Transmission medium
Coaxial cable:
Speeds up to 10 million per second, download speeds up to 1.25 million per second, the maximum effective transmission distance of 500 meters,
Fine coaxial cable:
The effective transmission distance of 185 meters,
B bit bit measure speed 1 b=8 b
B beit measure size/byte byte,
1 KB=1024=1024 * 8 b b
1 KB=1024 b
A bit binary number=1
Collision domains:
Definition: multiple devices on a Shared medium at the same time, the network to send data conflict happens, position of conflict is the collision domain
Collision domain solution: switch
Mitigation plan (CSMA/CD) carrier listen multiple access, conflict detection
1. Listen to the coma: listen, if there are electrical to wait, if not directly send data
2. Listen to side hair: equipment after sending data, should continue to listen line to see if there is other signals exist,
3. The conflict of hair: equipment after listen to line, if it is found that conflict is to stop sending data
4. Perform retreat algorithm: amplification conflict signal after the resignation of time step 1,
Simplex mode: equipment can only transmit or receive data, such as the radio duplex mode:
1. Half duplex
Devices can receive can also send, but you can't send at the same time, such as walkie-talkie
2. The full duplex
Devices can receive can also send, can simultaneously, such as the mobile computer
Protocol:
The OSI: open system interconnection
TCP/IP transmission control protocol (TCP) and Internet protocol
The OSI model
The application layer
The presentation layer
The session layer
The transport layer, transport layer)
The network layer (the layer)
The data link layer (layer network interface)
The physical layer
Application layer: provides an application access to the network interface
HTTP: hypertext transfer protocol
HTTPS: secure hypertext transfer protocol
FTP: file transfer protocol
TFTP: simple file transfer protocol
Telnet: remote agreement
SSH: safety remote agreement
SMTP/POP3: the simple mail transfer protocol, mail protocols,
DNS: DNS protocol,
The presentation layer:
Data encryption and decryption, and data format, data format conversion
The session layer: to establish a maintenance dismantle session connection
The session is the logical channel of data transmission between application
The transport layer (layer transport) : how end-to-end data transmission
TCP: transmission control protocol (TCP)
UDP: user packets agreement
Reliability:
TCP: reliable data will not happen damage or loss efficiency is low, in the event of damage or loss is the retransmission of data
UDP: no, reliable and efficient
Use location:
TCP: web pages, emails, tellet, mail transfer, FTP
UDP: suitable for real-time business data, telephone, video, live broadcast, the game
Network layer (the layer) of different network data transmission, providing addressing and selection, provide IP (Internet protocol)
IP:
1. Provide the IP address (only), is used to uniquely identifies a device in a network
The data link layer (layer network interface) : provide a physical address, realize the data communication between the same circuit devices, IEEE802.3, Ethernet lots, the PPP, in HDLC, FR
The PPP: point-to-point protocol
Ethernet, Ethernet protocol
In HDLC: high level data link control protocol (TCP)
FR: frame relay agreement
2. Provide the physical address, MAC address, the only global unique identification on a link in a device on a link in only effective
Agreed: the physical device interface type, the cable stitch, the pins of the interface and transmission speed and so on related content
TCP/IP:
Application layer: integration of OSI application, presentation and session produce need to pass data
Transport layer: application, transfer the data to the Great Wall, first of all, the data transport layer segmentation processing, convenient data transfer happen damage or loss retransmission
TCP transmission control protocol (TCP) features: connection-oriented, reliable transport service, low transmission efficiency, bandwidth
TCP - the Header (20 bytes) basic components: the head
A:
The source port: source port
Dstination port, destination port
Port range: 0 ~ 65350
Acknowledge Number: confirmation Number
The Header length, head length
Resv (sign) :
1. URG (emergency pointer)
2. An ACK (confirm)
3. PSH (push, push)
4. The RST (connection reset)
5. The SYN (synchronous)
6. FIN (end)
The Window size, Window size
The Check sum: inspection and (Check the data integrity)
2:
Extension head
Option
Padding
The working process:
Connection is established (three-way handshake) : use the SYN SYN/ACK, ACK connect
Reliable transmission: using the ACK message, serial number, confirm, and retransmission, achieve reliable transport
Flow control: control equipment based on sliding window mechanism is a send data quantity how much
Close the connection: based on the break up 4 times, use of FIN, ACK close connection,
UDP header (user data packet protocol)
The Source port: Source port
Destination port: Destination port
Length: the head and data size
The Check sum: Check and
Features:
The connection-oriented
Do your best to transmit data
High transmission efficiency, low bandwidth
Port: to distinguish the various service equipment, after receiving the data which applications or services delivered to the judge have a purpose port, the returned data source port and destination port to carry on the exchange,
Values of 0 ~ 65535 16 bit, 0 ~ 1024 for the well-known port number
HTTP 80
HTTPL 443
Telnet 23
SMTP 25
FTP 20,
DNS 53
Rip 520
IP packet header (20 ~ 60 b, basic and extended head head) :
Version (Version 4 values)
The Header Length (total Length)
ID (identification)
Flags (tag)
Fragment Offset (Offset)
Time To Live (TTL) survival Time for use with ring
Protocol (Protocol) is used to identify the upper data type
The Header CheckSum (Header CheckSum) is used to verify the integrity of the IP Header
IP address:
Network number: used to identify network address belong to
Main machine: used for within a network to distinguish the different equipment
The network address: used to represent a network, the host part of the whole 0
Broadcast address: for all the one-to-one communication within a network, all parts of the host 1
Subnet mask: the difference between the network part of the IP address and the host part of the
