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Group Members. Muhammad Nisar (1421-112085) Muhammad Raza (1421-211007) Tayyab Orangezaib (1421-311067). Data Link Protocol. Synchronous protocol Character-Oriented protocol Bit-Oriented protocol Binary synchronous message block. Data Link Protocol.
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Group Members • Muhammad Nisar (1421-112085) • Muhammad Raza (1421-211007) • Tayyab Orangezaib (1421-311067)
Data Link Protocol • Synchronous protocol • Character-Oriented protocol • Bit-Oriented protocol • Binary synchronous message block
Data Link Protocol Data Link Protocol~ is a set of specifications used to implementation the data link layer
Synchronous protocol Synchronous protocol involve sending timing information along with data bytes, so the receiver can remain in synchronization with the sender. ~ for LAN, MAN, WAN
Synchronous protocol(cont’d) • character-oriented protocol ~ frame or packet is interpreted as a series of characters • bit-oriented protocol ~ frame of packet is interpreted as a series of bits
Character-Oriented protocol ~ are not as efficient as bit-oriented protocols and therefore one now seldom used Special character for start and end of message • popular protocol : BSC(Binary synchronous communication)
Character-Oriented protocol(cont’d) • BSC(Binary Synchronous Communication) • Developed in 1964 • usable in both point-to-point and multipoint configuration • support half-duplex transmission • do not support full-duplex transmission
Character-Oriented protocol(cont’d) • Control character for BSC Character ASCII Code Function Good even frame received or ready to receive Good odd frame received Data transparency maker Request for a response Sender terminating End of transmission block; ACK required End of text in a message End of intermediate block in a multiblock transmission Bad frame received nothing to send Filler character Urgent message from receiver Header information beings Text beings Alerts receiver to incoming frame Sender is pausing but not relinquishing the line Good frame received but not ready to receive more ACK 0 ACK 1 DLE ENQ EOT ETB ETX ITB NAK NUL RVI SOH STX SYN TTD WACK DLE and 0 DLE and 1 DLE ENQ EOT ETB ETX US NAK NULL DLE and < SOH STX SYN STX and ENQ DLE and ;
Bit-Oriented protocol ~ can pack more information into shorter frames and avoid the transparency problem of character-oriented protocol Use flag character for start and end of message
Bit-Oriented protocol(cont’d) Division of bit-oriented protocol
Bit-Oriented protocol(cont’d) • SDLC(Synchronous Data Link Control) ~ developed in 1975 • HDLC(High-Level Data Link Control) ~ developed by ISO in 1979 • LAPs(Link Access Procedures)LAPB, LAPD, LAPM etc ~ developed by since 1981 • PPP (Point-to-point Protocol) frame relay ~ developed by ANSI in 1990
Binary Synchronous Message Blocks • Messages are sent in blocks. Message blocks have the following format
Binary Synchronous Message Blocks • Each message block can contain up to three parts, • an optional header • the text • a trailer
Binary Synchronous Message Blocks • The control characters used to identify these parts are, • SOH (Start of header) indicates the header follows • STX (Start of text) indicates the text follows • ETX (End of text or text length) indicates the end of the text block
Binary Synchronous Message Blocks • Block check character (BCC) • Synchronization character (SYN) • Text