the same LAN.

7.2.2 RF Wireless

Great strides have been made in creating high performance low cost radio LANs. Significant overlap exists

between the three competing RF LAN technologies. For the foreseeable future RF technology is at its best

where mobility is of paramount importance, and bandwidth of lesser importance.

IEEE 802.11 The original version of the spec supported 2Mbp/s, 802.11b runs at 11Mbp/s in the 2.4Ghz

ISM band. 802.11a delivers 54Mbp/s in the 5Ghz band. The WiFi trade association insures

interoperability. 802.11 operate in two modes ad hoc peer-to-peer and managed. Managed mode requires