network concepts. networks lan wan main concepts n protocol n media n topology
Post on 21-Dec-2015
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TRANSCRIPT
OSI Layers
• Physical– Signal encoding (voltage, amps, timing)– Connectors (BNC, RJ-45, ST)– Bit oriented
• Data Link– Frame oriented– Error detection– Media access control (token, CSMA/CD)
OSI
• Network– packet (datagram) oriented– Route data from network to network– Fragment and reassemble packets
• Transport– Reliable connection – ACK, NACK– Sequenced delivery– Flow control
OSI Layers
• Session– Logical connections
• Presentation– Character codes (EBCDIC vs. ASCII), encryption,
Compression (nice theory, usually done in other layers)
• Application– Like ftp, telnet, email, www, file and printer sharing
IEEE vs. Ethernet Terminology
Ethernet IEEE 802.3
Station DTE - Data Terminal Equipment
Transceiver cable AUI - Attachment Unit Interface
Transceiver MAU - Medium Attachment Unit
Connector MDI - Medium Dependent Interface
Ethernet Frame
Preamble DestinationAddress
SourceAddress
Length/Type
LLC/Data
FrameCheck Sequence
64 bits of alternating ones and zeroes, for hardware synchronization, ending with twoones
Ethernet Frame
Preamble DestinationAddress
SourceAddress
Length/Type
LLC/Data
FrameCheck Sequence
48-bit address of station frameis being sent to
Ethernet Frame
Preamble DestinationAddress
SourceAddress
Length/Type
LLC/Data
FrameCheck Sequence
48-bit address of stationsending the frame
Ethernet Frame
Preamble DestinationAddress
SourceAddress
Length/Type
LLC/Data
FrameCheck Sequence
16-bit field, length of frame in 802.3, type of frame in DIX
Ethernet Frame
Preamble DestinationAddress
SourceAddress
Length/Type
LLC/Data
FrameCheck Sequence
46 to 1500 bytes of data, includes LLCfields in 802.3
Ethernet Frame
Preamble DestinationAddress
SourceAddress
Length/Type
LLC/Data
FrameCheck Sequence
32-bit cyclic redundancy check (CRC)code
Ethernet Addresses
48 bit normally shown in HEX
e.g.: 02-60-8C-44-59-E0 first 24 bits are obtained from IEEE by hardware manufacturers
one bit is used to distinguish unicast from multicast addresses
one bit is used to distinguish locally assigned addresses(rare) from globally assigned addresses (typical)
Transmission Types
Unicast - intended for one specific station Broadcast - intended for all stations Multicast - intended for a group of stations
CSMA/CD
Carrier Sense, Multiple Access with Collision Detection
Carrier sense - don't transmit if there is already a signal
Collision detection - if a collision is detected stop, wait, and retransmit