IP addressing: CIDR Hierarchical addressing: route lassful addr Hierarchical addressing allows efficient advertisement e.g., class B net allocated enough addresses ts, even if only 2K hosts CIDR: Classless InterDomain Routing 20023180/23 network portion of address of arbitrary leng address format: a b c d/x, where x is bits in n of address 11001000000101110001000000000000 2m蓄 2002316,0/23 Hierarchical addressing: more specific routes IP datagram format ISPs-R-Us has a more specific route to Organization protocol vers 32 bits otal datagram length(bytes) augmentation/ begirt 20023200/23 FlyBy NghtIsF let d/ 32 bit source IP address Organiaton 32 bit destination IP address 20023,300/23 ISPs.RUs Organization IP v6- Version Number Why IPv6? (Theoretical Reasons) only compelling reason: more IP addresses IP v 1-3 defined and replaced for billions of new users(Japan, China, India,.) IP v4-current for billions of new devices(mobile phones, cars appliances…) IP for always-on access(cable, xDSL, ethernet-to-the IP v6-replacement for IP v4 for applications that are diff ensive. or During development it was called IPng impossible to operate through naTs(IP telephony. Next Generation peer-to-peer gaming home servers. to phase out NATs to improve the robustness, security, performance, and manageability of the Internet 1414 哈工大计算机学院 李全龙 Network Application Development 1: Introduction 79 IP addressing: CIDR „ classful addressing: „ inefficient use of address space, address space exhaustion „ e.g., class B net allocated enough addresses for 65K hosts, even if only 2K hosts in that network „ CIDR: Classless InterDomain Routing „ network portion of address of arbitrary length „ address format: a.b.c.d/x, where x is # bits in network portion of address 11001000 00010111 00010000 00000000 network part host part 200.23.16.0/23 哈工大计算机学院 李全龙 Network Application Development 1: Introduction 80 Hierarchical addressing: route aggregation “Send me anything with addresses beginning 200.23.16.0/20” 200.23.16.0/23 200.23.18.0/23 200.23.30.0/23 Fly-By-Night-ISP Organization 0 Organization 7 Internet Organization 1 ISPs-R-Us “Send me anything with addresses beginning 199.31.0.0/16” 200.23.20.0/23 Organization 2 . . . . . . Hierarchical addressing allows efficient advertisement of routing information: 哈工大计算机学院 李全龙 Network Application Development 1: Introduction 81 Hierarchical addressing: more specific routes ISPs-R-Us has a more specific route to Organization 1 “Send me anything with addresses beginning 200.23.16.0/20” 200.23.16.0/23 200.23.18.0/23 200.23.30.0/23 Fly-By-Night-ISP Organization 0 Organization 7 Internet Organization 1 ISPs-R-Us “Send me anything with addresses beginning 199.31.0.0/16 or 200.23.18.0/23” 200.23.20.0/23 Organization 2 . . . . . . 哈工大计算机学院 李全龙 Network Application Development 1: Introduction 82 IP datagram format Ver/4 Length/16 32 bits data (variable length, typically a TCP or UDP segment) 16-bit identifier Internet checksum/16 time to live/8 32 bit source IP address IP protocol version number header length (bytes) max number remaining hops (decremented at each router) for fragmentation/ reassembly total datagram length (bytes) upper layer protocol to deliver payload to head. len/4 type of service/8 “type” of data flgs/3 fragment offset/13 upper layer/8 32 bit destination IP address Options (if any) E.g. timestamp, record route taken, specify list of routers to visit. 哈工大计算机学院 李全龙 Network Application Development 1: Introduction 83 IP v6 - Version Number „ IP v 1-3 defined and replaced „ IP v4 - current version „ IP v5 - streams protocol „ IP v6 - replacement for IP v4 „ During development it was called IPng „ Next Generation 哈工大计算机学院 李全龙 Network Application Development 1: Introduction 84 Why IPv6?(Theoretical Reasons) only compelling reason: more IP addresses! „ for billions of new users (Japan, China, India,…) „ for billions of new devices (mobile phones, cars, appliances,…) „ for always-on access (cable, xDSL, ethernet-to-the￾home,…) „ for applications that are difficult, expensive, or impossible to operate through NATs (IP telephony, peer-to-peer gaming, home servers,…) „ to phase out NATs to improve the robustness, security, performance, and manageability of the Internet