CCNA Learning NOTE 1---OSI TCP/IP model

First, the actual application of the network classification

Block data streams: FTP, TFTP, inventory update

No direct human interaction required

Bandwidth is important, but not a critical factor

Interactive Data Flow: Inventory queries, database updates

Interactive

Response time

Facts app Data flow: VoIP video

People-to-people interaction

End-to-end latency is critical

Second, network topology classification

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At present, the actual is All Star type, the first two are only theoretical concepts

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Is the extended star type. Advantages: No center, distributed. High availability avoids a single point of failure resulting in network paralysis.

Iii. OSI layer Seven model

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Understand the process of end-to-end data transfer

Layered Advantages: 1, promote standardization work, allow the independent development of suppliers

2, each layer of independence, the network operation into a low-complexity thinking unit

3, flexibility, a layer of change will not affect the other layers

4, each layer through an interface in the adjacent layer up and down communication

Iv. TCP\IP Protocol Stack

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Data transfer top-down package transfer, peer-to-end received after solution encapsulation

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Indicates the last agreement. Layer Transport Layer: port number; Layer Network layer: TCP UDP; Layer Network access layer: IP (0800)

Each layer of the PDU (Protocol data Unit) communicates with each other using its own layer of protocols and each other's corresponding layers.

The information that the protocols in each layer interact at the peer level are called Protocol data units.

Upper---------------Message

Transport Layer-------------Segment

Network Layer-------------Packet

Data Link Layer---------frame

Physical layer-------------bit

Application Layer Overview: HTTP HTTPS

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Transport Layer

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TCP Encapsulation Format

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Common port number: FTP TCP21 file Transfer Protocol for uploading and downloading;

Telnet TCP23;

SMTP TCP25 Simple Mail Transfer Protocol;

DNS 53 Domain name Protocol, resolves the site name to an IP address, generally TCP server synchronization is UDP;

TFTP UDP69 Simple File Transfer Protocol;

SNMP UDP161; RIP UDP520

NTP UDP123 Network Time Protocol

RPC UDP111 Remote Procedure Call

UDP Encapsulation Format

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Network Layer Overview: IP

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IP Header Format IP protocol number 6->TCP;IP protocol number 17->UDP

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ICMP protocol

Level of understanding: according to the package classification: if understood as encapsulated on the IP layer 4

Classification by service object: Three Layer service is three layer ICMP for IP service so three tier

ICMP Check network is unblocked, divided into two categories: 1 difference message, 2 information class message

For example, ping belongs to information class messages. Trace route belongs to error message

CCNA Learning NOTE 1---OSI TCP/IP model