Chapter 9. Hardware Addressing And Frame Type Identification - PowerPoint PPT Presentation

Loading...

PPT – Chapter 9. Hardware Addressing And Frame Type Identification PowerPoint presentation | free to view - id: e3b1-OGM1M



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

Chapter 9. Hardware Addressing And Frame Type Identification

Description:

How LAN Hardware Uses Addresses To Filter Packets ... A shared network system uses physical addresses to filter incoming frames. ... – PowerPoint PPT presentation

Number of Views:176
Avg rating:3.0/5.0
Slides: 45
Provided by: jing2
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Chapter 9. Hardware Addressing And Frame Type Identification


1
Chapter 9. Hardware Addressing And Frame Type
Identification
  • Jing Wang
  • Towson University

2
9.1. Introduction
  • Advantage of shared networks
  • Universal connectivity because all computers
    share the medium, a transmitted signal reaches
    all computers
  • This chapter
  • Consider transmission across a shared LAN in more
    detail
  • How a pair of computers communicate without other
    computers to receive and process a copy of each
    message
  • Hardware addressing
  • Network interface hardware
  • Frame type

3
9.2. Specifying A Recipient
  • How can two computers communicate directly across
    a shared medium in which all attached stations
    receive a copy of all signals?
  • Most LAN technologies use an addressing scheme to
    provide direct communication
  • Each station on the LAN is assigned a unique
    numeric value called a physical address, hardware
    address or media access address (MAC address)
  • Each frame begins with a header that contains
    destination address field and source address
    field
  • Network interface hardware accepts only those
    frames in which the destination address matches
    the stations address

4
9.2. Specifying A Recipient
  • Each computer attached to a LAN is assigned a
    number known as its physical address.
  • A frame sent across a LAN contains the address of
    the sending computer, called a source address,
    and the address of the intended recipient, called
    the destination address

5
9.3. How LAN Hardware Uses Addresses To Filter
Packets
  • LAN interface hardware handles all the details of
    sending and receiving frames on the shared medium
  • Checks the length of an incoming frame
  • Checks the CRC
  • Discards frames that contain errors
  • Sends and receives frames without using the
    computers CPU

6
9.3. How LAN Hardware Uses Addresses To Filter
Packets
  • Figure 9.1. Organization of the hardware in a
    computer attached to a LAN. Because it is
    powerful and independent, the network interface
    hardware does not use the CPU when transmitting
    or receiving bits of a frame.

7
9.3. How LAN Hardware Uses Addresses To Filter
Packets
  • LAN interface hardware uses physical addressing
    to prevent the computer from receiving all
    packets that travel across the LAN
  • Compares the destination address in the frame to
    the physical address of the station
  • If match, accepts the frame and passes it to the
    operation system
  • If not, discards the frame and waits for the next
    frame
  • Ignore the frame addressed to a nonexistent
    station

8
9.3. How LAN Hardware Uses Addresses To Filter
Packets
  • A shared network system uses physical addresses
    to filter incoming frames.
  • The network interface hardware, which handles all
    the details of frame transmission and reception,
    compares the destination address on each incoming
    frame to the stations physical address, and
    discards frames not destined for the station

9
9.3. How LAN Hardware Uses Addresses To Filter
Packets
  • Because a network interface operates without
    using a stations CPU, a frame can be transferred
    across a shared LAN from one computer to another
    without interfering with processing on the
    computers

10
9.4. Format Of A Physical Address
  • Static
  • relies on the hardware manufacturer to assign a
    unique physical address to each network interface
  • Configurable
  • provides a mechanism that a customer can use to
    set a physical address
  • Dynamic
  • provides a mechanism that automatically assigns a
    physical address to a station when the station
    first boots

11
9.4. Format Of A Physical Address
  • Static
  • Ease of use
  • Permanence
  • Dynamic
  • Eliminates the need for hardware manufacturers to
    coordinate in assigning addresses
  • Allows each address to be smaller
  • Lack of permanence and potential conflict
  • Configurable
  • Permanent
  • Do not need to be large
  • Can be replaced without changing the computers
    physical address

12
9.5. Broadcasting
  • Broadcasting
  • It makes a copy of data available to all other
    computers on the network
  • Since LANs employ shared media, they make
    broadcasting extremely efficient
  • Extend the addressing scheme
  • A special, reserved broadcast address
  • If a frame arrives with the special broadcast
    address or the stations physical address in its
    destination address, accepts it

13
9.5. Broadcasting
  • The network interface hardware in a computer
    makes a copy of every frame that passes across
    the shared network.
  • The interface accepts the frame and delivers a
    copy to the operating system if the destination
    address in the frame is the reserved broadcast
    address or matches the computers physical
    address.
  • Thus, when a frame is sent to the broadcast
    address, each computer on the network receives a
    copy

14
9.6. Multicasting
  • Multicast
  • A network interface does not automatically
    forward multicast frames to the CPU
  • it is programmed to make decision to accept or
    reject frames

15
9.7. Multicast Addressing
  • Multicast
  • Reserve an additional set of addresses
  • When computer boots, the interface is programmed
    to recognize only the computers address and the
    broadcast address
  • If an application wishes to receive multicast
    frames, it inform the network interface which
    multicast address to use
  • The interface adds the address to the set it will
    recognize, and begins to accepting frames sent to
    that address

16
9.8. Identifying Packet Contents
  • Explicit frame type
  • type information is included in the frame
  • Frame type field - the bits of a frame used to
    identify the contents
  • Self-identifying frame
  • Implicit frame type
  • does not include a type field

17
9.9. Frame Headers And Frame Format
  • Figure 9.2. The general format of a frame sent
    across a LAN. The header contains information
    such as the addresses of the sender and the
    recipient.

18
9.9. Frame Headers And Frame Format
  • Each LAN technology defines a frame format.
  • Most technologies have frames that each consist
    of a header followed by a data area.
  • Because the size and format of the header is
    fixed, all frames used with a given technology
    have the same header format
  • The size of the data area is determined by the
    data being sent in the frame

19
9.10. An Example Frame Format
  • Figure 9.3. Illustration of the frame format used
    with Ethernet. The number in each field gives the
    size of the field measured in 8-bit octets.

20
9.10. An Example Frame Format
  • Figure 9.4. Examples of frame types used with
    Ethernet (type values are given in hexadecimal).
    The table lists only a few examples many other
    types have been assigned.

21
9.11. Using Networks That Do Not Have
Self-Identifying Frames
  • Before any data is sent, the sender and receiver
    agree to use
  • A single format for data
  • The first few octets of the data field to store
    type information

22
9.11. Using Networks That Do Not Have
Self-Identifying Frames
  • Figure 9.5. Illustration of how type information
    can be included in a frame's data area if the
    frame header does not include a type field.

23
9.11. Using Networks That Do Not Have
Self-Identifying Frames
  • IEEE LLC/SNAP
  • Part of IEEE 802.2
  • Logical Link Control (LLC) SubNetwork Attachment
    Point (SNAP) header
  • Logical Link Control
  • Originally designed to be the same for all LANs
    for interoperability, but not used often today.
  • Interoperability is provided by a common network
    layer protocol.
  • SubNetwork Attachement Point
  • Organizationally Unique Identifier (OUI)
  • Identify a particular standards organization
  • Type
  • Type value defined by that organization

24
9.11. Using Networks That Do Not Have
Self-Identifying Frames
  • Figure 9.6. An example of the 8-octet IEEE
    LLC/SNAP header, which is used to specify the
    type of data. The SNAP portion specifies an
    organization and a type defined by that
    organization.

25
9.12. Network Analyzers, Physical Addresses,
Frame Types
  • Network analyzer (network monitor)
  • A device used to determine how well a network
    system is performing
  • Also called network sniffer
  • Consist of a standard portable computer (e.g. a
    notebook PC) with a standard LAN interface
  • Network interface card in promiscuous mode
  • Accept all frames

26
9.12. Network Analyzers, Physical Addresses,
Frame Types
  • A network analyzer is a device that can be
    configured to count or display frames as they
    pass across a shared network.
  • An analyzer obtains a copy of each frame, and
    then uses header fields such as the physical
    source address, physical destination address, or
    type information to determine how to process the
    frame

27
9.13. Summary
  • Each computer attached to the shared network is
    assigned a unique physical address
  • Network interface hardware handles transmitting
    and receiving frames
  • Broadcast packet is only transmitted once on a
    shared LAN
  • Multicast use the network interface hardware to
    examine frames

28
9.13. Summary
  • Physical address could be static, configurable,
    dynamic
  • Frame header includes frame type
  • If not, type information could be placed in an
    LLC/SNAP header in the first few octets of the
    frame data area
  • A network analyzer is a device that can be used
    to debug problems on a network

29
Supplement
  • http//www.mhhe.com/engcs/compsci/forouzan/

30
Chapter 14
Local Area Networks Ethernet
31
Figure 14.1 Three generations of Ethernet
32
Figure 14.2 802.3 MAC frame
33
Figure 14.3 Minimum and maximum length
34
Figure 14.4 Ethernet addresses in hexadecimal
notation
35
Figure 14.5 Unicast and multicast addresses
36
Figure 14.6 Physical layer
37
Figure 14.7 PLS
38
Figure 14.8 AUI
39
Figure 14.9 MAU (transceiver)
40
Figure 14.10 Categories of traditional Ethernet
41
Figure 14.11 Connection of a station to the
medium using 10Base5
42
Figure 14.12 Connection of stations to the
medium using 10Base2
43
Figure 14.13 Connection of stations to the
medium using 10Base-T
44
Figure 14.14 Connection of stations to the
medium using 10Base-FL
About PowerShow.com