mcgraw-hill©the mcgraw-hill companies, inc., 2000 chapter 13 the internet
TRANSCRIPT
McGraw-Hill ©The McGraw-Hill Companies, Inc., 2000
Chapter 13
The Internet
McGraw-Hill ©The McGraw-Hill Companies, Inc., 2000
Know how the Internet began.Know how the Internet began.
Understand the architecture of today’s Internet and its relation-Understand the architecture of today’s Internet and its relation-ship with ISPs. ship with ISPs.
Understand the importance of the TCP/IP protocol suite. Understand the importance of the TCP/IP protocol suite.
After reading this chapter, the reader should After reading this chapter, the reader should be able to:be able to:
OOBJECTIVESBJECTIVES
Understand the role of IP, UDP, and TCP in the Internet. Understand the role of IP, UDP, and TCP in the Internet.
Understand the difference between the Internet, an intranet,Understand the difference between the Internet, an intranet,and an extranet.and an extranet.
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HISTORYHISTORYANDAND
ADMINISTRATIONADMINISTRATION
HISTORYHISTORYANDAND
ADMINISTRATIONADMINISTRATION
13.113.1
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RFCs can be found atRFCs can be found athttp://www.rfc-editor.orghttp://www.rfc-editor.org
Note:Note:
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Figure 13-1
Internet today
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Technical Focus:Technical Focus: Maturity Levels of an RFCMaturity Levels of an RFC
An RFC, during its lifetime, falls into one of six maturity levels: proposed standard, draft standard, Internet standard, historic, experimental, and informational.
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Figure 13-2
Internet administration
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TCP/IPTCP/IPPROTOCOLPROTOCOL
SUITESUITE
TCP/IPTCP/IPPROTOCOLPROTOCOL
SUITESUITE
13.213.2
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Figure 13-3
TCP/IP protocol suite
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Figure 13-4 IP datagram
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Technical Focus:Technical Focus: Inside the Header of an IP DatagramInside the Header of an IP Datagram
An IP datagram contains several fields. The most important are the source and destination addresses of the datagram (IP addresses). The header also contains fields related to fragmentation. The size of a datagram may be too large for some LAN or WAN protocols. In this case, the datagram is divided into fragments; each fragment carries the same identification number as well as other information to help the receiver assemble the datagram. The header also has two length fields; one defines the length of the header, the other defines the length of the entire packet. One field that can decrease traffic on the Internet holds the number of routers a packet can visit before it is discarded. The header also contains a checksum field to determine the validity of the packet.
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Figure 13-5
Internet address
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Technical Focus:Technical Focus: Classful versus Classless AddressingClassful versus Classless Addressing
With more and more organizations wanting to use the Internet, the Internet authorities are running out of IP addresses. Internet addresses were originally designed as classful addresses. By this, we mean that the total number of 32-bit addresses was divided unevenly into five classes: A, B, C, D, and E. Class A and B contain blocks of addresses with a very large range. Each block is granted to one organization, but most of these organizations never use their allotted number of addresses. This is a tremendous waste of addresses.
Recently, a new design called classless addressing has been implemented. In this design, all available addresses are put into a big pool; each organization is granted a range of addresses according to its need.
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Figure 13-6 A part of the Internet
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Figure 13-7UDP user datagram
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Technical Focus:Technical Focus: Inside a UDP headerInside a UDP header
The header of the UDP datagram is very simple: it contains only four fields. One field defines the application program that has sent the packet (the source), and another defines the application program that is to receive the packet (the destination). Another field defines the length of the entire packet. The last field carries a checksum for error detection.
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Figure 13-8TCP segment format
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Technical Focus:Technical Focus: Inside a TCP Segment HeaderInside a TCP Segment Header
The header of a segment is very complicated and contains optional as well as mandatory fields. We briefly discuss just the required fields. One pair of fields defines the source and destination application programs. Another pair is used for error and flow control; one holds the unique sequence number, and the other holds the acknowledgment number. One field defines the size of the sliding window in the transport layer. The sliding window in the transport layer uses the same concept as the one in the data link layer (see Chapter 5). There are also flags that define the purpose of the segment (for connection establishment, for termination, for acknowledgment, and so on). The last required field carries a checksum for error detection.
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NEXTNEXTGENERATIONGENERATION
NEXTNEXTGENERATIONGENERATION
13.313.3
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ACCESS TO THEACCESS TO THEINTERNETINTERNET
ACCESS TO THEACCESS TO THEINTERNETINTERNET
13.313.3
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PRIVATE NETWORKS:PRIVATE NETWORKS:INTRANET AND INTRANET AND
EXTRANETEXTRANET
PRIVATE NETWORKS:PRIVATE NETWORKS:INTRANET AND INTRANET AND
EXTRANETEXTRANET
13.513.5
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Technical Focus:Technical Focus: Network Address Translation (NAT)Network Address Translation (NAT)
A technology that is related to private networks is network address translation (NAT). The technology allows a site to use a set of private addresses for internal communication and a set of (at least one) global Internet addresses for communication with other sites.