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INTRODUCTION TO NETWORK (CHAPTER 2 : NETWORK ACCESS) - Coggle Diagram
INTRODUCTION TO NETWORK
(CHAPTER 2 : NETWORK ACCESS)
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The purpose and function of the data link layer in preparing communication for transmission on specific media
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Message Segmentation
Large streams of data are divided into smaller, more manageable pieces to send over the network
By sending smaller pieces, many different conversations can be interleaved on the network, called multiplexing
Each piece must be labeled
If part of the message fails to make it to the destination, only the missing pieces need to be
retransmitted
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Protocol Data Units
As application data is passed down the protocol stack, information is added at each level This is known as the encapsulation process
The form that the data takes at each layer is known as a Protocol Data Unit (PDU)
Data - application layer PDU
Segment – Transport layer PDU
Packet – Network layer PDU
Frame – Data Link Layer PDU
Bits – Physical Layer PDU
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De-encapsulation
The de-encapsulation process works from bottom to top. De-encapsulation is the process used by a receiving device to remove one or more of the protocol headers
The data is de-encapsulated as it moves up the stack toward the end-user application
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Network Addresses
Network layer source and destination addresses - Responsible for delivering the IP packet from the original source to the final destination
Source IP address - The IP address of the sending device, the original source of the packet
Destination IP address - The IP address of the receiving device, the final destination of the packet
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Data Link Addresses
The purpose of the data link address is to deliver the data link frame from one network interface to another network interface on the same network
As the IP packet travels from source to destination it is encapsulated in a new data link frame when it is forwarded by each router
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Encapsulation
The encapsulation process works from top to bottom:
Data is divided into segments
The TCP segment is encapsulated in the IP Packet
The IP packet is encapsulated in the Ethernet Frame
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Devices on the Same Network
The network layer addresses, or IP addresses, indicate the original source and final destination
Network portion – The left-most part of the address indicates which network the IP address is a member of
Host portion – The remaining part of the address identifies a specific device on the network
The data link frame which uses MAC addressing, is sent directly to the receiving device
Source MAC address - address of sending device
Destination MAC address – address of receiving device
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Devices on a Remote Network
Sending to a remote network - the source and destination IP addresses represent hosts on different networks. The data link frame cannot be sent directly to the remote destination host. Therefore the frame is sent to the default gateway (nearest router interface). The router removes the received Layer 2 information and adds new data link information before forwarding out the exit interface
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Data Link Protocols
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Purpose of the Data link Layer
Prepares network data for the physical network
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Data link layer is divided into two sublayers
Logical Link Control (LLC)
Communicates with the network layer
Identifies which network layer protocol is being used for the frame
Allows multiple Layer 3 protocols, suchasIPv4and IPv6, to utilize the same network interface and media
Media Access Control (MAC)
Defines the media access processes performed by the hardware
Provides data link layer addressing and access to various network technologies
Communicates with Ethernet to send and receive frames over copper or fiber-optic cable
Communicates with wireless technologies such as Wi-Fi and Bluetooth
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Media Access Control
:fire: Media access control is the equivalent of traffic rules that regulate the entrance of motor vehicles onto a roadway.
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Physical Topology
Refers to the physical connections and dentifies how end devices and infrastructure devices such as routers, switches, and wireless access points are interconnected
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Logical Tapologies
Refers to the way a network transfers frames from one node to the next. These logical signal paths are defined by data link layer protocols.
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Common Physical WAN Topologies
Point-to-Point - Permanent link between two endpoints
Hub and Spoke - A central site interconnects branch sites using point-to-point links
Mesh - Provides high availability, but requires that every end system be interconnected to every other system Administrative and physical costs can be significant
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Physical LAN Topologies
Star - End devices are connected to a central intermediate device. Use Ethernet switches
Extended Star - Additional Ethernet switches interconnect other star topologies
Bus - Used in legacy networks All end systems are chained to each other and terminated in some form one each end Switches are not required to interconnect the end devices Bus topologies using coax cables were used in legacy Ethernet networks because it was inexpensive and easy to set up
Ring - End systems are connected to their respective neighbor forming a ring. Unlike the bus topology, the ring does not need to be terminated. Ring topologies were used in legacy Fiber Distributed Data Interface(FDDI) and Token Ring networks.
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Half-Duplex Communication
Both devices can transmit and receive on the media but cannot do so simultaneously
Used in legacy bus topologies and with Ethernet hubs
WLANs also operate in half-duplex
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Full-Duplex Communication
Both devices can transmit and receive on the media at the same time
Data link layer assumes that the media is available for transmission for both nodes at any time
Ethernet switches operate in full-duplex mode by default, but can operate in half-duplex if connecting to a device such as an Ethernet hub
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Ethernet Mac Address
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Unicast MAC address
The unique address used when a frame is sent from a single transmitting device to a single destination device
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Broadcast MAC Address
A broadcast packet contains a destination IPv4 address that has all ones (1s) in the host portion indicating that all hosts on that local network will receive and process the packet. When the IPv4 broadcast packet is encapsulated in the Ethernet frame, the destination MAC address is the broadcast MAC address of FF-FF-FF-FF-FF- FF in hexadecimal (48 ones in binary)
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Multicast MAC Address
Multicast addresses allow a source device to send a packet to a group of devices
