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1、Chapter 3 IP AddressesChapter 3 IP Addresses? ?IP address structureIP address structure? ?ClassfulClassful addressingaddressing? ?Special addressesSpecial addresses? ?Private addressesPrivate addresses? ?Sample InternetSample Internet? ?SubnettingSubnetting and maskand mask? ?SupernettingSupernettin
2、g? ?Classless addressingClassless addressing3.1 IPv43.1 IPv4? ?unreliableunreliable: there are no guarantees that an IP : there are no guarantees that an IP datagram successfully gets to its destination. IP datagram successfully gets to its destination. IP provides a best effort service. When someth
3、ing provides a best effort service. When something goes wrongs, such as a router temporarily goes wrongs, such as a router temporarily running out of buffers, IP has a simple error running out of buffers, IP has a simple error handling algorithm: throw away the datagram handling algorithm: throw awa
4、y the datagram and try to send an ICMP message back to the and try to send an ICMP message back to the source. Any required reliability must be provided source. Any required reliability must be provided by the upper layers (e.g., TCP) by the upper layers (e.g., TCP) ? ?ConnectionlessConnectionless:
5、IP does not maintain any state : IP does not maintain any state information about successive information about successive datagramsdatagrams. Each . Each datagram is handled independently from all datagram is handled independently from all other other datagramsdatagrams. This means that IP . This me
6、ans that IP datagramsdatagrams can get delivered out of order.can get delivered out of order.3.1.1 IP Address3.1.1 IP Address? ?IP addressIP address? ?A universal identifierA universal identifier? ?Uniquely defines a host or a router Uniquely defines a host or a router on the Interneton the Internet
7、? ?Host identifierHost identifier? ?NameName：what we seekwhat we seek? ?AddressAddress：where it iswhere it is? ?RouteRoute：how to get therehow to get there建设北路一环路建设北路一环路Network Network Network Network devicedevicedevicedeviceNetwork interfaceNetwork interfaceNetwork interfaceNetwork interfaceNetwork
8、 interfaceNetwork interfaceNetwork idNetwork id1 IP Address Structure1 IP Address Structure? ?3232- -bit binary addressbit binary address? ?Hierarchical addressingHierarchical addressing 32 bits32 bits32 bits32 bits Host idHost idIP Address IP Address PresentationPresentation? ?Decimal point notatio
9、nDecimal point notation（点分十进制）（点分十进制）8 bits8 bits8 bits8 bits10101100 00000110 01111010 1100110010101100 00000110 01111010 1100110010101100 00000110 01111010 1100110010101100 00000110 01111010 110011008 bits8 bits8 bits8 bits8 bits8 bits8 bits8 bits8 bits8 bits8 bits8 bits1721721721726 6 6 612212212
10、2122204204204204. . . . . . . . . .2 2 ClassfulClassful IPIP? ?Class AClass A? ?Class BClass B? ?Class CClass C? ?Class DClass D? ?Class EClass E1 1 1 1212121218 8 8 81 1 1 11 1 1 1bitsbitsbitsbits 1 11 11 11 10 00 0NetidNetidNetidNetidHostidHostidHostidHostid1 1 1 17 7 7 724242424bitsbitsbitsbits 0
11、 00 0NetidNetidNetidNetidHostidHostidHostidHostid1 1 1 114141414161616161 1 1 1bitsbitsbitsbits 1 11 10 00 0NetidNetidNetidNetidHostidHostidHostidHostid1 1 1 1282828281 1 1 11 1 1 1bitsbitsbitsbits 1 11 11 11 11 11 10 00 0MulticastMulticastMulticastMulticast1 1 1 128282828bitsbitsbitsbits 1 11 11 11
12、 11 11 11 11 1ReservedReservedReservedReserved1 1 1 1 1 1 1 11 1 1 11 1 1 10.0.0.0 127.255.255.2550.0.0.0 127.255.255.2550.0.0.0 127.255.255.2550.0.0.0 127.255.255.255128.0.0.0 191.255.255.255128.0.0.0 191.255.255.255128.0.0.0 191.255.255.255128.0.0.0 191.255.255.255192.0.0.0 223.255.255.255192.0.0.
13、0 223.255.255.255192.0.0.0 223.255.255.255192.0.0.0 223.255.255.255224.0.0.0 239.255.255.255224.0.0.0 239.255.255.255224.0.0.0 239.255.255.255224.0.0.0 239.255.255.255240.0.0.0 255.255.255.255240.0.0.0 255.255.255.255240.0.0.0 255.255.255.255240.0.0.0 255.255.255.255Net=2Net=2Net=2Net=27 7 7 7，Host=
14、2Host=2Host=2Host=224242424Net=2Net=2Net=2Net=214141414，Host=2Host=2Host=2Host=216161616Net=2Net=2Net=2Net=221212121，Host=2Host=2Host=2Host=28 8 8 8? ?Millions of class A address are wasted.Millions of class A address are wasted.? ?Many class B address are wasted.Many class B address are wasted.? ?T
15、he number of addresses in class C is smaller The number of addresses in class C is smaller than the needs of most organizations.than the needs of most organizations.? ?Class D address are used for multicasting; there Class D address are used for multicasting; there is only one block in this class.is
16、 only one block in this class.? ?Class E address are reserved for future purposes; Class E address are reserved for future purposes; most of the block is wasted.most of the block is wasted.3 Special Addresses3 Special AddressesSpecial AddressSpecial AddressNetidNetidHostidHostidSource or Source or DestinationDestinationNetwork addressNetwork addressSpecificSpecificAll 0sAll 0snonenoneDirect bro
