Chapter 1, "Networking Basics

1
???? ???? ???? ??? ????

• Chapter 1, "Networking Basics
• ?????? ????
• ??????
• ??? osi
• ????? ?? ???? ????? ??????
• Circuit packet
• Lan wan
• Segment back bone
• Baseband broadband

2
???? ??? ???? ??? ???????

• ??? ???? ??? ??????? ????? ?? ??? ???? ?? ???? ?
  ????????? ??? ????? ??????? ?? ????

3
?? ???? ???? ? ???? ????

• ???? ?? ?? ???????? ?? ??? ????? ?? ???? ?? ????
  data ???? ???? ??? ??? ??? ?? ???????? ???? ???
  ?? ???? ? ?? ?? ??? ? ?? ???? ??? ??? ???? ???
  ?????
• ????? ???????? ?? ?????? ?? ????? network medium
  ???? ?? ???? ??? ????? ???? ??? ???? ? ?? ??
  ????? ??????? ? ?? ..... ????

4

• ???? ??????? ?? ??? ????? ? ?? ????? ?????? ?? ??
  ???? ?????? ?? ???? ?? ???? ??? ?????? ????
  network processing ????? ?? ??? ????? ?? ????
• ???? ???? ?? ???????? ???????? ???? ???????? ????
  ????? ?? ??? ???? ??? ??????? ?? ???? ?????? ??
  ??? ??? ??????? ???? ????? ?? ?? ?????? ????????
  ? ?? ??? ??????? ? ???? ???? ????
• ?? ?? ????? ????? ??? ???? ???? ???? ?? ???
  ?????? ?? ?? ????? ?? ?? ?? (??? ? ?? ) ????? ??
  ???? ?? ??? ?? ?? ???? ????? ? ?????? ???? ???
  ????? ?? software ????? ? ?? ????? ??? ?? ??
  ????? ?? ?? text ? ?? ??? ? ?? ????? ?? ????

5
????? ?????? ?? ?????? ??? ?? ????? ?? ????

• Packet acknowledgment.  This is the transmission
  of a return message by the recipient to verify
  the receipt of a packet or packets. A packet is
  the fundamental unit of data transmitted over a
  LAN.
• Segmentation.  This is the division of a lengthy
  data stream into segments sufficiently small for
  transmission over the network inside packets.
• Flow control.  This is the generation by a
  receiving system of messages that instruct the
  sending system to speed up or slow down its rate
  of transmission.
• Error detection.  This is the inclusion of
  special codes in a packet that the receiving
  system uses to verify that the content of the
  packet wasn't damaged in transit.
• Error correction.  This is the generation by a
  receiving system of mess-ages that informs the
  sender that specific packets were damaged and
  must be retransmitted.
• Data compression.  This is a mechanism for
  reducing the amount of data transmitted over a
  network by eliminating redundant information.
• Data encryption.  This is a mechanism for
  protecting the data transmitted over a network by
  encrypting it using a key already known by the
  receiving system

6
?????? ?? ????? ???? ?? ????

• ????? ????? ??? ?????? ?? ???? ?? ????? ?????????
  ????? ?? ???? ?? ?? ??????? ?????? ???????

7
??????

• ?? ???????? ?? ???? ?????? ?? ?????? ??? ??????
  ???? ?? ???? ?? ???? ??? ?? ?? ???????? ????
  ??????
• ??? ?????? ?? ?? ???? ??? ????? ???? ????? ???
  ??? (?? ??? ???? )
• ????? ??? ?????? ?? ????? ????? ????????? (OPEN)
  ?? ???? ??? OSI ?? ????
• ???? ?????? ????? ?? ???? ?? (LINK LAYER) ?? ???
  OSI ??? ?? ??? ?? ???? ??? ???? ?????? ??? ????
  ??? ?? ????

8
protocol

• ???? ???? ??? ??? ???? ??? ???? ???????? ?? ??
  ???? ? ?? ?? ????? ???? ? ?? ?????? ???????
  application ?? ?? ????? ??????? ???? ??? ?? ????
  ????? ???? ???? ? ?? ?? ???????? ?? ???? ???? ???
  ????? ( different platform) ?? ??? ?? ???? ???
  ????? ??? ????? run ??? ??? ?? ?? ?????? ?? ????
  ?? ???? . ??? ?? ??????? ????? ?? ???? ???????
  ????? ???? ??????? ?? ?? ?? ???? ?? ???? ???? ?
  ??? ??????? ?? ???? ????? (protocol) ?? ????

9
??????

• ?? ????? ?????? ?? ?? ???? ??? ????? ????? ????
  ??? ????? ???? ???? ?? ?????? ??????? ???? ??
  ????? ?? ???????? ?? ??????? ?? ???? ??? ??????
  ??? ??????? ?? ?? ???? ?????
• ?? ????? ?? ????? ???? ???? ????? ???? ?????? ???
  ???? ?? ???

10
?????? ?? ?? ???? ??? ????? osi ????? ??? ?? ????

• ???? ??????? ?? ???? ??? ?????? ???? ???? ?????
  ?? ?????? ?? ??? ?????? ??? ????? ?? ??? ????
  ???? ???? ?? ?????? header ?? ??? ??????? ?????
  ?? ????
• Header ?????? ?? ????? ?? ??? ?? ?? ??????
  ?????? ?? ???
• ??????? ???? ?????? ?????? ?????? ? data ??????
  ?? ???
• H4data

11
?????? ?? ?? ???? ??? ????? osi ????? ??? ?? ????

• ???? transport ??? ?? ????? ???? header ???? ??
  ?? ???? ???? ??? ???? ????? ?? ???
• ???? network ??? header ???? ?? ?? ??????
  header ???? ?????? ????? ?? ???
• H4h3data
• ??????? ?? ???? datalink ?? ??? ? ?? ???? ????
  ?????? ??? ???? ????? ??? ???
• H4h3h2data

12
?????? ?????? ?? ????

• ???? packet ?? ???? ?? ??? ??? ?????? ?? ?? ???
  ?? ??? ??? ???? ?? ???
• ??? ?????? ?? ?? ?? ???? header ?????? ?? ?? ????
  ???????? ??? ?? ???? ? ???? ?? ?? ???? ?????
  ????? ?? ??????
• ???? ??? ?????? ???? ?? ??? ??????? ???? data ??
  ?????? ??????? ???? ??????? ?? ???

13
data encapsulation

• ???? ?? ?????? ?????? ???? ?? ?????? header ??
  ???? ????? ??? ???? application ????? ?? ????
  ?? ??? ?????? data encapsulation ???????

14
????? ?????? ????? ?? ???????? ?????? ????? ??????

• ?????? ????? ????? ???????? ? ??????? ??????
  ????? ????? ?? ???? ????? ???? ?? ???
• ?????? ????? ????? ???????? bus ? ?? star ? ??
  ring ?? ???? ????? ???? ?? ??? ????? ?? ???
  ????? ??? ?????? ????? ??? ???? coax ? ???? ?
  ??? ??? udp ? ???? ??? ?? ?? ???? ????? ???? ??
  ???

15
lan

• ???? ??? lan ?? ????? ??? ??? ?? ?? ?????? ??
  ????
• ???????? (??????(
• ????? ?? ?? ???????? ?? ?? ??? ????? ?? ??? ??
  ????? ?????? ( network mediun)
• ??????
• ?????? ???????? ? ?? ??? ????? ?????? ????
  ????? ????? ???????? ?? ????? ?? ?????? ???? ????
  ?? ?? ???? ?? ( data link) ,???? ???? ??? ????? ?
  ?? token ring

16
wan

• ???? ??? lan ?? ???? router ??? ???? ??? ? ????
  wan ???? ?? ????

17
wan connection

• ???? ????? ???? ??? lan ?? wan connection
  ??????? ?? ???? ?????? ????? connection ???
  ???? ????? ? ?? ???? ? ?? ????? ??????? ??? ????
  ???????? ?? ??????? ?? ???

18

• WAN connections ?? ????? ???? ?? ???? ?? ?????
  ???? ????? ?? ????? ????? ?? ??? ???? ?? ???
• ???? ??? ?? ???? lan ?? ?? ?? ??? ????? ???? ????
  ? ?? ?????? ?? ???? ?? ?? leased ??? ???? ????
  ?? ?????? ?? leasd ?? ???? ???? ???? ? ???? ?? ??
  ???? lan ????? ?????

19
baseband

• Base band ?? ?? ???? ??? ?? ?????? ??? ????
  ????? ?? ???? ?? ????? ?? ?? ???? ??? ?? ????????
  ?? ????? ?? ???? ????? ????? ??? ?? ??? ???? ????
  ????? ?????????? ??? ?? ?????? base band
  ??????? ??? ???? ?? ???????? ?????? ?????? ??? ??
  ?? packet ????? ?? ??? ??? ????? ???????? ??????
  ?? ?????? ?? ???? ????? ?????? ??? ?? ?? ???? ??
  packet ??? ???? ????? ?? ???? ? ?? ???? ?????
  packet ???? ???????? ??? ???? ?? ?????? ?? ????
  ????? ??????

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broadband network

• broadband network ?????? ?? ????? ?????? ?? ??
  ?????? ??? ???? ?????? ???? ? ????? ?? circuit
  switch ?? ???? ??????? ?? ???

21
Segment

• ???? ????? ?? ?? ???? lan ???? ?? ??? ? ???? ??
  ?? ????? ? ??????? ????

22
backbone

• ?? ?????? lan ???? ?? backbone ??? ???? ?? ????

23
OSI reference model

• The OSI reference model illustrates the
  networking process as divided into seven layers
• ?? ??? osi ?????? ???? ?? ??? ???? ???? ?? ???
• This theoretical construct makes it easier to
  learn and understand the concepts involved

24
osi

• ?? ???????? ???? ?? ?????? ??????? application
  ???? ???? ?? ?? ????? ?? ????? ???? ?????? ????
  ??? (??? ie)
• ?? ????? ???? ???? ?? ???? ???????(????? ?????? )
  ???? ???? ??? ???? ?? ????? ??????? ? ?? ????
• ???? ???? ?? ???????? ???? ?? ??? ????? ???? ????
  ???? ?? ??? ?? ?? ???? ?????? ???? ???? ????? ??
  ???? ?? ?? ???? packet ?? ????? ? ???? ?????? ??
  ???? ???? ????? ?? ????

25
At the top of the model is the application that
requires access to a resource on the network, and
at the bottom is the network medium itself

• As data moves down through the layers of the
  model, the various protocols operating there
  prepare and package it for transmission over the
  network

26
Once the data arrives at its destination, it
moves up through the layers on the receiving
system, where the same protocols perform the same
process in reverse.

• In 1983, the International Organization for
  Standardization (ISO) and what is now the
  Telecommunication Standardization Sector of the
  International Telecommunication Union (ITU-T)
  published a document called "The Basic Reference
  Model for Open Systems Interconnection

27
In most cases, single protocols combine the
functions of two or more of the layers in the
model

• and the boundaries between protocols often don't
  exactly conform to the model's layer boundaries

28
the model remains an excellent tool for studying
the networking process

• osi

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encapsulation

• ?? ?????? ???? ???? ?? ?? ???? ?????? ????? ??
  ??????????? ????? ???? ?? ?? ???? ?? ???? header
  ????? ?? ??? ? ??? ?? ?? ?? ???? ?????? ?????? ??
  ???

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each protocol adding headers (and in one case, a
footer) to the information it receives from the
layer above it

• application generates a request for a network
  resource, it passes the request down through the
  protocol stack

31
HEADER ?? ???? ????? ?? ???

• ??????? ?? ???? header ????? ?? ??? ???? ???? ???
  ?? ?? ?????? ?? ???? ?????? ?????
• ??????? ???? ??? HEADER ??????? ?? ????? ??
  ?????? ??? ???? ???? ????? ?? ????

32
The header consists of fields containing
information that is specific to the functions of
that protocol

• original request becomes the
• data field, or payload,
• for the transport layer protocol.

33
The final product, a packet ????? ??? ??????
????? PACKET???? ?????? ????

• ready for transmission over the network

34
Data encapsulation is the process by which the
protocols add their headers and footer to the
request generated by the application

• The procedure is functionally similar to the
  process of preparing a letter for mailing. The
  application request is the letter itself, and the
  protocol headers represent the process of putting
  the letter into an envelope, addressing it,
  stamping it, and mailing it.

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a letter for mailing

• The procedure is functionally similar to the
  process of preparing a letter for mailing. The
  application request is the letter itself, and the
  protocol headers represent the process of putting
  the letter into an envelope, addressing it,
  stamping it, and mailing it.

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Physiaval layer

• ??? ??? ?? ???? ? ?? ???? ? ?? ????? ?.... ??
  ????
• ???????? ???? (??????) ????? ?? ???? ??????? ??
  ????
• ??? ?????? ???? ?????? ??? ? ?? ?? ?? ?????? ???
  ???? ?? ????
• ??? ????? ??? (???? ???? ) ??? ??? ???? 2 ? ????
  ?????? ??? ?? ?????? ???? ???? ?? ????
• ??? HUB ??? ????? ?? ?????? ???? ???? ?? ????

38
Physical Layer

• nature of the network's hardware elements, such
  as what medium the network uses, how the network
  is installed, and the nature of the signals used
  to transmit binary data over the network. The
  physical layer also defines what kind of network
  interface adapter must be installed in each
  computer and what kind of hubs (if any) to use

39

• ???? ??? ???? ??????? ??? ?? ???? lan ???? ?? ???
  ???? ?????? ?????? ??? ???? ????? ?? ?????? ???
  ???? data link ????
• ???? ??? ?? ???? datalink ?? ?????? ?????? ??
  ???? ????? ???? ?? ??? ??????? ???? ???? ??????
  ????? ?? ??? ?????? ?? ???? ????? ???? ?? ???.

40
Physical layer

• Physical layer options include various types of
  copper or fiber optic cable, as well as many
  different wireless solutions. In the case of a
  LAN, the physical layer specifications are
  directly related to the data-link layer protocol
  used by the network. When you select a data-link
  layer protocol, you must use one of the physical
  layer specifications supported by that protocol.

41
?????

• ????? ?? ?????? ?????? datalink ?? ???? ? ????
  ???? ??? lan ?? ???? ?? ?????? ??? ??? ??????
  ?? ???? ?????? ?? ???? ????? ???? ?? ??? ???
• coaxial cable
• twisted pair cable
• fiber optic cable
• ????? ?? ??? 1970 ??????? ????? ?? ?? ??? ????
  ????? ???? ??? 10M,100.1G ?? ????? ?????

42
?????? ??? ???? ???? ????? ?? ???? ??????

• ?? ???? ???? UTP ??? ???? COAX ? ?? ???? ? ??
  ....?????? ???
• ?????? ?? ????? ??? ???? ?? ?????? ?? ??? ??????
  ?????? ???? ?? ??? ??? ??? ???? ? ?? ???
  connector ? ?? ??? ????????
• ???? ?? ???? ??? ??? ?? ?????? ????? ???? ?? ??
  ????? ????? ???
• ? ????? EIA/TIA 568A ??? ?????? ?? ????????? ????
  ? ?????? ?? ???? ?? ??? documet ??????? ???

43
Ethernet is a data-link layer protocol that
supports several different physical layer options

• coaxial cable
• twisted pair cable
• fiber optic cable

44
Ethernet Standards
45
Fast Ethernet specifications,

• IEEE 802.3z
• IEEE 802.3ab,
• which are the 1000-Mbps Gigabit Ethernet
  standards
• ???? ???? ????? 802.3 ????? ???? ? ?? ????
  ETHERNET TYPE ?????? ???? ?????? ?? ?? ?????

46
?????? ????? IEEE802.3

• Physical layer specifications
• Frame format
• CSMA/CD MAC mechanism

47
Physical Layer Specifications

• types of cables
• topology
• maximum cable lengths
• number of repeaters
• ?? ???? ?? ????? ????? ????? ??????? ???
  attenuation ? crosstalk ? COLLISSION ?? ?? ????
  ?? ????? ??? ???? ??? ?????? ?? ????

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UTP Ethernet (10Base-T)

• from 10 Mbps to 100 or even 1000 Mbps
• link segments up to 100 meters long to connect
  computers to a repeating hub
• Fast Ethernet standard (IEEE 802.3u )
• 100Base-TX uses only two pairs
• 100Base-T4 uses all four wire pairs

50
Fiber Optic Ethernet

• 10Base-FL, 10Base-FB, and 10Base-FP
• ?? ???? 10M (??? ???? ???? )
• FIDI ?? ???? 100 ??? ??? ????? ???? ????
  BACKBONE ?? ????
• 100 Mbps fiber optic option, 100Base-FX.
  100Base-FX uses the same hardware as 10Base-FL,
  but it limits the length of a cable segment to
  412 meters
• Gigabit Ethernet is the newest form of
• Ethernet, raising network transmission speed to
  1000 Mbps

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specifications for each of these options

• include a great deal of detailed information
  about the physical layer requirements, such as
  the exact type of cable and connectors to use,
  how long the cables can be, how many hubs you can
  have, and many other factors.

52
These specific conditions are required for the
protocol to function properly
53
EIA/TIA 568A

• . This document includes detailed specifications
  for installing cables for data networks in a
  commercial environment, including the required
  distances from sources of electromagnetic
  interference and other general cabling policies..

54
????? ????????? ???? ??????? ???? ?????? ???? ??
??? ????? ??????(???? ???????)

• For copper-based cables, these signals are
  electrical charges.
• For fiber optic cables, the signals are pulses
  of light.
• Other types of network media can use radio
  frequencies, infrared pulses, and other types of
  signals

55
????? ????????? ???? ??????? ???? ?????? ???? ??
??? ????? ??????(???? ???????

• ???? ???? ??? ??? ????? ????????
• ???? ???? ???? ????
• ???? ???? ????? ?? ?????? ??? ????? ?? ?
  infrared ????

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physical layer dictates the signaling scheme that
the computers use

• The signaling scheme is the pattern of electrical
  charges or light pulses used to encode the binary
  data generated by the upper layers

57
Ethernet systems use a signaling scheme called
Manchester encoding,.

• and Token Ring systems use a scheme called
• Differential Manchester

58
Data-Link Layer

• The protocol at the data-link layer is the
  conduit between the computer's networking
  hardware and its networking software
• Network layer protocols pass their outgoing data
  down to the data-link layer protocol, which
  packages it for transmission over the network

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DATA LINK ????

• ?????? ??? ???? ???? ???? ???? ??? ???? ???
  ?????? ????? ??? ????? ???????? ?? ?????
• ?????? ??? ???? NETWORK ????? ????? ??? ??
• ?? ?????? ??? ???? DATA LINK ????? ???? ? ??????
  ???? ???? ???? ?? ?? packet ???? ? ???? ??????
  ?? ??? ????? ?????? ????? ?? ???

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When the other systems on the network receive the
transmitted data, their data-link layer protocols
process it and pass it up to the network layer
61
?????? ??? ????? ?? ????? ???? lan

• ???? ?? ?????? ???? ?? ??????? ?? ???? lan ?????
  ???? ??????? ?????? ?? ?????? ????? ?? ??????
  ??????? ??? ?? ???? ???? ???? ?? ??? ????? ?? ???
  
• ???? ????? ?????? ??? ?????? ??????? ??? ?? ????
  ???? ???? ??? ?? ??? ????? ?? ? ??? ????? ??? ???
  ???? ?????
• Network interface adapters
• Network adapter drivers
• Network cables
• Network hubs

62
?????? ???? ???? ? ???? ?? ??????

• ???? ???? ? hub ?? ?? ???? ?? ?????? ???? ?????
  ?? ???? ? ???? ??????? ???? ?????? ??? ???? ???
  ?????
• ???? ?? ???? ?? ??? ???? ?????? ???? ????? ??
  ???? ??? ??? ???? ?? ?????? ??????

63
?????

• ?? ???? ?????? ????? ??????? ?????? ???? ????
  ?????? ??? ??? . ????? ???? ??? lan ?? ????
  ?????? ????? ???? ??? ???
• Token ring ?? ????? fidi ?? ???? ?????? ??? ????
  lan ?? ?????

64
??????? ?????? ?? ?????? ??? ???? ???? ???? ?????
?????

• A format for the frame (that is, the header and
  footer applied to the network layer data before
  transmission)
• A mechanism for controlling access to the network
  medium
• One or more physical layer specifications for use
  with the protocol

65
??????? ?????? ?? ?????? ??? ???? ???? ???? ?????
?????

• ????? ????
• ???????? ???? ?????? ?? ????? ??????
• ????? ?????? ?? ???? ??? ???? ?? ?????? ???
• ????? ?????? ??? ???? utp ? ?? ???? ? ??
  wireless ?...?? ????

66

• The data-link layer protocol encapsulates the
  data it receives from the network layer protocol
  by adding a header and footer to it, forming what
  is called a frame
• ???? ???? ???? ? ???? ?? ?? ??? ????
• ??? ???? 6 ???? ?? ???? ? ????? ?? ( mac ???? )
  ?? ????

67
Media Access Control

• ?????????? ?? ?? ???? lan ?? ???? ????? ????
  ????? ??????? ????? ?? ?? ?? share ?? ????
• ?? ??? ???? ?????? ???? ???? ???? ?? ?? ????????
  ?????? ??????? packet ?????? ?? ????? ?????? ???
  ????? ????? ?? ????
• ???? ??????? ?? ????? collission ?????? ??????
  ??? ???? ?? ???????? ?? ????? ???
• ????? ??????? ?? ???? lan ?? ???? half duplex
  ?? ????

68
?????? ????? ?? ??????? CSMA/CD ??????? ?? ???

• ?????? TOKEN RING ?? ??????? ???? ??? ??? TOKEN
  PASS ??????? ?? ???

69
WAN links protocol

• There are other data-link layer protocols used
  for WAN links, however, such as the Serial Line
  Internet Protocol (SLIP) and the Point-to-Point
  Protocol (PPP), which do not include physical
  layer information

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71
router

• A router connects two networks together, forming
  an internetwork.
• Unlike bridges and switches, routers function at
  the network layer of the OSI reference mode

72
Routers

• ???? ?? ?? ???? network ??? ?? ????
• Packet ???? ?? ???? ???? ?? ???? ?? ?? ???? ??
  ???? ??? physical ? datlink ??? ?? ?? ????
  network ?? ?????? .??? ???? ???? data link ?? ???
  ???? ? ???? ???? ???? ?? ?? ??? packet ?? ?????
  ??? ???? ???? ?? ???? ? ?? ???? ???? data link
  ?? ?? ???????? ???? ?? ?? ???? ???? ????? ?? ???
  ????? ?? ???

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router

• ???? ?????? ??? ?????? ???? ?? hub ? bridge ?
  switch ????
• ???? ?? ???? ??? broadcast ?? ?? ??? ???? ???
  ???? (?? ?? ????? ??? )
• ???? ???? ?? ?? ???? ?? ???? ???? ????? ?? packet
  ?? ??? ???? ?? ??? ??? ????? ???? ?? ???? ??????
  ?????
• ???? ?? routing table ?? ??? ????

74
WAN links

• In addition to connecting networks at a single
  location, such as a corporate internetwork,
  routers can also connect distant networks using
  WAN links
• ???? ?? ????? ?? ????? ????? ???? ?? ?? ????
  (???? ?? ??????? ??? ???? ) ?? ????? ?? ???? ????
  ?? ?? ?? ????? ???? ?? ???? ???? ????? ?????? wan
  link ???? ???

75

• ?? ?????? ?? ???? ??????? ? ?????? ? ???? ?
  ??????? ????? ?? ???? ?? ???? ????? ????? ?? ??
  ?????? ?? ???? ???? lan ???? ???? ????? ?????
  ???? ??? ?? ?????? ??? ???? ?? ?? ?? ???? ????
  ????? (leased line) ? ?? ???? ?????? ??? ?????
  ??? ???? tellabs , ? ?? alcatel ????? ?? ??
  ????? ????(wan tecnology)

76
??? header ?? ?? ???? network ???? ?????? ip
?? ???? ????? ?? ???? transport ????? ?? ??? 20
bayte ?? ????ip data gram format
77
Version (4 bits).  This field specifies the
version of the IP protocol used to create the
datagram. The version in current use is 4, but IP
version 6 is currently in development. Internet
Header Length (IHL, 4 bits).  This field
specifies the length of the datagram's header, in
32-bit (4-byte) words. The typical length of a
datagram header is five words (20 bytes), but if
the datagram includes additional options, it can
be longer, which is the reason for having this
field. Type Of Service (1 byte).  This field
contains a code that specifies the service
priority for the datagram. This is a rarely used
feature that enables a system to assign a
priority to a datagram that routers observe while
forwarding it through an internetwork. The values
provide a trade-off among delay, throughput, and
reliability. Total Length (2 bytes).  This field
specifies the length of the datagram, including
that of the Data field and all of the header
fields, in bytes. Identification (2
bytes).  This field contains a value that
uniquely identifies the datagram. The destination
system uses this value to reassemble datagrams
that have been fragmented during transmission.
Flags (3 bits).  This field contains bits used
to regulate the datagram fragmentation process.
Fragment Offset (13 bits).  When a datagram is
fragmented, the system inserts a value in this
field that identifies this fragment's place in
the datagram.
78
Time To Live (TTL, 1 byte).  This field specifies
the number of networks that the datagram should
be permitted to travel through on the way to its
destination. Each router that forwards the
datagram reduces the value of this field by one.
If the value reaches zero, the datagram is
discarded. Protocol (1 byte).  This field
contains a code that identifies the protocol that
generated the information found in the Data
field. Header Checksum (2 bytes).  This field
contains a checksum value computed on the IP
header fields only (and not the contents of the
Data field) for the purpose of error detection.
Source IP Address (4 bytes).  This field
specifies the IP address of the system that
generated the datagram. Destination IP Address
(4 bytes).  This field specifies the IP address
of the system for which the datagram is destined.
Options (variable).  This field is present only
when the datagram contains one or more of the 16
available IP options. The size and content of the
field depends on the number and the nature of the
options. Data (variable).  This field contains
the information generated by the protocol
specified in the Protocol field. The size of the
field depends on the data-link layer protocol
used by the network over which the system will
transmit the datagram
79
IP Addressing

• ?????? ip ?? ????? ???? ??? ???? ?? ????? ????
  ??? ?? host ?? ?? ?? ???? ?? ?? ????? ????
• ?????? ipx ?? ????? ???? ??? ???? ???? ? ?? mac
  ???? ???? ???? ??? ???????? ?? ?? ???? lan
  ??????? ?? ???
• ?????? netbbeui ?? ????? ???? ??? ????? ?? ????
  ?? ???? ? ?? ??? ???? ???? ??? ??????? ?? ???

80
IP addressing

• Host ???? ???? ???? ?? ????

81
The Network Layer

• ??? ???? ????? ?????? data ?? ?? ???? ????? ??
  ????? end to end) ( ???? ???? ???? ?? ??? ????
  ????? ?????? data ?? ???? ?? ???? ????? ?? ????
  (???? ??? ??? ???? ? ???? ????? ????? ???? ?????
  ???? ????? ????)
• ?????? IP ?? ???? NETWORK ??? ????? ?? ?????
  ????
• ?? ??? ???? NOWEL ?????? IPX ?? ????? ????? ???
• ? ?????????? ?????? NETBIOS ?? ????? ????? ???
  ?? ?? ???? ???? ????? ?? ????

82

• ?????? ??? ??? ???? ?????? ???? ???? HEADER
  ?????? ?? ?? ???? (DATA) ????? ?? ????
• ???? ?? ?? ???? ??? ???? ????? ?? ??? datagram
  ??? ????

83
Addressing ???? ??? ?? ???? network

• ?????? ip ?? ???? ???? ? ?? ???? ???? ?? ??
  header ??? ???? ???? ?? ??? ??? ???? ???? ????
  ????? ?? ????
• ???? ???? ???? ?? web server ?? ?? browser ????
  ?? ???? ??? 192.168.16.20
• ???? ip ?????? ??????? ???? ? ???? host ?? ????

84
??? ??? ????? ???? ??? ???? ?????? ??? ????
85
Fragmenting

• ???? ???? ????? ??? ?? ???? network ?? ????? ??
  ???? ????? ??????? ?? ???? ??? ????? ???? ??????
  ??? ? ??????? ??? ???? ??? ???? ???? ?? ????
  ????? ?? ???? ???? ???? ????? ?? ???
• ????? ???? 1500 ????
• Token ring 4500 ????

86
Routing

• Routing is the process of directing a datagram
  from its source, through an internetwork, and to
  its ultimate destination using the most efficient
  path possible
• ??????? ??? ?? ???? ???? (datagram) ?? ???? ? ??
  ???? ???? ??? ????? ?? ???? ????? ?? ????? ? ????
  ????? ?? ???? ????????? ???? ?? ?? ?????? ?? ???

87
????? ????

• ????? ???? ?????? ?????? ????? ?? ?? ???? ? ?????
  ??? ?????? ??? ?? ???? ???? ?? ????? ?? ????
• ?? ?? ???????? ???? ???? ??? ????? ????? ?????
• ???????? routing(???? ???? ) ???? ???? ????? ??
  ???
• ???? ?? ??????? ????? ?? ???? ???? ?? ?? ??
  ?????? ?? ????? ??????? ?? ???? routing table

88
Identifying the Transport Layer Protocol

• ??? ???? ?????? ???? ???? ?? ?? header ??? ???
  ?????? ???? transport ?? ??? ???? ???????? ??
  ????? ???? ??? ???? ???? ????? ?? ??? ?? ????
  ???? ?? ???? ???? ???? ????? ??? ???? ?? ?? ????
  ???? ????? ???

89
The Transport Layer

• ??? ?????? ??? ???? tcp ???
• ??? ?????? ???? ???? ???? udp ???
• ?????? tcp???? ?????? ip ?? ???? network ??
  ????
• ??????? ????? ??? ?????? ??? ???? transprot ???
  ??? ?? tcp ?? ?????? ?? ??? connetion oriented
  ?? ???? ?? ?????? udp ?? ??? connection less ??
  ????

90

• A connection-oriented protocol is one in which
  the two communicating systems exchange messages
  to establish a connection before they transmit
  any application data. This ensures that the
  systems are both active and ready to exchange
  messages. TCP, for example, is a
  connection-oriented protocol. When you use a Web
  browser to connect to an Internet server, the
  browser and the server first perform what is
  known as a three-way handshake to establish the
  connection. Only then does the browser transmit
  the address of the desired Web page to the
  server. When the data transmission is completed,
  the systems perform a similar handshake to break
  down the connection.

91
additional services

• Connection-oriented protocols also provide
  additional services such as packet
  acknowledgment,
• data segmentation,
• flow control,
• and end-to-end error detection and correction

92
port numbers

• The headers for both TCP and UDP, for example,
  include port numbers that identify the
  applications from which the packet originated and
  for which it is destined.

93
Session Layer

• ???? ?? ????? ?? ?????? ?????? ??????? ????? ???
  ???? ??? dialog ??? ?? ?????? ???? ??? dialog
  ?? ????? ?? ???? ??? ?? ?? ???? ?? ????? ???????
  ???? two-way alternate (TWA) mode ? ?? ?????? ???
  ?? ?? ???? ?? ???? ?? ?????? ????? ??????? ?????
  two-way simultaneous (TWS) mode

94
Session Layer

• ?? ????? check point ?? data stream???
  ????????????? ???? ?? dialog ???? ?? ????
• ???? ??? transport,? network? , data-link, ?
  physical??? ???? ?????? ???? ??????? ?? ????? ???
  ?????? ???? session ?????? ?? ???? ??????? ??
  ??? ???? ???? ?? ?? ????? ???? ????? ?????? ?? ?
  ????? ?? ???? ??? ?????? prezentation ?
  application ???? ?????
• ????? ?? ??? dialog ?? ????? 22 ????? ???? ???
  ???? ???? ????

95
The Presentation Layer

• ?? ??? ???? ??? ?? ?????? ????? ?? ??? ? ?? ?????
  ?????? ??? ????? ?? ? ?????
• Computers running on different platforms can have
  different abstract syntaxes
• the systems can select a transfer syntax that
  provides additional services, such as data
  compression or encryption

96
Application Layer

• ???? ???? ?????? ?? ???? ??????? ?? ????? ????
  ?? ??? osi ???? application ?? ?? ?????
• ?????? ??? ??? ???? ????? ????? ???? ?? ???? ??
  ???? ?? application ?? ???? ?????? ?? ????? ????
  ???? ????? ??? ?????? snmp ?? ????? ???? ?? ????
  ???? mail program ?? ???? ?????

97
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99
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100
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101
hub

• ?????? ???? ???? ???? ???? ????? ??? HUB ?? ????

102
hub

• hubs used on most Ethernet networks are purely
  physical-layer devices
• An Ethernet hub is also called a multiport
  repeater
• A repeater is a device that amplifies a signal as
  it passes through it to counteract the effects of
  attenuation. If, for example
• RJ45 ports
• hubs connect networks at the physical layer and
  are unaware of the data structures operating at
  the higher layers

103
hub

• When data enters the hub through any of its
  ports, the hub amplifies the signal and transmits
  it out through all of the other ports
• ???? ???? ???? ?? ???? hub ?? ??? ????? ????? ???
  ??? ???? ??? ???? ?? ????? ?? ????
• ???? ??????? ???? ??????? ????? ??? ???????? ??
  ?? ???? ?????? ?? ????

104
Smart Hubs

• greater data processing
• provide a service called store and forward
• hub contains buffers
• retransmit them out through specific ports

105
Connecting Hubs

• Almost every Ethernet hub on the market has an
  extra port called an uplink port
• UTP cables contain eight wires in four pairs, and
  each pair consists of a signal wire and a ground
• Computers transmit data over one wire pair and
  receive data over another

106

• straight
• crossover circuit that connects the transmit pins
  to the receive pins
• The uplink port is the one port in the hub that
  does not have the crossover circuit

107
Bridging

• Bridging is a technique used to connect networks
  at the data-link layer
• Bridg ?? ?? ???? ?? ?? ???? data link ??? ?????
  ?? ???
• provides packet filtering at the data-link layer,
  
• they read and process all of the packets
  transmitted over the network segments.

108
Bridging

• bridge functions at the data-link layer, it is
  capable of interpreting the information in the
  data-link layer protocol header
• Data packets enter the bridge through either one
  of the ports, and the bridge then reads the
  destination address in each packet header and
  decides how to process that packet. This is
  called packet filtering.

109
Broadcast unicast multicast

• broadcast message is a packet with a special
  destination address that causes it to be read and
  processed by every computer that receives it. By
  contrast, a unicast message is a packet addressed
  to a single computer on the network, and a
  multicast message is addressed to a group of
  computers on the network (but not necessarily all
  of them). A broadcast domain is a group of
  computers that all receive a broadcast message
  transmitted by any one of the computers in the
  group.

110
Broadcasts

• The most common method computers use to locate a
  particular system on the local network is to
  transmit a broadcast that essentially asks,
• "Does any computer here have this Internet
  Protocol (IP) address
• or this NetBIOS name

111
MAU

• The primary difference in the operation of an MAU
  is that it does not retransmit all incoming
  traffic out through the other ports
  simultaneously. Instead, the MAU transmits a
  packet arriving through port 5, for example, out
  through port 6, and then waits for the packet to
  return to the MAU through port 6, after which it
  transmits it through port 7, waits for it to
  return, and so on.

112
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113
Switching

• There is another type of data-link layer
  connection device, called a switch
• Because they forward data to a single port only,
  switches essentially convert the LAN from a
  shared network medium to a dedicated one
• separate collision domain
• full bandwidth

114
full bandwidth

• LAN using a hub might have 20 or more computers
  sharing the same 10 Mbps of bandwidth. Replace
  the hub with a switch, and every pair of
  computers has its own dedicated 10-Mbps channel

115
throughput

• some switches provide ports that operate in
  full-duplex mode, which means that two computers
  can send traffic in both directions at the same
  time using separate wire pairs within the network
  cable. Full-duplex operation effectively doubles
  the throughput of a 10-Mbps network to 20 Mbps

116
????? hub ? switch

• The difference between a hub and a switch is that
  a hub forwards every incoming packet out through
  all of its ports, and a switch forwards each
  incoming packet only to the port that provides
  access to the destination system

117
switch
118
????? HUB
119
HUB
120
HUB
121
collision domain
122
switch

• each packet takes a dedicated path from the
  source computer to the destination, forming a
  separate collision domain for those two
  computers.
• Switches still forward broadcast messages to all
  of their ports, but not unicasts and multicasts

123
switch

• switch more often found on larger networks
• On the routed network, the backbone must carry
  the internetwork traffic generated by all the
  segments.
• This can lead to heavy traffic on the backbone,
• On a switched network, you connect the computers
  to individual workgroup switches,
• which are in turn connected to a
  high-performance backbone switch, As a result,
  any computer on the network can open a dedicated
  channel to any other computer, even when the data
  path runs through several switches

124
Routing

• A router connects two networks together, forming
  an internetwork. Unlike bridges and switches,
  routers function at the network layer of the OSI
  reference model. This means that a router can
  connect LANs that run completely different
  data-link layer protocols (such as Ethernet and
  Token Ring),

125
Routing

• When a computer on a LAN wants to transmit data
  to a computer on another LAN, the system sends
  its packets to a router on the local network and
  the router forwards them to the destination
  network

126

• A router forwards a packet based on the
  destination address in the network layer protocol
  header

127
Networking Software

• ????? ??? ?????? ?? ?? ?? ???????? ???? ?? ??
  ???? ??? ????? ??? ???? ?client ? directory
  service ?

128
????? ??? ????

• ???? ????? ????? ??? ???? ??????? ??? ???? ??
  ?????? ???? ???? ??? ????? ??? ????? ??? ???????
  ?? ??? ???
• ?? ????? ???? ??????? ??? ???? ?? ?? ???? ????
  ??? ????? ???? ?? ?? ??? ????? ?? ?? ????? ?? ??
  ?? ?? ???? ????? ???
• ????? ??? ????? ?? ??????? ??? ???? ?? ?? ??????
  ?? ??? ????? ??? ???? ? client ? ?? ???? ?? ????
  peer to peer ?? ?????

129
????? ??? ???

• ???? ??????? ??? ????? ??? ????? ?? ?????? ????
  ?? ????? ?? ???? ?????? ???
• Microsoft Windows 2000 Server, Microsoft Windows
  NT Server,
• Novell NetWare,
• UNIX,
• Apple Macintosh

130

• Windows NT 3.1, first released in 1993
• Was MS-DOS kernel
• Windows 2000, which was a major upgrade
• Windows 2000 also offer multitasking
• Windows 2000 is available in three Server
  versions (Server, Advanced Server, and Datacenter
  Server)

131
??????? ??? ???? ?? ????? ??? ????

• File Systems
• Sharing ??? ?? ??????? ??????? ??? ????? ???
  ???? ???? ?? ?? ???? ?? ??? ??? ?????? ?? ?????
  ???? ?? ?? ???? ???? ??????? ????? ???
• Windows 2000 ?? file system ?? ??? NTFS ????
  ??? ????? ????
• ???? ??? DOS ??? ??? ???? ????? FAT ??? ?????
  WIN NT ? WIN2000 ?? ?? ?? ????? ?? ????

132

• When you create NTFS drives during a Windows NT
  or Windows 2000 installation, you can grant
  access permissions for specific files and folders
  to the users and groups on your network
• NTFS drives can be read only by the Windows NT
  and Windows 2000 operating systems

133
Services

• ?? WIN2000 ????? ?? ?????? ?? ???? ?? ??? ??
  ????? ???? ?????? ?? ?? ????? RUN ?? ???
• ?????? ?? ??????? ??? ???? ?? ???? ???? ????? ??
  ????? ?? ???
• ????? ?????? ?? ??? ????? ??? ?? ????? CONFIG
  ????? ???????? ????? BOOT ?? ??? ??? ??????? ??
  ????? ?? ?? LOAD ??? ? ?? ????? ???? ?? ????

134
UNIX

• UNIX is a network operating system originally
  developed in the 1970s
• ??? ????? ???? ????? ?? ????? ??? ???? ? ??????
  ?? ??? ??? ?? ???? ????? ??? ??? ????? ??? ?????
  ? ?? ???? ?? ???? ??? ?? ??? ????? ???? ?? ?? ???
  ?????? ????? ??????

135
UNIX

• UNIX is primarily an application server platform,
  typically associated with Internet services, such
  as Web, FTP, and e-mail servers. As with Windows
  NT and Windows 2000 systems, UNIX systems can
  function as both servers and clients simultaneou

136
client

• A client is a software component that enables a
  computer to access the resources provided by a
  server
• ?????? ?? ?? ??? ??? ????? ???? ????? ?? ???? ??
  ????? ???? ?? ????? ??? browser ??
• ?? ???? ???? ????? ?????? ?? ?????? ???? ????? ??
  ?? ?????? ???? ???? ?? ???? ?? ???? ??? lan ? ??
  ??? ?? ????? ???? ? ?? ???? ???? ?? ?? ??? ??
  ?????? ?????? ??????

137
client

• ?????? ???? ??? ftp ? mail ?????? ???? ?? ???
  client ?? ????? ?? ??? ?? ???? ??? ?????? ??
  ?????? ?????? ?? ???? ??????

138
Windows Clients

• Almost all versions of Windows (including
  Microsoft Windows for Workgroups, Microsoft
  Windows 95, Microsoft Windows 98, Microsoft
  Windows Me, and Windows NT and Windows 2000, in
  both Server and Workstation versions) include
  both client and server capabilities with the
  operating system

139
directory service

• directory service is a database of user accounts
  and other information that network administrators
  use to control access to shared network
  resources.

140
Directory services

• on a peer-to-peer network, each computer
  maintains its own user accounts and security
  settings, whereas
• client/server networks rely on a centralized
  security database or directory service. Directory
  services range from simple flat file databases
  containing a list of accounts to complex
  hierarchical databases that store information
  about a network's many different resources
  hardware, software, and human.

141
ip

• IP ???? ???? ?????? ?? ?????? ?????? ??? TCP/IP
  ?? ????
• ????? ??? ?????? ?????? ?????? ? ??? ?? ???? ????
  ?? ???? ???? ????? ???? ? ????? ???? ???? ?? ????
  ???? ?????? ?? ???? ??? ???? ??? ?????? ?? ????
  ?? ???
• IP ?? ?????? ?? ??? CONNCTIONLESS ?? ????

142
ip

• TCP ? ?? UDP ???? ?? ?? ?? ???? NETWORK ?????
  ?? ???? ? ?????? IP ?? ??? ???? ?? HEADER ??
  ??? ???? ????? ?? ??? ?? ??????? ??? ???? ?? ????
  ??? ?? ?????? ?? ??? ????? ???? DATAGROM ???? ??
  ???
• Datagram ???? ???? ???? ??? ?? ??????? ???? ??
  ???? ?????
• Datagram ?? ???? datalink ???? ?????? ?????
  ???? ?? ???

143
ip

• datagram?? ?????? ?????? ? ???? ?? ???? ?????
  datalink ??? ?? ???? ????? ??? ????? encapsulate
  ?? ??? ??? ??? ???? ???? ????? ???? ?? ????

144
IP Standard

• ??? ?????? ?????? ?? ?????? ?? ?????? ?? ??? RFC
  ???? IETF ????? ?? ???
• www.ietf.org
• Rfc791 ip

145
IP Functions

• Encapsulation.  The packaging of the transport
  layer data into a datagram
• Addressing.  The identification of systems in the
  network using IP addresses
• Routing.  The identification of the most
  efficient path to the destination system through
  the internetwork
• Fragmentation.  The division of data into
  fragments of an appropriate size for transmission
  over the network
• Protocol identification.  The specification of
  the transport layer protocol that generated the
  data in the datagram

146
IP

• IP is the protocol responsible for transmitting
  data from its source to its final destination.
• IP is a connectionless protocol

147
IPICMP

• IP also carries other types of information in its
  datagrams, including ICMP messages, which notify
  systems of errors and other network conditions,
  and messages generated by routing protocols like
  GGP and EGP, which TCP/IP systems use to
  automatically update their routing tables

148
TCP

• TCP is a connection-oriented protocol that
  provides reliable service with guaranteed
  delivery, packet acknowledgment, flow control,
  and error correction and detection.
• TCP is designed for the transmission of large
  amounts of data that require perfect bit
  accuracy, such as program and data files

149
TCP

• Transport layer protocols encapsulate data that
  they receive from the application layer protocols
  operating above them by applying a header, just
  as the protocols at the lower layers do

150
UDP

• UDP is a connectionless protocol that provides
  unreliable service. It is used primarily for
  short transactions that consist of a single
  request and reply. Not surprisingly, TCP
  generates much more control traffic as it
  provides all of these services, whereas UDP's
  overhead is quite low.

151
transpotport numbers

• All of the common Internet applications have
  particular port numbers associated with them
• ?? application ??? ?? ?? ????? ???? port number
  ????
• Web servers use port 80,?? ???? ??????? ????? ??
  ???? ???? 80 ?? ?????
• DNS servers use port 53
• FTP uses TCP ports 20 and 21

152
transpotport numbers

• IP address port number socket
• 192.168.2.1021 ???? ??? ????
  ?? ftp ?? ???? ?? ???
• http//www.myserver.com81
• IANA port numbers are recommendations,
• ?????? ??? ????

153

• The IANA only controls port numbers from 1 to
  1023

154
ROUTER
155
ROUTER 7200
156
router
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