Topic 1 composition of the Internet
1. Differences between early computers and modern computers
Early stage: Host-centric
Modern computers: Group-based exchange networks
2. The device connecting the network to the network is called a router.
3. From a macro perspective, the Internet can be divided into the edge part and the core part.
(1) edge part: composed of an end system (host)
Communication mode: the communication mode between hosts is C/S and P2P.
(2) Core part: it is composed of a group exchange network and a vro interconnected.
Role: Exchange data
Switching methods: circuit switching, group switching, and packet switching
4. View the internet structure from the ISP
(1) ISP: Network Service Provider
ISP at the first layer: Backbone Network (global)
ISP at the lowest layer: covering regional networks
(2) understanding important backbone networks in China
Topic 2 vro Exchange mode
1. Circuit switching:
Features:
(1) end-to-end communication is required
(2) exclusive line resources
Disadvantages: connection establishment takes a long time and resources are wasted. This is determined by the occasional nature of internet communication.
Advantages: reliable data and fast transmission
2. Circuit switching multiplexing technology (multiplexing and circuit switching)
Group exchange, because of high utilization, so there is no reuse
(1) frequency division multiplexing technology: divide different channels by frequency
Features: partially occupies the frequency and fully occupies the time
(2) time division multiplexing technology: divide different channels by time
Features: partially occupied time, fully occupied frequency
3. Group exchange technology: divides packets into multiple parts and adds header information.
Features: A connection is not established first, which is similar to packet exchange but unreliable.
Virtual Circuit: Analog circuit switching
(1) packet exchange: UDP protocol, no connection
(2) virtual circuit: TCP protocol, connection oriented
Topic 3 access technology
1. Dial-up Internet access, connected to a fixed telephone network, data exchange method: Circuit exchange
Access Device: Modem
2. ADSL, connected to a fixed telephone network
Access Device: separator. Separator function: frequency division multiplexing
3. Residential broadband: connected to the group Exchange Network
4. Residential access, device: cable modem
5. Network cable: Cross line: connect to the same device, Direct Line: connect to different devices
Topic 4
1. Bandwidth: the "highest data rate" that can be passed from one point in the network to another in a unit time"
Throughput: the amount of data actually transmitted through a network per unit time.
2. Throughput <= bandwidth
3. Factors affecting throughput are determined by small bandwidth.
End-to-end connection throughput = min (Rc, Rs, R/n)
4. Latency
Transmission latency, determined by the NIC
Propagation latency
Processing latency
Queue latency
Topic 5 network architecture
1. OSI/RM architecture, layer 5
TCP/IP architecture, layer-4
2. Master the TCP/IP system and the role of each layer
Application layer:
Transmission layer: multiplexing and sharing of network process data
Network layer: plan the transmission path
Data link layer: Data transmission
Topic 6 IP address
1. IP address: = {network number, host number}
2. Understand A, B, C, and 3 types of IP addresses
Address, subnet mask
A
0 network address 8-bit 255.0.0.0
B
10 network address 16-bit 255.255.0.0
C
110 network address 32-bit 255.255.255.0
3. The number of subnet masks 1, corresponding to the number of network numbers
From the host number, depending on the number of subnets
For example, 8 subnets, 2 ^ n-2> = 8
Full 1 and full 0 are not counted
4. Subnet mask & IP address = network number
5. The Gateway also belongs to the network.
Topic 7 DNS
1. Composition of host domain names
Access www.sohu.com
(1) top-level dns.com domain name server
(2) access the dns.sohu.com domain name server
Topic 8 Web
1. tcp protocol, divided into two types: non-persistent and persistent. Persistent protocols are divided into pipelines and non-pipelines.
2. Learn about cookie implementation.
3. web cache function: increases the speed of network access
Topic 9 ftp
Tcp connection, persistent connection two port numbers:
Theme 10 email server
1. Protocol for sending mail: SMTP
Protocol for reading emails: POP3 and IMAP
2. Understand the MIME protocol, MIME encoding QP, Base64
Topic 11 tcp
Understand the tcp header format
Computer Network (half-term review)
