1. Main protocols of application layer
(File Transfer Protocol) File transfer protocol reduces or eliminates the incompatibility of files processed under different operating systems.
Function: TFTP message does not provide user name and password.
The TFTP server uses UDP port 69.
Telnet
The purpose of Telnet protocol is to provide a relatively universal, bidirectional and byte-oriented communication method.
Working principle: Telnet remote login service actually takes the computer used by the user as the input terminal and the remote computer or remote host to be logged in as the host with fast processing ability.
This is a typical client/server structure, and the input/output interaction between client and server is realized through TCP connection.
Typical devices: processes and ports
Data unit: data segment
TCP (Transmission Control Protocol) provides reliable connection-oriented services. Before transmitting data, the connection must be established and then released. Reliable full duplex channel. Reliable, orderly, without loss and repetition.
UDP (User Datagram Protocol) does not need to establish a connection before sending data, does not use congestion control, does not guarantee reliable delivery, and tries its best to deliver data.
datagram congestion control protocol
Sctp (stream control transmission protocol) stream control transmission protocol.
RTP (Real-time Transport Protocol) Real-time transport protocol.
resource reservation protocol
PPTP (Point-to-Point Tunneling Protocol) Point-to-Point Tunneling Protocol.
Typical equipment: router, firewall, multilayer switch.
Data unit: package.
Ip (IPv4 IPv6) Internet Protocol (Network Interconnection Protocol)
ARP: Address resolution protocol, that is, address resolution protocol, which realizes knowing one's physical address through IP address.
RARP: reverse address resolution protocol. The reverse address translation protocol allows the physical machine of the local area network to request its IP address from the ARP table or cache of the gateway server.
Icmp: (Internet control message protocol) Internet control message protocol. It is a sub-protocol of TCP/IP protocol family, which is used to transfer control messages between IP hosts and routers.
* Address Resolution Protocol ARP* (Address Resolution Protocol)
* reverse address resolution protocol (rarp *)
* ICMP * (Internet Control Message Protocol)
* Internet Group Management Protocol IGMP * (Internet Group Management Protocol)
All IP datagrams sent from other networks to our company's host still find the router connected to our company's network according to the destination network number net-id of IP datagrams.
Then, after receiving the IP datagram, the router finds the destination subnet according to the destination network number net-id and subnet number subnet-id.
Finally, the IP datagram is directly transmitted to the destination host.
2) Type: static NAT, dynamic address NAT, NAPT.
1.ARP knows that IP is looking for MAC；; RARP, in turn.
2.ICMP allows hosts or routers to report errors and provide reports on abnormal situations.
3. The role of 3.ICMP is to improve the chances of successfully transmitting IP datagrams.
4. Names of four information messages and five error messages defined by 4.ICMP protocol.
Timeout (Timeout Message)
The goal cannot be achieved (the goal cannot be achieved)
Change route (redirect)
Request segmentation message
2) Information message: response request/response message.
The routing algorithm must be correct and complete;
The routing algorithm should be simple.
It should be adaptive.
It should be stable, fair and optimal.
1) discovers its neighbor nodes and knows its network address.
2) Measure the delay or overhead to its neighbor nodes.
3) Gather a group and tell it all the information it just knows.
4) Send this packet to all other routers.
5) Calculate the shortest path to other routers.
Internet Group Management Protocol (IGMP) is a multicast protocol in the Internet protocol family, which is used for IP hosts to report their group members to any directly adjacent router.
RIP is a standard for exchanging routing information between gateway and host.
Open the shortest path first. Open the shortest path first.
(intermediate system to intermediate system routing protocol) Routing protocol from intermediate system to intermediate system.
"Internet Protocol Security" is an open standard framework, which ensures the confidentiality and secure communication on the Internet Protocol (IP) network by using encrypted security services.
Border Gateway Protocol Border Gateway Protocol, a routing protocol for connecting independent systems on the Internet. Path vector routing protocol is adopted.
Typical equipment: network card, bridge and switch.
Data unit: frame
You can send data directly without establishing a connection first.
The data sent by Ethernet uses Manchester coded signal.
Carrier sense multiple access with collision detection.
PPP frame header (four fields) and trailer (two fields)
802.11.802.16 Wi-Fi WiMAX ATM DTM token ring Ethernet FDDI Frame Relay GPRS EVDO HspA HDLC PPP L2TP ISDN.
Serial line interface protocol
Typical equipment: repeaters, hubs, network cables and hubs.
Data unit: bits