Chapter 5: Ethernet

Chapter 5: Ethernet

1. Ethernet

   • transport the bits that make up a data-binding layer frame through network media
   • Ethernet works at the data link layer and the physical layer
   • The OSI model separates routing, framing, and media access capabilities from the data link layer
   • Ethernet encapsulation
     • data bandwidths
       • • 10 Mb/s
       • • 100 Mb/s
       • • 1000 Mb/s (1 Gb/s)
       • • 10 000 Mb/s (10 Gb/s)
       • • 40 000 Mb/s (40 Gb/s)
       • • 100 000 Mb/s (100 Gb/s)
       • Ethernet's LLC sublayer handles communication between the upper and lower layers
       • MAC sublayer
         • The MAC sublayer is the lower sublayer of the data link layer and is implemented by hardware, usually on the computer NIC
           • Data encapsulation
             • includes assembling frames before transmission and disarming frames
             • Plot delimitation
               • includes assembling frames before transmission and disarming frames
             • Addressing
               • The encapsulation process contains the Layer 3 PDU
             • Error detection
               • Each frame contains a trailer used to detect transmission errors
           • Media access control
     • Etherne frame fields
       • Ethernet branch is 64 bytes
         • it is considered a collision fragment or a short weft
       • maximum is 1518 byte
         • consider "jumbos" or giant baby wefts
     • mac addresses
       • MAC and hexadecimal address
         • An Ethernet MAC address is a 48-bit binary value expressed as 12 hexadecimal digits
         • Ethernet identity
           • all nodes received each transmitted frame
           • currently Ethernet uses NIC
           • full duplex switches
       • Frame processing
         • When a device forwards a message to an Ethernet network, it attaches the header information to the frame
         • NIC receives an Ethernet frame, examines the destination MAC address to see if it matches the physical MAC address
       • Unicast MAC Address
         • unique address used when sending a frame from a single transmitting device to a single receiving device
         • sent and received, the destination IP address must be included in the IP packet header
       • MAC broadcast address
         • they have a destination IPv4 address that contains only numbers one (1) in the host portion
         • IPv4 is encapsulated in the Ethernet frame
       • Multicast MAC Address
         • allow a source device to send a package to a group of devices.
         • Multicast addresses can be used in remote games
         • Cómo se pronuncia multicasting is distance learning through videoconferencing
   • Basic notions of switches
     • Layer 2 Ethernet switch uses MAC addresses to make forwarding decisions
     • Obtaining MAC Addresses
       • MAC address table dynamically
       • The switch resends the frames after finding a match between the destination MAC address of the frame
     • Frame Filtering
       • You can complete the MAC address table by examining the MAC address of each frame
       • A switch can have many MAC addresses. This is common when the switch is connected to another switch.
     • Frame Forwarding Methods of Cisco Switches
       • Storage and shipping switching
         • collect only enough information in the buffer to determine to which port the data should be forwarded
         • determines the port of the output interface and forwards the frame to its destination through the designated switch port
       • Switching by cutting method
         • buffer to store frames before sending
         • destination port is busy due to congestion
         • port-based memory buffer
           • frames are stored in queues connected to specific input and output ports
           • transmission of all frames stored in memory due to destination port traffic
         • shared memory buffer
           • the buffer is dynamically linked to the destination port
           • the package can be received by one port and can be transmitted by another
       • Duplex and speed settings
         • Full duplex: both ends of the connection can send and receive data simultaneously
         • Medium duplex: only one end of the connection can send data at a time.
       • MDIX automatic
         • switch detects the type of cable connected to the port and configures interfaces properly
         • use a direct or crossed cable
       • Destination on the same network
         • Physical address (MAC address): used for communications from NIC Ethernet to NIC Ethernet on the same network
         • Logical address (IP address): used to send the packet from the initial source to the final destination.