Advanced network accounting notes (6)

Data link layer & LAN

service

Data from a point to an adjacent node in frames

• Framing
• Link access （ visit ） control
• Reliable data transmission between adjacent nodes （ For example, some wireless networks ）
• flow control
• Error detection / error correction
• full duplex / Half duplex

Node connection mode

• Point to point
  • Suitable for WAN
  • Networking is complex
  • The function of link layer is simple
• Multipoint connection
  • Suitable for LAN
  • Networking is convenient
  • But it needs to be solved MAC problem

Multiple access protocol MAC

The need for

The multipoint connection network coordinates the use of shared channels by each node

MAP

Channel division

• TDMA / FDMA / CDMA
• comprehensive TDMA & FDMA

Random access protocol RAP

• ALOHA / slotted ALOHA
• CSMA | CSMA/CD | CSMA/CA

Rotation agreement

token

Addressing

MAC Address

• Format ：48 Bit plane address , Identify the network card
• Distribute ：IEEE

And IP Address difference

• Different levels
• MAC Is a flat address , Identify different sites under the physical network
• IP Hierarchical , Aggregatable , Easy to calculate route

ARP agreement

Purpose

Within the physical network IP To MAC transformation

principle

Broadcast inquiry , Unicast response

Ethernet

IEEE802.3 standard , Links and corresponding physical layers

Frame structure

Leading dock department , The destination address is before

Service features

• There is no connection
• unreliable

Strong medium reliability , Unwanted

Access control technology

• CSMA/CD
• Index back

WLAN Access control technology

CSMA/CA

HUB

• Network layer devices , Signal shaping and amplification
• Single port in , All ports out , In the collision area
• Conflict free isolation

Switch

• SW Select forward
• Self learning ： Study MAC Bundled with the switch port
• Flow isolation ： Selective forwarding
• Dedicated access ： Port direct host

Router 3 layer
Switch 2 layer