Transport vs.network layer services and protocols -network layer:logical household analogy: communication between 12 kids in Ann's house sending letters to 12 kids in Bill's hosts house: transport layer:logical ■hosts=houses communication between ■processes=kids "app messages=letters in processes envelopes relies on,enhances,network layer services Transport Layer:3-6
Transport vs. network layer services and protocols ▪network layer: logical communication between hosts ▪transport layer: logical communication between processes • relies on, enhances, network layer services household analogy: 12 kids in Ann’s house sending letters to 12 kids in Bill’s house: ▪ hosts = houses ▪ processes = kids ▪ app messages = letters in envelopes ▪ transport protocol = Ann and Bill who demux to in-house siblings ▪ network-layer protocol = postal service Transport Layer: 3-6
Transport Layer Actions Sender: application is passed an application- ap app.msg layer message transport ■determines segment Th app.msg header fields values network(IP) ■creates segment network(IP) link passes segment to IP link physical physical Transport Layer:3-7
physical link network (IP) application physical link network (IP) application transport Transport Layer Actions Sender: ▪ is passed an application- app. msg layer message ▪ determines segment header fields values ▪ creates segment ▪ passes segment to IP transport TThh app. msg Transport Layer: 3-7
Transport Layer Actions Receiver: application receives segment from IP application 工 ■checks header values trapp.msg extracts application-layer transport message network(IP) demultiplexes message up network(IP) link to application via socket link nhysical physical Th app.msg Transport Layer:3-8
physical link network (IP) application physical link network (IP) application transport Transport Layer Actions transport Receiver: app. msg ▪ extracts application-layer message ▪ checks header values ▪ receives segment from IP Th app. msg ▪ demultiplexes message up to application via socket Transport Layer: 3-8
Two principal Internet transport protocols application transport TCP:Transmission Control Protocol mob network data link physica reliable,in-order delivery national or global ISP ·congestion control logica ·flow control 。connection setup local or -UDP:User Datagram Protocol regionalsp end-end transport unreliable,unordered delivery home network no-frills extension of "best-effort"IP appucation -services not available: transport network data link ·delay guarantees physical bandwidth guarantees enterprise network Transport Layer:3-9
Two principal Internet transport protocols mobile network home network enterprise network national or global ISP local or regional ISP datacenter network content provider network application transport network data link physical application transport network data link physical ▪TCP: Transmission Control Protocol • reliable, in-order delivery • congestion control • flow control • connection setup ▪UDP: User Datagram Protocol • unreliable, unordered delivery • no-frills extension of “best-effort” IP ▪ services not available: • delay guarantees • bandwidth guarantees Transport Layer: 3-9
Chapter 3:roadmap Transport-layer services -Multiplexing and demultiplexing Connectionless transport:UDP Principles of reliable data transfer Connection-oriented transport:TCP Principles of congestion control TCP congestion control Evolution of transport-layer functionality Transport Layer:3-10
Chapter 3: roadmap ▪ Transport-layer services ▪ Multiplexing and demultiplexing ▪ Connectionless transport: UDP ▪ Principles of reliable data transfer ▪ Connection-oriented transport: TCP ▪ Principles of congestion control ▪ TCP congestion control ▪ Evolution of transport-layer functionality Transport Layer: 3-10