文档介绍：Chapter 9 UDP
Process-to-munication
User datagram
Checksum
UDP operation
Use of UDP
UDP package
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1
Transport Layer
Functions
To serve as the intermediary between the application programs and work operations
To create a process-to-munication
To provide a control mechanism at the transport layer
To provide a connection mechanism for the processes
Protocols
Transmission Control Protocol,TCP
User Datagram Protocol,UDP
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Process-to-m.
进程
Process
进程
Process
Domain of IP protocol
Domain of transport protocols
IP地址
协议端口(port)
端点(endpoint)
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Port Numbers
传输协议
Data
13
52000
Data
13
52000
传输协议
13
52000
客户
Client
服务器
Server
…
…
多目标
并发通信
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IP Address vs. Port Number
13
13
13
IP header
Transport
protocol
header
Port
number
IP
address
…
Choose
process
Choose
host
Transport
Layer
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IANA Ranges
Well-known ports
Assigned and controlled by IANA
Registered ports
Not assigned or controlled by IANA
Can only be registered with IANA to prevent duplication
Dynamic ports
Neither controlled nor registered
Can be used by any process
0
1023
1024
49151
49152
65535
Well-known
Registered
Dynamic
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Well-known Ports
ignments/port-numbers
The well-known Ports on most systems can only be used by system (or root) processes or by programs executed by privileged users
To the extent possible, some port assignments are both used with the TCP and UDP
Example:port 53(DNS)
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7
Socket Addresses
Generic structure
struct sockaddr {
short sa_family;
chat sa_data[14];
};
Address families
AF_LOCAL
……
DARPA style
struct sockaddr_in {
short sin_family;
unsigned short sin_port;
unsigned long sin_addr;
char sin_zero[8];
};
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8
User Datagram
User Datagram Protocol,UDP
RFC 768,用户数据报协议
IP
LANs
MANs
WANs
ICMP
IGMP
ARP
RARP
Network
Layer
Network
Access Layer
Application Layer
TCP
UDP
Transport
Layer
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9
IP header
IP