© 2007 Cisco Systems, Inc. All rights reserved.Cisco Public ITE PC v4.0 Chapter 1 1 OSI Data Link Layer Network Fundamentals – Chapter 7.

ITE PC v4.0 Chapter 1 2 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Objectives 1.Data Link Layer – Accessing the Media. 2.Data Link Sublayers. (LLC-MAC) 3.Framing. (different framing protocols) 4.Media access control 5.NIC 6.Layer 2 devices 7.Data link layer standards

ITE PC v4.0 Chapter 1 5 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Layer 2 Frame Data link sub-layers : LLC : (logical link control) interact with network layer protocol MAC : (media access control) provide physical addressing and other data link layer functions Note: LLC sub-layer frame (IEEE 802.2) is encapsulated into MAC sub-layer frame (IEEE 802.3) IEEE version ( IEEE 802.3 (MAC sub-layer) “Interact with physical layer” + IEEE 802.2 (LLC sub-layer) “Interact with Internet layer” ) Physical Layer IEEE 802.2 Logical Link Control sub-layer IEEE 802.3 Media Access Control sub-layer IEEE 802.3 Physical Layer Data-Link Layer Ethernet II

ITE PC v4.0 Chapter 1 6 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Data Link Sublayers  Logical Link Control (LLC) places information in the frame that identifies which Network layer protocol is being used for the frame.  Media Access Control (MAC) provides Data Link layer addressing and delimiting of data according to the type of Data Link layer protocol in use.  Separating the Data Link layer into sublayers allows for one type of frame defined by the upper layer to access different types of media defined by the lower layer.

ITE PC v4.0 Chapter 1 11 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 7.2.1 Placing data on the media  Regulating the placement of data frames onto the media is known as media access control.

ITE PC v4.0 Chapter 1 13 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 7.2.3 Media access control for non-shared media  Define Full Duplex and Half Duplex as it relates to Media Access Control for non-shared media

ITE PC v4.0 Chapter 1 14 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 7.3.3 Addressing- Where the frame goes  Describe the role of addressing in the Data Link layer and identify cases where addresses are needed and cases where addresses are not needed

ITE PC v4.0 Chapter 1 15 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 7.1.4 Connecting upper layer services to the media  Describe the role the Data Link layer plays in linking the software and hardware layers

ITE PC v4.0 Chapter 1 16 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public NIC  the Data Link layer is embodied as a physical entity, such as an Ethernet network interface card (NIC), which inserts into the system bus of a computer and makes the connection between running software processes on the computer and physical media.  The NIC is not solely a physical entity, however. Software associated with the NIC enables the NIC to perform its intermediary functions of preparing data for transmission and encoding the data as signals to be sent on the associated media.

ITE PC v4.0 Chapter 1 17 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Layer 2 devices A layer 2 device is a device that understand MAC, for example: NIC (Network Interface Card) Bridge : - address learning - forwarding decisions are based on software - bridge is used for LAN segmentation - max. 16 port. Switch: - a multi-port bridge up to 567 port - forwarding decisions are based on hardware ASIC (faster than bridge)

ITE PC v4.0 Chapter 1 19 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Summary 1.Data Link Layer – Accessing the Media. 2.Data Link Sublayers. (LLC-MAC) 3.Framing. (different framing protocols) 4.Media access control 5.NIC 6.Layer 2 devices 7.Data link layer standards

ITE PC v4.0 Chapter 1 21 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 8.1.3 Physical Layer - Standards  Distinguish who establishes and maintains standards for the Physical layers compared to those for the other layers of the network

ITE PC v4.0 Chapter 1 22 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 8.1.1 Physical layer purpose.  Describe the role of bits in representing a frame as it is transported across the local media.

ITE PC v4.0 Chapter 1 23 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 8.1.4 Physical Layer Fundamental Principles  The three fundamental functions of the Physical layer are: –The physical components –Data encoding –Signaling  The physical elements are the electronic hardware devices, media and connectors that transmit and carry the signals to represent the bits.

ITE PC v4.0 Chapter 1 25 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 8.3.1 Types of physical media.  standards for copper media are defined for the: –Type of copper cabling used –Bandwidth of the communication –Type of connectors used –Pinout and color codes of connections to the media –Maximum distance of the media

ITE PC v4.0 Chapter 1 26 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Coaxial Cable  Coaxial cable consists of a hollow outer cylindrical conductor that surrounds a single inner wire made of two conducting elements.  One of these elements, located in the center of the cable, is a copper conductor.  Surrounding the copper conductor is a layer of flexible insulation.  Over this insulating material is a woven copper braid or metallic foil that acts as the second wire in the circuit and as a shield for the inner conductor. 3.1.7

ITE PC v4.0 Chapter 1 28 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Coaxial Cable  For LANs, coaxial cable offers several advantages. It can be run longer distances than shielded twisted pair, STP, and unshielded twisted pair, UTP, cable without the need for repeaters. Coaxial cable is less expensive than fiber-optic cable, and the technology is well known. 3.1.7

ITE PC v4.0 Chapter 1 29 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Shielded Twisted-Pair  Shielded twisted-pair cable (STP) combines the techniques of shielding, cancellation, and twisting of wires.  Each pair of wires is wrapped in metallic foil.  The four pairs of wires are wrapped in an overall metallic braid or foil.  STP affords greater protection from all types of external interference, but is more expensive and difficult to install than UTP.  The metallic shielding materials in STP need to be grounded at both ends. 3.1.8

ITE PC v4.0 Chapter 1 30 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Unshielded Twisted-Pair  Unshielded twisted-pair cable (UTP) is a four-pair wire medium used in a variety of networks.  Each of the 8 individual copper wires in the UTP cable is covered by insulating material.  In addition, each pair of wires is twisted around each other.  This type of cable relies solely on the cancellation effect produced by the twisted wire pairs, to limit signal degradation caused by EMI and RFI.  CAT 5 is the one most frequently recommended and implemented in installations today. 3.1.9

ITE PC v4.0 Chapter 1 31 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Unshielded Twisted-Pair  Unshielded twisted-pair cable has many advantages. It is easy to install and is less expensive than other types of networking media.  However, the real advantage is the size. Since it has such a small external diameter, UTP does not fill up wiring ducts as rapidly as other types of cable. 3.1.9

ITE PC v4.0 Chapter 1 34 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Optical Media  The part of an optical fiber through which light rays travel is called the core of the fiber.  If the diameter of the core of the fiber is large enough so that there are many paths that light can take through the fiber, the fiber is called “multimode” fiber.  Single-mode fiber has a much smaller core that only allows light rays to travel along one mode inside the fiber. 3.2.6

ITE PC v4.0 Chapter 1 35 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Optical Media  Every fiber-optic cable used for networking consists of two glass fibers encased in separate sheaths.  One fiber carries transmitted data from device A to device B.  The second fiber carries data from device B to device A.  This provides a full-duplex communication link. 3.2.6

ITE PC v4.0 Chapter 1 37 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 8.3.7 Wireless media.  Describe the role of radio waves when using air as the media and the increased need for security in wireless communications

ITE PC v4.0 Chapter 1 40 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Signaling and Encoding  The Physical layer must generate the electrical, optical, or wireless signals that represent the "1" and "0" on the media. The method of representing the bits is called the signaling method.  Encoding is a method of converting a stream of data bits into a predefined code.

ITE PC v4.0 Chapter 1 42 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 8.2.2 Encoding.  Advantages using code groups include: 1.Reducing bit level error (more transitions) 2.Limiting the effective energy transmitted into the media (DC balancing. ) 3.Helping to distinguish data bits from control bits 4.Better media error detection (invalid symbols)

ITE PC v4.0 Chapter 1 43 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 8.2.1 Signaling bits for the media.  The Physical layer represents each of the bits in the frame as a signal  Bits are represented on the medium by changing one or more of the following characteristics of a signal: –Amplitude –Frequency –Phase

ITE PC v4.0 Chapter 1 44 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 8.2.1 Signaling bits for the media.  Explain that network communication at this layer consists of individual bits encoded onto the Physical layer and describe the basic encoding techniques.

© 2007 Cisco Systems, Inc. All rights reserved.Cisco Public ITE PC v4.0 Chapter 1 1 OSI Data Link Layer Network Fundamentals – Chapter 7.

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© 2007 Cisco Systems, Inc. All rights reserved.Cisco Public ITE PC v4.0 Chapter 1 1 OSI Data Link Layer Network Fundamentals – Chapter 7.

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Presentation on theme: "© 2007 Cisco Systems, Inc. All rights reserved.Cisco Public ITE PC v4.0 Chapter 1 1 OSI Data Link Layer Network Fundamentals – Chapter 7."— Presentation transcript:

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