Ch 7 -  Chapter 7 Data Link Layer
Objectives <ul><li>Explain the  role of Data Link layer  protocols in data transmission  </li></ul><ul><li>Describe how th...
Data Link Layer <ul><li>The Data Link layer  prepares  Network layer packets for  transmission and control  access to the ...
Data Link Layer Terminology <ul><li>The following terms are specific to this layer </li></ul>Ch 7 -
Network Types   <ul><li>Logical network </li></ul><ul><ul><li>defined at the Network layer by the arrangement of the hiera...
Accessing The Media <ul><li>Data Link Layer protocols governs  how to format a frame for use on different medium . </li></...
Media Access <ul><li>Layer 2  protocols specify the encapsulation of a packet into a frame and the techniques for getting ...
Creating a Frame <ul><li>The Data Link layer prepares a packet for transport across the local media by  encapsulating  it ...
Control Information <ul><li>Data Link layer protocols require control information to enable the protocols to function </li...
Frame Structure <ul><li>Framing breaks the stream into decipherable groupings  </li></ul><ul><ul><li>control information i...
Frame Fields <ul><li>Frame  start  and  stop   </li></ul><ul><ul><li>signal the beginning and end limits of a frame  </li>...
Data Link Layer Function <ul><li>The Data Link layer is an interface between the  upper-layer  processes and the  Physical...
*Data Link Sub-layers Ch 7 -
*Data Link Sub-layers (cont’d) <ul><li>Logical Link Control (LLC) </li></ul><ul><ul><li>defines the  software processes  t...
Data Link Layer Standards <ul><li>Data Link layer services and specifications are defined by multiple standards based on a...
Shared Media Access Ch 7 -
Shared Media Access (cont’d) <ul><li>Regulating the  placement of data frames onto the media  is known as media access con...
*Controlled Access <ul><li>Network takes turn, in sequence, to access the medium </li></ul><ul><ul><li>known as scheduled ...
*Contention-Based Access <ul><li>Allows any device to access the medium whenever it has data to send </li></ul><ul><ul><li...
Contention-Based Access (cont’d) <ul><li>Contention-based systems do not scale well under heavy media use </li></ul><ul><u...
*Carrier Sense Multiple Access <ul><li>CSMA/CD </li></ul><ul><ul><li>device monitors the media for the presence of a data ...
Non-shared Media Access <ul><li>Require little or no control before placing frames onto the media </li></ul><ul><li>The me...
Half-duplex Communication <ul><li>Half-duplex  communication means that the devices can both  transmit  and  receive  on t...
Full-duplex Communication <ul><li>Both devices can  transmit  and  receive  on the media  simultaneously   </li></ul><ul><...
Topologies <ul><li>Physical  topology </li></ul><ul><ul><li>an arrangement of the nodes and the physical connections betwe...
*Topologies (cont’d) Ch 7 -
Point-to-Point Topology <ul><li>A point-to-point topology  connects two nodes directly  together </li></ul><ul><li>The med...
Logical Point-to-Point Topology <ul><li>The end nodes communicating in a point-to-point network can be physically connecte...
Multi-Access Topology(Bus Topology) <ul><li>Enables a  number of nodes  to communicate using a  shared media </li></ul><ul...
Ring Topology <ul><li>Each node in turn receives a frame </li></ul><ul><ul><li>the node removes the frame from the ring an...
The Frame <ul><li>No one frame structure meets the needs of all data transportation across all types of media </li></ul><u...
Role of the Header <ul><li>Start Frame  </li></ul><ul><ul><li>the  beginning  of the frame </li></ul></ul><ul><li>Address ...
Physical Address <ul><li>Devices at the Data Link layer are referred to as  physical addresses   </li></ul><ul><li>(MAC Ad...
Addressing Requirements <ul><li>Point-to-point topology with just two interconnected nodes does not require addressing </l...
Role of the Trailer <ul><li>Frame Check Sequence ( FCS ) </li></ul><ul><ul><li>used to determine if errors occurred in tra...
Data Link Protocols <ul><li>The actual Layer 2 protocol used depends on the logical topology of the network and the implem...
Technology <ul><li>LAN technology </li></ul><ul><ul><li>a LAN typically uses a  high-bandwidth  technology that is capable...
Ethernet Protocol <ul><li>Ethernet is a family of LAN networking technologies that are defined in the IEEE802.2 and 802.3 ...
*Ethernet Protocol (cont’d) <ul><li>The Ethernet frame uses the media access control (MAC) address of the node as the Data...
Point-to-Point Protocol (PPP) <ul><li>PPP is a  WAN protocol  used to deliver frames between  two nodes   </li></ul><ul><l...
Point-to-Point Protocol (cont’d) <ul><li>Figure shows the basic fields in a PPP frame </li></ul>Ch 7 -
Wireless Protocol  <ul><li>802.11 is an extension of the IEEE 802 protocol  </li></ul><ul><ul><li>uses the same 802.2 LLC ...
Wireless Protocol (cont’d) <ul><li>Figure shows the fields in an 802.11 frame  </li></ul>Ch 7 -
Communication Process <ul><li>The slides after this page shows the communication process between two hosts across an inter...
Data Flow Through an Internetwork – 1 Ch 7 -
Data Flow Through an Internetwork – 2  Ch 7 -
Data Flow Through an Internetwork – 3 Ch 7 -
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  • This chapter introduces the general functions of the Data Link layer and the protocols associated with it.
  • Media is the physical copper cable, optical fiber, or atmosphere through which the signals travel. A physical network is different from a logical network.
  • Two fundamental concepts in networking are the difference between the logical and the physical network.
  • At each hop along the path, an intermediary device accepts the frames (encapsulated packet) from a medium, decapsulates the frame, and then forwards the packets in a new frame appropriate to the medium of that segment of the physical network.
  • Each frame type has three basic parts: header, data and trailer.
  • The Data Link layer is often divided into two sub-layers.
  • Data Link layer protocols are generally not defined by Request for Comments (RFCs). Although the Internet Engineering Task Force (IETF) maintains the functional protocols and services for the TCP/IP protocol suite in the upper layers, IETF does not define the functions and operation of that model&apos;s Network Access layer.
  • The topology of a network is the arrangement or relationship of the network devices and the interconnections between them. Network topologies can be viewed at the physical level and the logical level.
  • There are benefits to using a layered model to describe network protocols and operations.
  • A physical point-to-point connection.
  • A logical point-to-point connection between two nodes may not necessarily be between two physical nodes at each end of a single physical link.
  • Each frame type has three basic parts: header, data and trailer.
  • The field names above are non-specific fields listed as examples. Different Data Link layer protocols may use different fields from those mentioned.
  • IPv6 features
  • Technology is determined by the size of the network – in terms of the number of hosts and geographic scope – and the services provided by the network. Difference in bandwidth normally results in the use of different protocols for LANs and WANs.
  • The following assumptions are made for this communication. All routing tables are converged ARP tables are complete A TCP session is already established between client and server DNS lookup for the www server is already cached at the client PPP has already established a physical circuit and has established a PPP session
  • Consider an internetwork that requires three subnets.
  • Consider this example with five LANs and a WAN for a total of 6 networks.
  • Chapter7

    1. 1. Ch 7 - Chapter 7 Data Link Layer
    2. 2. Objectives <ul><li>Explain the role of Data Link layer protocols in data transmission </li></ul><ul><li>Describe how the Data Link layer prepares data for transmission on network media </li></ul><ul><li>Describe the different types of media access control methods </li></ul><ul><li>Identify several common logical network topologies and describe how the logical topology determines the media access control method for that network </li></ul><ul><li>Explain the purpose of encapsulating packets into frames to facilitate media access </li></ul><ul><li>Describe the Layer 2 frame structure and identify generic fields </li></ul><ul><li>Explain the role of key frame header and trailer fields, including addressing, QoS, type of protocol and frame check sequence </li></ul>Ch 7 -
    3. 3. Data Link Layer <ul><li>The Data Link layer prepares Network layer packets for transmission and control access to the physical media </li></ul><ul><li>Allows the upper layers to access the media using techniques such as framing </li></ul>Ch 7 - <ul><li>Controls how data is placed onto the media using techniques such as media access control and error detection </li></ul>
    4. 4. Data Link Layer Terminology <ul><li>The following terms are specific to this layer </li></ul>Ch 7 -
    5. 5. Network Types <ul><li>Logical network </li></ul><ul><ul><li>defined at the Network layer by the arrangement of the hierarchical addressing scheme </li></ul></ul><ul><li>Physical network </li></ul><ul><ul><li>represents the interconnection of devices on a common media </li></ul></ul><ul><ul><li>also referred to as a network segment </li></ul></ul>Ch 7 -
    6. 6. Accessing The Media <ul><li>Data Link Layer protocols governs how to format a frame for use on different medium . </li></ul><ul><li>At each hop along the path, an intermediary device accepts the frames ( encapsulated packet) from a medium,& decapsulates the frame. </li></ul>Ch 7 - Ethernet link Satellite link Wireless link
    7. 7. Media Access <ul><li>Layer 2 protocols specify the encapsulation of a packet into a frame and the techniques for getting the encapsulated packet on and off each medium </li></ul><ul><li>The media access control (MAC) methods define the processes by which network devices can access the media and transmit frames </li></ul>Ch 7 -
    8. 8. Creating a Frame <ul><li>The Data Link layer prepares a packet for transport across the local media by encapsulating it with a header and trailer to create the frame </li></ul><ul><ul><li>header – contains control information, such as addressing , and is located at the beginning of the protocol data unit (PDU) </li></ul></ul><ul><ul><li>data – the packet from the Network Layer </li></ul></ul><ul><ul><li>trailer – contains control information added to the end of the PDU </li></ul></ul>Ch 7 -
    9. 9. Control Information <ul><li>Data Link layer protocols require control information to enable the protocols to function </li></ul><ul><li>The control information performs the following function: </li></ul><ul><ul><li>which nodes are in communication with each other </li></ul></ul><ul><ul><li>when communication between individual nodes begins and ends </li></ul></ul><ul><ul><li>what errors occurred between the communicating nodes </li></ul></ul><ul><ul><li>which nodes will communicate next </li></ul></ul>Ch 7 -
    10. 10. Frame Structure <ul><li>Framing breaks the stream into decipherable groupings </li></ul><ul><ul><li>control information is inserted in the header and trailer fields </li></ul></ul><ul><li>The Bits signals the start and stop of the frame </li></ul>Ch 7 -
    11. 11. Frame Fields <ul><li>Frame start and stop </li></ul><ul><ul><li>signal the beginning and end limits of a frame </li></ul></ul><ul><li>Address </li></ul><ul><ul><li>contains the address of the primary or secondary device </li></ul></ul><ul><li>Type </li></ul><ul><ul><li>the type of PDU contained in the frame </li></ul></ul><ul><li>Quality control </li></ul><ul><ul><li>establish, configure, maintain, and terminate the link </li></ul></ul><ul><li>Data </li></ul><ul><ul><li>the frame payload, i.e. the Network layer packet </li></ul></ul><ul><li>Error detection </li></ul><ul><ul><li>check the integrity of the frame </li></ul></ul>Ch 7 -
    12. 12. Data Link Layer Function <ul><li>The Data Link layer is an interface between the upper-layer processes and the Physical layer </li></ul><ul><ul><li>connects the upper layer services to the media </li></ul></ul><ul><li>Usually implemented in the form of a network interface card </li></ul>Ch 7 - <ul><ul><li>contains software functions to prepare data for transmission and encode the data as signals to be sent on the media </li></ul></ul>
    13. 13. *Data Link Sub-layers Ch 7 -
    14. 14. *Data Link Sub-layers (cont’d) <ul><li>Logical Link Control (LLC) </li></ul><ul><ul><li>defines the software processes that provide services to the Network layer </li></ul></ul><ul><ul><li>places information in the frame that identifies which Network layer protocol is being used </li></ul></ul><ul><ul><li>allows multiple Layer 3 protocols, such as IP and IPX, to utilize the same network interface media </li></ul></ul><ul><li>Media Access Control (MAC) </li></ul><ul><ul><li>defines the media access processes performed by the hardware </li></ul></ul><ul><ul><li>provides Data Link layer addressing and delimiting(start & stop) of data according to the physical signaling requirements of the medium and the type of Data Link layer protocols </li></ul></ul>Ch 7 -
    15. 15. Data Link Layer Standards <ul><li>Data Link layer services and specifications are defined by multiple standards based on a variety of technologies and media </li></ul><ul><ul><li>standards may integrate both Layers 1 and 2 services </li></ul></ul>Ch 7 -
    16. 16. Shared Media Access Ch 7 -
    17. 17. Shared Media Access (cont’d) <ul><li>Regulating the placement of data frames onto the media is known as media access control (MAC) </li></ul><ul><li>Data Link layer defines the rules for access to different media </li></ul><ul><li>The * method of media access control used depend on: (Online assessment question) </li></ul><ul><ul><li>media sharing – how the nodes share the media </li></ul></ul><ul><ul><li>topology – how the connection between the nodes appears to the Data Link layer </li></ul></ul>Ch 7 -
    18. 18. *Controlled Access <ul><li>Network takes turn, in sequence, to access the medium </li></ul><ul><ul><li>known as scheduled access or deterministic </li></ul></ul><ul><ul><li>well-ordered and provides predictable output </li></ul></ul><ul><ul><li>can be inefficient because a device has to wait for its turn to use the media => No Collisions </li></ul></ul>Ch 7 -
    19. 19. *Contention-Based Access <ul><li>Allows any device to access the medium whenever it has data to send </li></ul><ul><ul><li>also known as non-deterministic </li></ul></ul><ul><ul><li>no mechanism to track whose turn it is to access the media </li></ul></ul><ul><ul><li>data collision occurs when two or more devices access the media at the same time </li></ul></ul>Ch 7 -
    20. 20. Contention-Based Access (cont’d) <ul><li>Contention-based systems do not scale well under heavy media use </li></ul><ul><ul><li>the probability of successful media access without collision decreases as use and number of nodes increases </li></ul></ul><ul><li>Recovery mechanisms needed to correct errors due to collisions further diminishes the throughput </li></ul><ul><li>To prevent total chaos, a Carrier Sense Multiple Access (CSMA) process is used to detect if the media is carrying a signal </li></ul><ul><ul><li>it is possible that the CSMA process will fail when two devices transmit at the same time – data collision </li></ul></ul><ul><li>CSMA is usually implemented in conjunction with either of the two methods for resolving media contention </li></ul><ul><ul><li>CSMA/Collision Detection ( CSMA/CD ) </li></ul></ul><ul><ul><li>CSMA/Collision Avoidance ( CSMA/CA ) </li></ul></ul>Ch 7 -
    21. 21. *Carrier Sense Multiple Access <ul><li>CSMA/CD </li></ul><ul><ul><li>device monitors the media for the presence of a data signal </li></ul></ul><ul><ul><li>if a data signal is absent , the media is free and the device transmits the data </li></ul></ul><ul><ul><li>if signals are detected, this indicates another device is transmitting and all other device must stop sending and try again later </li></ul></ul><ul><ul><li>this method is used by 802.3 Ethernet networks </li></ul></ul><ul><li>CSMA/CA </li></ul><ul><ul><li>device examines the media, air, of the presence of a data signal </li></ul></ul><ul><ul><li>device sends a notification, Request to Send , across the media of its intent to use it </li></ul></ul><ul><ul><li>device then sends the data </li></ul></ul><ul><ul><li>this method is used by 802.11 wireless networks </li></ul></ul>Ch 7 -
    22. 22. Non-shared Media Access <ul><li>Require little or no control before placing frames onto the media </li></ul><ul><li>The media connects two nodes in a point-to-point topology </li></ul><ul><ul><li>nodes do not have to share the media with other hosts </li></ul></ul><ul><ul><li>Data Link protocols have little to do for controlling non-shared media access </li></ul></ul><ul><li>In point-to-point connections, the Data Link has to consider whether the communication is half-duplex or full-duplex </li></ul>Ch 7 -
    23. 23. Half-duplex Communication <ul><li>Half-duplex communication means that the devices can both transmit and receive on the media but NOT simultaneously </li></ul><ul><li>Arbitration rules for resolving conflicts are used to resolve conflicts such as more than one device attempts to transmit at the same time </li></ul>Ch 7 -
    24. 24. Full-duplex Communication <ul><li>Both devices can transmit and receive on the media simultaneously </li></ul><ul><ul><li>the Data Link assumes the media is available for transmission </li></ul></ul><ul><li>No media arbitration is necessary at the Data Link layer </li></ul>Ch 7 -
    25. 25. Topologies <ul><li>Physical topology </li></ul><ul><ul><li>an arrangement of the nodes and the physical connections between them </li></ul></ul><ul><ul><li>also called the cabled topology </li></ul></ul><ul><ul><li>will most likely not be the same as the logical topology </li></ul></ul><ul><li>Logical topology </li></ul><ul><ul><li>the way a network transfers frames from one node to the next </li></ul></ul><ul><ul><li>consists of virtual connections between the nodes of a network independent of the physical layout </li></ul></ul><ul><ul><li>influences the type of network framing and media access control used </li></ul></ul>Ch 7 -
    26. 26. *Topologies (cont’d) Ch 7 -
    27. 27. Point-to-Point Topology <ul><li>A point-to-point topology connects two nodes directly together </li></ul><ul><li>The media access control protocol can be very simple </li></ul><ul><li>The frames are placed on the media by the node at one end and taken off the media by the node at the other end </li></ul><ul><li>Point-to-point networks can also operate either in half-duplex or full-duplex mode </li></ul>Ch 7 -
    28. 28. Logical Point-to-Point Topology <ul><li>The end nodes communicating in a point-to-point network can be physically connected via a number of intermediate devices </li></ul><ul><ul><li>the use of physical devices does not affect the logical topology </li></ul></ul><ul><ul><li>they may be separated over some geographical distance </li></ul></ul><ul><li>The connection between these nodes form a virtual circuit </li></ul>Ch 7 -
    29. 29. Multi-Access Topology(Bus Topology) <ul><li>Enables a number of nodes to communicate using a shared media </li></ul><ul><li>Data from only one node can be placed on the medium at any one time </li></ul><ul><ul><li>only the node to which the frame is addressed processes the content of the frame </li></ul></ul><ul><li>MAC methods are usually CSMA/CD or CSMA/CA </li></ul>Ch 7 -
    30. 30. Ring Topology <ul><li>Each node in turn receives a frame </li></ul><ul><ul><li>the node removes the frame from the ring and examines the address </li></ul></ul><ul><ul><li>the node passes the frame to the next node if it is not addressed to it </li></ul></ul><ul><li>Only one frame at a time is usually carried by the media </li></ul><ul><li>MAC technique used is * Token Passing </li></ul><ul><ul><li>a node can only place a data frame on the media when it has the token </li></ul></ul>Ch 7 -
    31. 31. The Frame <ul><li>No one frame structure meets the needs of all data transportation across all types of media </li></ul><ul><li>The amount of control information needed in the frame varies to match the MAC requirements of the media and logical topology </li></ul>Ch 7 -
    32. 32. Role of the Header <ul><li>Start Frame </li></ul><ul><ul><li>the beginning of the frame </li></ul></ul><ul><li>Address </li></ul><ul><ul><li>the source and destination nodes on the media </li></ul></ul><ul><li>Type/Length </li></ul><ul><ul><li>indicates the upper-layer service contained in the frame or frame length </li></ul></ul><ul><li>Priority/Quality of Service </li></ul><ul><ul><li>indicates a particular type of communication service for processing </li></ul></ul>Ch 7 -
    33. 33. Physical Address <ul><li>Devices at the Data Link layer are referred to as physical addresses </li></ul><ul><li>(MAC Address) </li></ul><ul><li>Physical addresses do not indicate on what network the device is located </li></ul><ul><li>The physical address is used only for local delivery </li></ul><ul><ul><li>the frame is used to transport data between nodes </li></ul></ul><ul><ul><li>the physical address has no meaning beyond the local network </li></ul></ul>Ch 7 -
    34. 34. Addressing Requirements <ul><li>Point-to-point topology with just two interconnected nodes does not require addressing </li></ul><ul><li>Multi-access and ring topologies can connect many nodes on a common media </li></ul>Ch 7 -
    35. 35. Role of the Trailer <ul><li>Frame Check Sequence ( FCS ) </li></ul><ul><ul><li>used to determine if errors occurred in transmission and reception </li></ul></ul><ul><ul><li>error detection is used to check the integrity of the data </li></ul></ul><ul><ul><li>data signals could be subjected to interference, distortion or loss </li></ul></ul><ul><ul><li>the transmitting node creates a cyclic redundancy check (CRC) value and places it in the FCS field </li></ul></ul><ul><ul><li>the receiving node calculates the CRC based on the received frame and compares the two CRC value </li></ul></ul><ul><li>Stop Frame </li></ul><ul><ul><li>the end of the frame </li></ul></ul>Ch 7 -
    36. 36. Data Link Protocols <ul><li>The actual Layer 2 protocol used depends on the logical topology of the network and the implementation of the Physical layer </li></ul><ul><li>The Layer 2 protocol used for a particular network topology is determined by the technology. </li></ul><ul><li>*Sending machine needs to discover the Ethernet MAC address of the intended recipient network interface . (Online assessment question) </li></ul>Ch 7 -
    37. 37. Technology <ul><li>LAN technology </li></ul><ul><ul><li>a LAN typically uses a high-bandwidth technology that is capable of supporting large number of users </li></ul></ul><ul><ul><li>its high density of users within a relatively small geographical area makes this technology cost effective </li></ul></ul><ul><li>WAN technology </li></ul><ul><ul><li>not cost effective to use a high-bandwidth technology over large geographic areas </li></ul></ul><ul><ul><li>cost of the long distance physical links typically results in lower bandwidth capacity </li></ul></ul>Ch 7 -
    38. 38. Ethernet Protocol <ul><li>Ethernet is a family of LAN networking technologies that are defined in the IEEE802.2 and 802.3 standards </li></ul><ul><li>Ethernet standards define both the Layer 2 protocols and the Layer 1 technologies </li></ul><ul><li>Ethernet is the most widely used LAN technology and supports data bandwidth of 10, 100, 1000 or 10,000 Mbps </li></ul><ul><li>The basic frame format and the IEEE sub-layers of OSI Layers 1 and 2 remain consistent across all forms of Ethernet </li></ul><ul><li>Ethernet uses unacknowledged connectionless service over a shared media using CSMA/CD </li></ul><ul><li>Ethernet II is the Ethernet frame format used in TCP/IP networks </li></ul>Ch 7 -
    39. 39. *Ethernet Protocol (cont’d) <ul><li>The Ethernet frame uses the media access control (MAC) address of the node as the Data Link layer address </li></ul><ul><ul><li>*48-bit MAC address (hexadecimal format) </li></ul></ul>Ch 7 -
    40. 40. Point-to-Point Protocol (PPP) <ul><li>PPP is a WAN protocol used to deliver frames between two nodes </li></ul><ul><li>PPP can be used on various physical media, including twisted pair, fiber optic and satellite transmission </li></ul><ul><ul><li>to accommodate the different types of media, PPP establishes logical connections, called sessions, between nodes </li></ul></ul><ul><li>The sessions also provide PPP with a method for encapsulating multiple protocols over a point-to-point link </li></ul><ul><ul><li>each protocol encapsulated over the link establishes its own PPP session </li></ul></ul><ul><li>PPP also allows the two nodes to negotiate options within the PPP session </li></ul><ul><ul><li>authentication , compression and multilink (the use of multiple physical connections) </li></ul></ul>Ch 7 -
    41. 41. Point-to-Point Protocol (cont’d) <ul><li>Figure shows the basic fields in a PPP frame </li></ul>Ch 7 -
    42. 42. Wireless Protocol <ul><li>802.11 is an extension of the IEEE 802 protocol </li></ul><ul><ul><li>uses the same 802.2 LLC and 48-bit addressing scheme as 802 LANs </li></ul></ul><ul><ul><li>commonly referred to Wi-Fi </li></ul></ul><ul><ul><li>contention-based system using CSMA/CA </li></ul></ul><ul><ul><li>supports authentication, association (connectivity to a wireless device) and privacy (encryption) </li></ul></ul><ul><li>CSMA/CA specifies a random backoff procedure for all nodes that are waiting to transmit </li></ul><ul><ul><li>medium contention is most likely just after the medium becomes available </li></ul></ul><ul><ul><li>making the nodes back off for a random period greatly reduces the likelihood of a collision </li></ul></ul>Ch 7 -
    43. 43. Wireless Protocol (cont’d) <ul><li>Figure shows the fields in an 802.11 frame </li></ul>Ch 7 -
    44. 44. Communication Process <ul><li>The slides after this page shows the communication process between two hosts across an internetwork </li></ul><ul><li>In each step only the major elements are considered </li></ul><ul><li>Read each explanation carefully and study the operation of the layers for each device </li></ul>Ch 7 -
    45. 45. Data Flow Through an Internetwork – 1 Ch 7 -
    46. 46. Data Flow Through an Internetwork – 2 Ch 7 -
    47. 47. Data Flow Through an Internetwork – 3 Ch 7 -
    48. 48. Data Flow Through an Internetwork – 4 Ch 7 -
    49. 49. Data Flow Through an Internetwork – 5 Ch 7 -
    50. 50. Data Flow Through an Internetwork – 6 Ch 7 -
    51. 51. Data Flow Through an Internetwork – 7 Ch 7 -
    52. 52. Data Flow Through an Internetwork – 8 Ch 7 -
    53. 53. Data Flow Through an Internetwork – 9 Ch 7 -
    54. 54. Data Flow Through an Internetwork – 10 Ch 7 -
    55. 55. Data Flow Through an Internetwork – 11 Ch 7 -
    56. 56. Data Flow Through an Internetwork – 12 Ch 7 -
    57. 57. Data Flow Through an Internetwork – 13 Ch 7 -
    58. 58. Data Flow Through an Internetwork – 14 Ch 7 -
    59. 59. Data Flow Through an Internetwork – 15 Ch 7 -
    60. 60. Data Flow Through an Internetwork – 16 Ch 7 -
    61. 61. Data Flow Through an Internetwork – 17 Ch 7 -
    62. 62. Data Flow Through an Internetwork – 18 Ch 7 -
    63. 63. Data Flow Through an Internetwork – 19 Ch 7 -
    64. 64. Data Flow Through an Internetwork – 20 Ch 7 -
    65. 65. Data Flow Through an Internetwork – 21 Ch 7 -
    66. 66. Data Flow Through an Internetwork – 22 Ch 7 -

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