Information Technology Reference
In-Depth Information
Examples of data-link layer technologies are the following:
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Frame Relay
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Asynchronous Transport Mode (ATM)
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Synchronous Data Link Control (SDLC)
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High-level data-link control (HDLC)
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IEEE 802.3z and IEEE 802.3ab (Gigabit Ethernet)
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IEEE 802.3u (Fast Ethernet)
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Ethernet version 2
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Integrated Services Digital Network (ISDN)
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Point-to-Point Protocol (PPP)
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Token Ring
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Spanning-Tree Protocol (STP)
Network Layer (OSI Layer 3)
The network layer is concerned with the routing of information and methods to determine paths
to a destination. Information at this layer is called packets. Specifications include routing
protocols, logical network addressing, and packet fragmentation. Routers operate in this layer.
The CCIE lives and dies in this layer.
Examples of network layer specifications are the following:
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Internet Protocol (IP)
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Routing Information Protocol (RIP)
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Open Shortest Path First (OSPF)
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Enhanced Interior Gateway Routing Protocol (EIGRP)
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Internetwork Packet Exchange (IPX)
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Connectionless Network Protocol (CLNP)
Transport Layer (OSI Layer 4)
The transport layer provides reliable, transparent transport of data segments from upper layers.
It provides end-to-end error checking and recovery, multiplexing, virtual circuit management,
and flow control. Messages are assigned a sequence number at the transmission end. At the
receiving end the packets are reassembled, checked for errors, and acknowledged. Flow control
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