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Wired LANs:
Ethernet - Coggle Diagram
Wired LANs:
Ethernet
ETHERNET PROTOCOL
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Ethernet Evolution
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four generations: Standard Ethernet (10 Mbps), Fast Ethernet (100 Mbps), Gigabit Ethernet (1 Gbps), and 10 Gigabit Ethernet (10 Gbps), as shown in Figure 13.2.
STANDARD ETHERNET
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Characteristics
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Ethernet provides a connectionless service, which means each frame sent is independent of the previous or next frame.
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The sender may overwhelm the receiver with frames, which may result in dropping frames.
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If a frame drops, the sender will not know about it.
Addressing
The NIC fits inside the station and provides the station with a link-layer address. The Ethernet address is 6 bytes (48 bits), normally written in hexadecimal notation, with a colon between the bytes.
Each station on an Ethernet network (such as a PC, workstation, or printer) has its own network interface card (NIC).
Unicast, Multicast, and Broadcast Addresses
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If the least significant bit of the first byte in a destination address is 0, the address is unicast; otherwise, it is multicast.
The destination address, however, can be unicast, multicast, or broadcast.
Note that with the way the bits are transmitted, the unicast/multicast bit is the first bit which is transmitted or received.
The broadcast address is a special case of the multicast address: the recipients are all the stations on the LAN. A broadcast destination address is forty-eight 1s.
Standard Ethernet uses a coaxial cable (bus topology) or a set of twisted-pair cables with a hub (star topology)
We need to know that transmission in the standard Ethernet is always broadcast, no matter if the intention is unicast, multicast, or broadcast.
In the bus topology, when station A sends a frame to station B, all stations will receive it.
In fact, it floods the network with the frame.
In the star topology, when station A sends a frame to station B, the hub will receive it. Since the hub is a passive element, it does not check the destination address of the frame; it regenerates the bits (if they have been weakened) and sends them to all stations except station A.
how the actual unicast, multicast, and broadcast transmissions are distinguished from each other. The answer is in the way the frames are kept or dropped.
In a unicast transmission, all stations will receive the frame, the intended recipient keeps and handles the frame; the rest discard it.
In a multicast transmission, all stations will receive the frame, the stations that are members of the group keep and handle it; the rest discard it.
In a broadcast transmission, all stations (except the sender) will receive the frame and all stations (except the sender) keep and handle it.
FAST ETHERNET
The designers of the Fast Ethernet needed to make it compatible with the Standard Ethernet. The MAC sublayer was left unchanged.
But the features of the Standard Ethernet that depend on the transmission rate, had to be changed
In the 1990s, Ethernet made a big jump by increasing the transmission rate to 100 Mbps, and the new generation was called the Fast Ethernet.
The goals of Fast Ethernet can be summarized as follows:
-Upgrade the data rate to 100 Mbps.
-Make it compatible with Standard Ethernet.
-Keep the same 48-bit address.
-Keep the same frame format
To be able to handle a 100 Mbps data rate, several changes need to be made at the physical layer.
GIGABIT ETHERNET
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The goals of the Gigabit Ethernet were to upgrade the data rate to 1 Gbps, but keep the address length, the frame format, and the maximum and minimum frame length the same.
The need for an even higher data rate resulted in the design of the Gigabit Ethernet Protocol (1000 Mbps).
10 GIGABIT ETHERNET
In recent years, there has been another look into the Ethernet for use in metropolitan areas
to extend the technology, the data rate, and the coverage distance so that the Ethernet can be used as LAN and MAN (metropolitan area network).
The IEEE committee created 10 Gigabit Ethernet and called it Standard 802.3ae. This data rate is possible only with fiber-optic technology at this time.