Physical and Data Link Layers Chapter 2 Connecting People To Information
Upon completion of this chapter, you will be able to perform the following tasks: Identify and describe the data link sublayers and their functions Explain the use of MAC addresses Describe the topology and functionality of LANs Differentiate between LAN and WAN protocols Objectives
Connecting People To Information Physical and Data-Link Standards Separate physical and data link layers for LAN and WAN Physical (bits, signals, clocking) Data Link (frames)
Connecting People To Information Physical and Data-Link Standards Separate physical and data link layers for LAN and WAN Physical (bits, signals, clocking) LAN Data Link (frames) EthernetEthernet FDDIFDDI LLC
Connecting People To Information Physical and Data-Link Standards Separate physical and data link layers for LAN and WAN Physical (bits, signals, clocking) LAN WAN Data Link (frames) EthernetEthernet FDDIFDDI LLC X.25 Link Frame Relay ISDN PPP EIA-530 V.35 Dial on Demand SDLC HDLC V.24 HSSI G.703 EIA/TIA-232 EIA/TIA-449
Connecting People To Information LAN Data Link Sublayers LLC refers upward to higher-layer software functions MAC refers downward to lower-layer hardware functions Media Access Control Logical Link ControlNetworkNetwork Data Link Physical LLCLLC MAC
Connecting People To Information LAN Data Link Sublayers LLC refers upward to higher-layer software functions MAC refers downward to lower-layer hardware functions Media Access Control Logical Link Control NetworkNetwork Data Link Physical LLCLLC MAC Frame LLC MAC Packet or Datagram
Connecting People To Information LLC Sublayer Functions Enable upper layers to gain independence over LAN media access Allow service access points (SAPs) from interface sublayers to upper-layer functions
Connecting People To Information Physical and Logical Addressing c
Connecting People To Information MAC Address MAC address is burned into ROM on a network interface card 24 bits c Vendor Code Serial Number ROM RAM
Connecting People To Information Finding the MAC Address Host YHost Z Query Response Example 1: Destination local Router A Example 2: Destination not local Host Z Broadcast Host Z MAC ? Host Z MAC ? Host Z Host Y MAC Host Y MAC Host Z MAC Host Z MAC Host Y Query Broadcast Host Z MAC ? Host Z MAC ? Host Z Response Host Y MAC Host Y MAC Router A MAC Router A MAC Routing Table: Net for Host Z Routing Table: Net for Host Z
Connecting People To Information Written Exercise: Determining MAC Addresses Host A c Host B c Host D c Router C c Router C c Network Y Network X
Common LAN Technologies
Connecting People To Information Ethernet Token Ring FDDI LAN Technology Overview FDDI Dual Ring
Connecting People To Information Ethernet and IEEE Several framing variations exist for this common LAN technology
Connecting People To Information Physical Layer: Ethernet/802.3 Host 10BaseT—Twisted Pair 10Base2—Thin Ethernet 10Base5—Thick Ethernet PC Mac SunHost Hub MAC
Connecting People To Information The Ethernet/802.3 Interface Cisco router’s data link to Ethernet/802.3 uses an interface named E plus a number (for example, E0) a c12. 7c4d E0 E c.34d c12. 83e2
Connecting People To Information Ethernet/802.3 Operation ABCD D B and C Application Presentation Session Transport Network Data Link Physical Application Presentation Session Transport Network Data Link Physical
Connecting People To Information Ethernet/802.3 Broadcast DCBA Application Presentation Session Transport Network Data Link Physical Application Presentation Session Transport Network Data Link Physical Application Presentation Session Transport Network Data Link Physical Application Presentation Session Transport Network Data Link Physical
Connecting People To Information Ethernet Frame Variations Ethernet Frame Frame Preamble DA SA Type Data FCS Preamble DA SA Length Header and Data Header and Data FCS 86624
Connecting People To Information DSAP SSAP CTRL AA CTRL OUI Ether Type Ether Type Upper Layer Data IP, AppleTalk Upper Layer Data IP, AppleTalk DATA Ethernet Frame Variations Frame Preamble DA SA Length Header and Data Header and Data FCS Frame SNAP Frame
Connecting People To Information Ethernet/802.3 Reliability ABCD Collision ABCD JAMJAMJAMJAMJAMJAMJAMJAMJAMJAMJAMJAM
Connecting People To Information High-Speed Ethernet Options 100BaseFX 100BaseT4 100BaseTX 100VG-AnyLAN
Common WAN Technologies
Connecting People To Information WAN Technology Overview SDLC HDLC LAPB PPP X.25 Frame Relay ISDN
Connecting People To Information Physical Layer: WAN (Modem) Data Terminal Equipment End of the user’s device on the WAN link DTE Data Circuit-Terminating Equipment End of the WAN provider’s side of the communication facility DCE EIA/TIA-232 V.35 X.21 HSSI Others CSU/DSU
Connecting People To Information Data Link Layer: WAN Protocols SDLC—Synchronous Data Link Control HDLC—High-Level Data Link Control LAPB—Link Access Procedure, Balanced Frame Relay—Simplified version of HDLC framing PPP—Point-to-Point Protocol X.25—Packet level protocol (PLP) ISDN—Integrated Services Digital Network (data-link signaling) (Modem) CSU/DSU (Modem)