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Animation 3_1
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Bits can be encoded by using electricity. For example, a negative
voltage can be used to represent a 1 and a positive voltage can be
used to represent a 0. The sending device can put a voltage on a wire
for a short time to transmit a bit to the receiving device.
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Animation 5_1
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Computers use multiplexors and demultiplexors to share a single
communication link; the multiplexor chooses one computer to
send data on the communication link and the demultiplexor
routes the data from the link to the destination computer.
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Animation 5_2
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The sender can use the ASCII soh and eotto delimit a
frame. The soh and eot characters are not part of
the transmitted data and only appear on the wire between the sender
and receiver.
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Animation 5_3
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To transmit soh as data, the sender uses byte-stuffing. In
this example, the sender first sends an esc character before
sending soh as data.
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Animation 6_1
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Ethernet is a broadcast LAN technology; a computer transmits data
by sending the data across the entire Ethernet and the data is
received by every NIC attached to the network; only the NIC whose
address appears in the destination field of the Ethernet frame
delivers the frame to the attached computer; the other NICs
discard the frame.
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Animation 6_2
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Ethernet technology employs Carrier Sense Multiple Access/Collision
Detection to arbitrate the use of the single Ethernet cable among
computers attached to the network; each computer waits until the
Ethernet is available (as indicated by the absence of the
carrier) before transmitting data.
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Animation 6_3
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Token ring is a broadcast technology using ring topology; the
each computer passes bits from its upstream neighbor to its
downstream neighbor and make a local copy if its is the
recipient of the frame; the token is used to arbitrate use of
the ring among the computers attached to the network.
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Animation 6_4
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After transmitting a frame, the sender passes the token to the next
station. After receiving the token, the next station can transmit a
frame.
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Animation 6_5
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If two frames are sent simultaneously on an Ethernet, they are said to
sollide. When the transmitting computers sense the
collision, they immediately stop transmitting and retrnasmit the frame
later.
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Animation 9_1
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Repeaters interconnect Ethernet segments by amplifying and retransmitting
signals from one segment to another; the resulting network of segments
is indistinguishable from a single large Ethernet as exactly the
same electrical signals appear on every segment.
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Animation 9_2
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Bridges interconnect Ethernet segments by receiving and retransmitting
entire frames, employing CSMA/CD technology to avoid collisions and
avoiding the propagation of collisions between segments; filtering
bridges can reduce traffic by only forwarding frames on the
path from the source to the destination.
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Animation 9_3
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Routers interconnect Ethernet segments by receiving and retransmitting
IP datagrams carried in hardware frames; routers can limit the scope
of hardware broadcasts and can interconnect network segments that
use dissimilar hardware technologies.
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Animation 10_1
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Packet switches can be linked together into a Wide Area Network. Data
packets delivered to one switch are forwarded through other switches
to the destination.
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Animation 15_1
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A host uses ARP to determine the hardware address of the destination
of an IP datagram. The sender broadcasts an ARP request, the
destination responds with an ARP reply and the sender sends the IP
datagram directly to the destination.
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Animation 16_1
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Hosts and routers consult routing tables to forward IP datagrams.
Each host or router looks in its routing table to determine the next
hop to the destination. If the routing tables are changed, IP
datagrams will follow different paths to the destination.
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Animation 16_2
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This animation converts between 32-bit hexadecimal numbers and the
fields in an IP datagram header.
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Animation 17_1
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In an internet, the protocol software on the source computer constructs
an IP datagram and transmits it to a router
by encapsulating the datagram in a hardware frame. The router
extracts the datagram and retransmits it in a new hardware frame
to the next router on the path to the destination; the destination
extracts the original datagram from the last hardware frame and
delivers the data to the application.
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Animation 20_1
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TCP specifies a three-way handshake to establish a TCP connection
between two computers; the initiating computer send a segment
with the SYN bit sent; the receiving computer responds with a
segment with the SYN and ACK bits sent; the initiating computer
then completes the handshake with a segment with the ACK bit set.
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Animation 20_2
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TCP specifies a three-way handshake to terminate a TCP connection;
the computer initiating the termination sends a segment with
the FIN bit sent, the computer at the other end of the connection
responds with a segment with the FIN and ACK bits set; the initiating
computer then completes the termination handshake with a segment
with the ACK bit set.
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Animation 20_3
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TCP uses sliding window flow control. The receiver defines the
window, and the sender can transmit any of the data in the window.
When the sender receives an acknowledgment, the window moves ahead to
include new, unsent data.
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Animation 20_4
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By changing the size of the window, the receiver can control the rate
at which data are sent.
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Animation 20_5
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If a segment is lost, the window does not advance until the segment is
retransmitted and the sender receives the acknowledgment for the segment.
When the receiver gets a segment out of order, it can send an
acknowledgment for the highest received data byte without sending
individual acknowledgments for the intermediate data.
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Animation 27_1
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