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Chapter 9. Hardware Addressing & Frame Type Identification. EE 526 Presentation by Ryan Star. Topics To Be Covered. LAN Hardware Addressing Packet Filtering Physical Address Format Broadcasting & Multicasting Packet Type Identification Frame Headers and Format Network Analyzers.

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chapter 9

Chapter 9

Hardware Addressing & Frame Type Identification

EE 526 Presentation

by Ryan Star

topics to be covered
Topics To Be Covered
  • LAN Hardware Addressing
  • Packet Filtering
  • Physical Address Format
  • Broadcasting & Multicasting
  • Packet Type Identification
  • Frame Headers and Format
  • Network Analyzers
introduction local area network
Introduction – Local Area Network
  • LAN technology is used to communicate over short distances
  • Most LANs are shared networks with a physical path to all computers
  • Shared - any signal sent reaches all attached stations
  • Most communication does not involve all stations, but rather just a pair of computers
  • At a given station the network interface hardware detects the signal and extracts the frame
  • How does the correct pair of computers find each other across this shared medium?
lan hardware addressing
LAN Hardware Addressing
  • Physical Address, Hardware Address or MAC Address (media access control address)
  • All transmitted frames contain a fixed header
  • Source field and destination field
  • These fields contain the sender and recipient addresses
  • The NIC (network interface card) at each station accepts or rejects traffic
  • Easy reply to sender
packet filtering
Packet Filtering
  • Independent processing = Powerful
  • CPU and NIC physically separate hardware
  • NIC handles all frame transmission: size checking , frame sending and receiving
  • NIC performs CRC checks without bothering CPU
  • Addressing allows the NIC to filter only the correct packets or frames to the CPU and operating system
  • Frames received for other destinations get discarded
physical address format
Physical Address Format

Three main types of Addressing:

  • Static - 48 bit, IEEE assigns to hardware manufacturer
  • Configurable - manual with switches or electronic with EPROMs (erasable programmable ROM)
  • Dynamic - Automatic at boot up. Random.


  • Static - unique and permanent
  • Dynamic - smaller, but may conflict often
  • Configurable - best of both - small and permanent
broadcasting multicasting
Broadcasting & Multicasting
  • Application sends message to all stations
  • Broadcast – uses physical or reserved broadcast address
  • Inefficient – bothers CPU
  • Multicast – additional multicast address
  • Application passes address to NIC
  • More efficient – doesn’t bother CPU
packet type identification
Packet Type Identification
  • Addressing alone does not tell what’s in the frame, example - images or ASCII (text)
  • Two types of frame identification
  • Explicit Frame Type : Hardware designers specify how and where ID bits are used
  • Implicit Frame Type : Hardware does not include frame type fields, only data
  • Explicit frame types are self identifying by their frame type field
  • Implicit frame types must agree before hand on the frame type or use data space to create a custom type field
frame headers and format
Frame Headers and Format
  • Payload is not fixed in size
  • Preamble – 10101 for synchronization
  • Standard broadcast addresses are all 1s
  • Multicast addresses begin with 1
  • Hexadecimal examples of frame types
  • Standards guarantee device interoperability
non self identifying frames
Non Self-Identifying Frames
  • Computer pair must agree on format before transmission or ….
  • Use part of the data field for type identification
  • Problem – Different organizations have different standards
  • IEEE standardized with 802.2 for interoperability
  • LLC specifies that a type field follows
  • Logical link control / Subnetwork attachment point
  • OUI – Organizationally unique identifier
network analyzers
Network Analyzers
  • Device to monitor and report statistics
  • Usually a laptop with a NIC
  • NIC put in promiscuous mode
  • Accepts all frames without address check
  • Applications - sometimes called a sniffer.
  • Used to debug addressing errors
  • Used to organize and track traffic flow
  • LAN Hardware Addresses (Source & sink Addressing)
  • Packet Filtering (NIC is a traffic cop)
  • Physical Address Format (static, config, dynamic)
  • Broadcasting & Multicasting (CPU usage or not)
  • Packet Type Identification (Implicit or explicit)
  • Frame Headers and Format (Header & payload)
  • Network Analyzers (Task monitor)
chapter 10
Chapter 10

LAN Wiring, Physical Topology & Interface Hardware

topics to be covered1
Topics To Be Covered
  • LAN & Computer Speeds
  • Network Interface Hardware
  • Thick Ethernet Wiring
  • Connection Multiplexing
  • Thin Ethernet Wiring
  • Twisted Pair Ethernet
  • Wiring Scheme Decisions
lan computer speeds
LAN & Computer Speeds
  • Each network technology has a data rate
  • A CPU also has a computation rate
  • Usually the network is faster than the CPU
  • As faster CPUs are invented they become more in line with the speed of the LANs.
  • Typically many different CPU speeds are present on any LAN
  • Example FDDI speed 100Mbs & CPU speed of 800MHz can’t process all the instructions for each bit received
network interface hardware
Network Interface Hardware
  • If CPUs can’t process at LAN rates how does it function?
  • Network interface cards (NICs) handle all transmission
  • NICs are design for specific LAN speeds
  • Most NICs contain DMA direct memory access
  • DMA can TX or RX bits from memory w/o the CPU
  • The NIC only informs the CPU after it’s verified a frame has been correctly delivered or received.
thick ethernet wiring
Thick Ethernet Wiring
  • Thicknet or 10Base5
  • Large coax cable
  • AUI (attachment unit interface) cable
  • Thicknet NIC only handles digital aspects
  • Transceiver – handles analog signaling
  • Coax must be terminated to cancel reflections
connection multiplexing
Connection Multiplexing
  • Thicknet wiring is inconvenient
  • Transceivers must be a certain distance apart
  • Connection multiplexers clean up wiring
  • Act as a transceiver for all computers but only connects to one real transceiver
  • Connects to multiple stations in one easy location
  • Performs all transceiver functions
thin ethernet wiring
Thin Ethernet Wiring
  • Thinner, flexible coax cable
  • Called Thinnet or 10Base2
  • Costs less - transceiver is built into NIC
  • No transceivers, no AUI cables, but still needs termination because it shares the same electrical properties as thicknet
  • Attaches with a BNC type connector
  • What does BNC stand for? Hint: military
twisted pair ethernet
Twisted Pair Ethernet
  • 10BaseT - commonly called Ethernet
  • Connects to a hub with RJ45 (registration jack) connectors
  • Hub - like connection multiplexing
  • Physically a star but logically a bus
  • NIC hides LAN devices so that all work together
  • No termination is required
wiring scheme decisions
Wiring Scheme Decisions
  • Transceivers vs. BNC & hubs
  • Cost – wiring, spacing, conduits, # of computers, current set up.
  • Perhaps all three
  • Mac’s Localtalk – like Thicknet with thin wire and close transceivers
  • Multiple connector NIC
  • Wireless & Fiber Optics
  • LAN & Computer Speeds
  • Network Interface Hardware
  • Thick Ethernet Wiring
  • Connection Multiplexing
  • Thin Ethernet Wiring
  • Twisted Pair Ethernet
  • Wiring Scheme Decisions