Unit5_Trans - Transport Layer 5-1 Unit 5 Transport Layer...

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Unformatted text preview: Transport Layer 5-1 Unit 5 Transport Layer After studying this unit, you will be able to • explain the principles behind transport-layer services Transport Layer 5-2 Unit 5 outline ¡ 5.1 Transport-layer services ¡ 5.2 Multiplexing and Demultiplexing ¡ 5.3 Connectionless transport: UDP ¡ 5.4 Connection-oriented transport: TCP ¡ 5.5 Connection Management ¡ 5.6 Flow Control Transport Layer 5-3 Unit 5.1 Transport-Layer Services Transport Layer 5-4 Transport services and protocols ¡ provide logical communication between app processes running on different hosts ¡ transport protocols run in end systems ¢ send side: breaks app messages into segments , passes to network layer ¢ rcv side: reassembles segments into messages, passes to app layer application transport network data link physical application transport network data link physical network data link physical network data link physical network data link physical network data link physical network data link physical l o g i c a l e n d- e n d t r a n s p o r t Transport Layer 5-5 Processes communicating Process: program running within a host. ¡ within same host, two processes communicate using inter-process communication (defined by OS). ¡ processes in different hosts communicate by exchanging messages through a network. Client process: process that initiates communication Server process: process that waits to be contacted Transport Layer 5-6 Transport vs. network layer ¡ network layer: logical communication between hosts ¡ transport layer: logical communication between processes ¢ relies on, enhances, network layer services Household analogy: 12 kids sending letters to 12 kids ¡ processes = kids ¡ app messages = letters in envelopes ¡ hosts = houses ¡ transport protocol = Ann and Bill ¢ (kids of the two households responsible for mail collection and delivery.) ¡ network-layer protocol = postal service Transport Layer 5-7 Process-to-Process Communication Transport Layer 5-8 Comparisons ¡ Network Layer ¢ Service: host-to- host ¢ No choice: network provides one or the other • IP or other ¢ Implementation: in the core ¡ Transport Layer ¢ Service: process-to- process ¢ Choices available: applications can choose a suitable protocol • In the Internet, you can choose TCP or UDP. ¢ Implementation: in end-systems Transport Layer 5-9 Internet transport-layer protocols ¡ reliable, in-order delivery (TCP) ¢ congestion control ¢ flow control ¢ connection setup ¡ unreliable, unordered delivery: UDP ¢ simple extension of IP ¡ services not available in TCP/UDP: ¢ delay guarantees ¢ bandwidth guarantees application transport network data link physical application transport network data link physical network data link physical network data link physical network data link physical network data link physical network data link physical l o g i c a l e n d- e n d t r a n s p o r t Transport Layer 5-10 Connection Setup ¡ Before transmitting messages, two processes establish connection first.processes establish connection first....
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Unit5_Trans - Transport Layer 5-1 Unit 5 Transport Layer...

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