文档介绍：Transport Layer
3-*
Chapter 3: Transport Layer
Our goals:
understand principles behind transport layer services:
multiplexing/demultiplexing
reliable data transfer
flow control
congestion control
learn about transport layer protocols in the Internet:
UDP: connectionless transport
TCP: connection-oriented transport
TCP congestion control
Transport Layer
3-*
Chapter 3 outline
Transport-layer services
Multiplexing and demultiplexing
Connectionless transport: UDP
Principles of reliable data transfer
Connection-oriented transport: TCP
segment structure
reliable data transfer
flow control
connection management
Principles of congestion control
TCP congestion control
Transport Layer
3-*
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
more than one transport protocol available to apps
Internet: TCP and UDP
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
logical end-end transport
Transport Layer
3-*
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(gathering) and Bill(delivering)
network-layer protocol = postal service
Transport Layer
3-*
Internet transport-layer pr