ethernet principle issue 1.20

8/3/2019 Ethernet Principle ISSUE 1.20

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www.huawei.com

Copyright 2006 Huawei Technologies Co., Ltd. All rights reserved.

Ethernet Principle


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Page18Copyright 2006 Huawei Technologies Co., Ltd. All rights reserved.

Technical

StandardTypes of Cable

Transmission

Distance

100BaseTX 2 pairs EIA/TIA Type 5 (UTP) Unshielded Twisted Pair 100m

100BaseT4 4 pairs EIA/TIA Type 3, 4 and 5 (UTP) Unshielded Twisted Pair 100m

100BaseFX Multi-Mode Fiber (MMF) cable 550m-2km

1000BaseCX Copper shielded twisted-pair 25m

1000BaseT Copper EIA/TIA Category 5 (UTP) Unshielded twisted-pair, 4 pair 100m

1000BaseSX Multi-mode fiber, 50/62.5um fiber, use 850nm laser 550m/275m

EIA: Electronics Industries Association

TIA: Telecommunications Industries Association

Transmission Distance of Fast Ethernet


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If there is no auto-negotiation mechanism, the following

problems will arise:

Cannot realize the auto dual-rate configuration function of the

port (such as 10Mbit/s and 100Mbit/s)

Cannot confirm the operation mode of duplex Cannot confirm whether it's in need of the flow-control function

or not

If both of the equipment provide auto-negotiation then, it is

the best choice.

Ethernet Technology---Auto-

Negotiation


4/15Page20Copyright 2006 Huawei Technologies Co., Ltd. All rights reserved.

Fast link pulse includes a series of clock/digital

sequence comprised of link integration test pulse.

The basic mechanism of the auto-negotiation function is to

encapsulate the negotiation message into the link

integration test pulse.

16ms

Every pulse includes 16 digital sequence

Fast link pulse

Ethernet Technology---Auto-

Negotiation (Cont.)


5/15Page21Copyright 2006 Huawei Technologies Co., Ltd. All rights reserved.

Auto-Negotiation

If one device can not support auto-negotiation, the other device

that can support auto-negotiation will work at the default work

method.

Half-Duplex Full-Duplex

10M Support Support

100M Support Support

1000M - Support

10G - Support


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Auto-Negotiation on Optical Fiber

For the optical fiber Ethernet, the conclusion is:

The operation modes at two ends of the link must be manually

configured (speed, duplex modes, flow-control and etc.)

The auto-negotiation of Gigabit Ethernet has been realized


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Flow Control

The function of flow control is to prevent frames from being

lost in case of congestion

Under half duplex mode, the flow control is achieved by

backpressure technology

Under full duplex mode, the flow control generally abides by

standard IEEE 802.3x


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Half Duplex Flow Control

backpressure

Pretend that there iscollision, then you will notconstantly transfer!


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PAUSE Frame

DATA Frame

Full Duplex Flow Control

IEEE802.3x standard defines a new method named PAUSE

frame, to realize the flow control in the full duplex

environment.

PAUSE frame uses a reserved multicast address which

wouldn't be repeated by bridge or switch

Stop Congestion


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MAC VLAN

MAC A 5

10

5

10

MAC C

MAC B

MAC D

MAC A MAC B MAC C MAC D

Switch

Port VLAN

Port 1 5

10

5

10

Port 7

Port 3

Port 10

PC A PC B PC C PC D

Switch

Port 1

Port 3Port 7

Port 10

VLAN Based on MAC or Port


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Protocol VLAN

IPX 5

10

2

11

IP

UDP

.

IPX IP UDP IP

Switch

IP VLAN

1.1.1.1/24 5

10

2

11

1.1.3.1/24

1.1.2.1/24

.

1.1.1.1/24 1.1.2.1/24 1.1.3.1/24 2.1.1.1/24

Switch

VLAN Based on Protocol or Subnet


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Frame Format of VLAN

DA SA Type Data CRC

Standard Ethernet Frame

DA SA Type Data CRCtag

TPID Priority CFI VLAN ID

TCI

Ethernet Frame with IEEE802.IQ Flag


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VLAN 2 VLAN 1

VLAN 1 VLAN 2

Ethernet framewith VLAN tag 1

Ethernet framewith VLAN tag 2

Ethernet framewithout VLAN flag

Frame Changes in Network

Communication


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Ethernet Card Port Tag Mode

Packets

PortTag flag Untag flag

Tag aware (In) Transmit transparently

Transmit transparently

Drop

Remove the Tag flag (default

VLAN ID)

Transmit transparently

If VLAN ID is the same, remove

the Tag flag, otherwise transmit

transparently

Drop

Tag aware

(Out)

Access (In)Attach a Tag flag (default VLAN

ID)

Access (Out)

Hybrid (In)Attach a Tag flag (default VLAN

ID)

Hybrid (Out)


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Advantage and Disadvantage of VLAN

VLAN technology resolves the broadcast problem and

enhances the communication security.

Disadvantage of VLAN:

Improve the bandwidth utilization rate by dividing a physically

interconnected network into several small logic networks. But

what should we do if different VLANs need to communicate

with each other?

ethernet principle issue 1.20

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