Addressing Addressing level(寻址级别 Addressing scope(寻址范围) Connection identifiers(连接表示符) Addressing mode(寻址方式) 1676
16/76 Addressing • Addressing level(寻址级别) • Addressing scope (寻址范围) • Connection identifiers (连接表示符) • Addressing mode (寻址方式)
TCP/IP Concepts Host A App x Port or App Y App service access point (S Logical connection TCP (TCP connection) TCP Global network P P Network Access Network Access Protocol #1 Protocol #2 Logical connection Physical Subnetwork attachment Physical point address Router j (e.g, virtual circuit) NAP 1 NAP 2 Network 1 Network 2 Physical Physical
17/76 TCP/IP Concepts
Addressing Level Level in comms architecture at which entity is named Unique address for each end system e.g. workstation or server And each intermediate system ( e.g., router) · Network- level address iP address or internet address OSl-network service access point(NSAP) Used to route PDu through network At destination data must routed to some process Each process assigned an identifier TCP/IP port Service access point (saP)in Os 18/76
18/76 Addressing Level • Level in comms architecture at which entity is named • Unique address for each end system - e.g. workstation or server • And each intermediate system - (e.g., router) • Network-level address - IP address or internet address - OSI - network service access point (NSAP) - Used to route PDU through network • At destination data must routed to some process - Each process assigned an identifier - TCP/IP port - Service access point (SAP) in OSI
Addressing Scope Global address Global nonambiguity(全局唯一) Identifies unique system Synonyms permitted许有同义字,系统可能有多个全局地址) Globa| applicability(全局适用性) Possible at any global address to identify any other global address, in any system, by means of global address of other system(通过使用系统中的的全局 地址,任何系统的全局地址都能被全局访问) Enables internet to route data between any two systems Need unique address for each device interface on network MAC address on iEEE 802 network and atm host address Enables network to route data units through network and deliver to intended system Network attachment point address Addressing scope only relevant for network- level addresses(地址的范围通常仅对网 络级地址而言是重要的) Port or SaP above network level is unique within system Need not be globally unique 1976
19/76 Addressing Scope • Global address - Global nonambiguity(全局唯一) - Identifies unique system - Synonyms permitted(允许有同义字，系统可能有多个全局地址) - Global applicability（全局适用性） - Possible at any global address to identify any other global address, in any system, by means of global address of other system（通过使用系统中的的全局 地址，任何系统的全局地址都能被全局访问) - Enables internet to route data between any two systems • Need unique address for each device interface on network - MAC address on IEEE 802 network and ATM host address - Enables network to route data units through network and deliver to intended system - Network attachment point address • Addressing scope only relevant for network-level addresses （地址的范围通常仅对网 络级地址而言是重要的） • Port or SAP above network level is unique within system - Need not be globally unique
Connection Identifiers Entity 1 on system A requests connection to entity 2 on system B, using global address B.2. B.2 accepts connection(通常是一个编号) Connection identifier used by both entities for future transmissions · Reduced overhead Generally shorter than global identifiers Routing Fixed route may be defined Connection identifier identifies route to intermediate systems Multiplexing Entity may wish more than one connection simultaneously PDUs must be identified by connection identifier Use of state information(连接有状态信息) Once connection established, end systems can maintain state information about connection Flow and error control using sequence numbers
20/76 Connection Identifiers • Entity 1 on system A requests connection to entity 2 on system B, using global address B.2. • B.2 accepts connection （通常是一个编号） • Connection identifier used by both entities for future transmissions • Reduced overhead - Generally shorter than global identifiers • Routing - Fixed route may be defined - Connection identifier identifies route to intermediate systems • Multiplexing - Entity may wish more than one connection simultaneously - PDUs must be identified by connection identifier • Use of state information(连接有状态信息) - Once connection established, end systems can maintain state information about connection - Flow and error control using sequence numbers