初级课程 Tcp Ip协议讲座2

Ethernet / TCP-IP - Training Suite

03 IP and UDP Protocols

2

TCP-IP : Key Protocols

Internet Layer

Transport Layer

Datalink Layer

I want to send data to 127.127.127.127

IP

IP

STM32F4x7

PHY

Eth

ern

et

IP

Internet Protocol

IP characteristic

IP header

IP Router

IP Packets Fragments

3

4

IP Characteristic Best Effort Delivery(unreliable, connectionless)

Packets can be lost Packets can be duplicated Packets can be received in any order

The IP protocol can fragment and rebuild fragmented packets

A

A C

A

B

Internet Protocol

IP Characteristic

IP Header

IP Router

IP Packets Fragments

5

6

Version(4) Hdr len(4) TOS(8) Total Length in bytes (16)

Identification (16 bits) Flags (3) Fragment Offset (13)

Time to Live (8) Protocol (8) Header Checksum (16)

Source IP Address

Destination IP Address

Options (if any)

Data (variable length)

Bit 0 Bit 31

Header

Data

IP Packet Header and Data

7




Source IP Address


Options (if any)

IP Packet Header

Version Version number of IP protocol (Version 4 or Version 6)

IP Packet Header

8




Source IP Address


Options (if any)

IP Packet Header

Header Length (in 32 bit words) Indicates end of header and beginning of payload If no options, Header length = 5 (5 * 32bytes)

IP Packet Header

9




Source IP Address


Options (if any)

IP Packet Header

Type of Service (TOS) Allows different types of service to be requested Initially, meaning was not well defined Currently being defined (different service)

IP Packet Header

10




Source IP Address


Options (if any)

IP Packet Header

Packet Length (in Bytes) Unambiguously specify end of packet Max packet size = 216 = 65,535 Bytes

IP Packet Header

11




Source IP Address


Options (if any)

IP Packet Header

These three fields for Fragmentation Control (will come back to them later)

IP Packet Header

12




Source IP Address


Options (if any)

IP Packet Header

Time to Live Initially set by sender (up to 255) Decremented by each router Discard when TTL = 0 to avoid infinite routing loops

IP Packet Header

13




Source IP Address


Options (if any)

IP Packet Header

Protocol Value indicates what is in the field Example: TCP, UDP, ICMP

IP Packet Header

14




Source IP Address


Options (if any)

IP Packet Header

Header Checksum Checks for error in the header only Bad header can harm the network If error found, packet is simply discarded

IP Packet Header

15




Source IP Address


Options (if any)

IP Packet Header

Source and Destination IP Address

IP Packet Header

16




Source IP Address


Options (if any)

IP Packet Header

Options Example: timestamp, record route, source route

IP Packet Header

Internet Protocol

IP Characteristic

IP Header

IP Router

IP Packets Fragments and Reassembly

17

IP Router

Router table (route)

Add: static, dynamic

RIP (Routing Information Protocol) UDP Port: 520

18

Internet Protocol

IP Characteristic

IP Header

IP Router

IP Packets Fragments and Reassembly

19

20

IP Fragmentation & Reassembly

Maximum Transmission Unit (MTU) Largest IP packet a network will accept Arriving IP packet may be larger (max IP packet size = 65,535 bytes)

Sender or router will split the packet into multiple fragments Destination will reassemble the packet IP header fields used to identify and order related fragments

IP Packet fragments and reassembly

21




Source IP Address


Options (if any)

IP Packet Header

Identification: All fragments of a single datagram have the same identification number

Flag: 1st bit: reserved, must be zero 2nd bit: DF -- Do not fragment 3rd bit: MF -- More fragments

Fragment Offset: Used for reassembly of packet 1st fragment has offset = 0

IP Packet Header

22

IP Fragments Example: IP fragments

23

TCP-IP : Key Protocols

Internet Layer

Transport Layer

Datalink Layer

I want to send a datagram on the port #

UDP

I want to send data to 127.127.127.127

IP

IP

UDP

STM32F4x7

PHY

Eth

ern

et

IP

UDP

UDP Characteristics

UDP does not provide :

Connections or logical circuits.

Flow control.

Retransmission of lost datagrams.

Acknowledgements of datagram reception.

It is a connectionless service.

24

25

User Datagram Protocol (UDP)

A very simple datagram service

Relies on the IP protocol

Advantages : simple, Lightweight

Drawbacks: A connectionless protocol (not reliable)

C

A

A

A

B

UDP Datagram Header and Data

Source port number (16bits) Destination port number (16bits)

UDP Length (16bits) UDP Checksum (16bits)

UDP Data

26

Source port

identifies the sending port Destination port

identifies the receiving port

Server port & Client port

Server port: must be assigned (snmp:80) Client port: assigned or random

UDP Datagram Header

Source port number (16bits) Destination port number (16bits)

UDP Length (16bits) UDP Checksum (16bits)

27

UDP Length Specifies the length in bytes of the UDP header and UDP data.

Checksum The checksum field is used for error-checking of the header and data. If

no checksum is generated by the transmitter, the field uses the value

all-zero. This field is not optional for IPv6.

The design of UDP server

The IP & port from client

The server can reply to any client request to it.

The destination IP

Sometimes the server need to know who the data want to sent to. (TFTP)

The UDP input queue

The server could endure the number of clients.

28

Ethernet / TCP-IP - Training Suite

03 - IP and UDP Protocols

初级课程 Tcp Ip协议讲座2

Documents