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PPP.1 CEENet 2000 - Understanding and using Remote Access and VPN services

PPPoEPPPoE(PPP over Ethernet)(PPP over Ethernet)

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Types of Point to PointTypes of Point to Point

ProtocolsProtocols

SLIP over async Very simple

IP only Unreliable - no checksum

HDLC over sync various proprietary versions

frames have checksum PPP

PPPoE

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PPPPPP

SLIP done right

Used for synchronous and asynchronous

transmission

Extended negotiation mechanism

Multiple protocol support

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PPPPPP

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PPP and OSI modelPPP and OSI model

Synchronous or Asynchronous Physical Media

LCP - LinkControl Protocol

PPP NetworkControl Protocol

IPCP IPXCP others

Physical Layer

Data LinkLayer

NetworkLayer

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LCPConfiguration OptionsLCPConfiguration Options

Feature Protocol

Authentication PAP,CH

APCompression Stacker, ..

ErrorDetection Quality

Multilink MPPP

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PAP/CHAPPAP/CHAP

PAP

Password required

Unencrypted password sent via the link

Allows storage of encrypted passwords

CHAP

Challenge handshake No passwords sent via the link

Need for storing unencrypted secrets

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Multilink PPPMultilink PPP

Combining physical links into one logicalbundle

Result: higher speed and lower latency

MPPP / Bonding

MPPP assembles/disassembles frames on theData LinkLayer

MPPP used for synchronous and asynchronousphysical links

Bonding assembles/disassembles on the bitlevel

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PPPoEPPPoE

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PPPoEPPPoE

PPP designed for serial communications

Now adapted to Ethernet called PPP over

Ethernet (PPPoE)

Since PPP was designed to do things that

were either impossible or unnecessary with

Ethernet, users are often confused as to whyone would want to use PPP over Ethernet at

all

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PPPoEPPPoE

Compare TCP/IP traffic to vehicle traffic

Basic TCP/IP protocol would be comparable to

a network of city streets

Streets can serve many access points

It is easy to get on to and off of the street

Additional access points can be added withlittle disruption

It is hard to tell how many cars are actually

using each street

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PPPoEPPPoE

PPP, on the other hand, would be

comparable to a railway

Travel is generally between two well definedpoints

You can't get on and off anywhere

It is relatively easy to count and monitorpassengers

You need a ticket to board.

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PPPoEPPPoE

If this is true, then isn't PPPoE like runningrailway tracks down main street?

In fact, yes, it is. That is what tramways do

Without disturbing main street traffic, theybring the advantages of railways

They offer speedy access between two welldefined points and allow you to count

passengers

And you need a ticket to board.

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PPPoEPPPoE

PPP over Ethernet brings this sort of

functionality to ISPs that do not use serial

links to connect their users Serial ISPs already use PPP over modem

communications

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PPPoEPPPoE

DSL providers on the other hand use

Ethernet, not serial communications

Because of this, many require the addedfunctionality of PPP over Ethernet, which

allows them to secure communications through

the use of user logins and have the ability to

measure the volume of traffic each usergenerates.

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PPPoEPPPoE

At this time the only users of PPPoE seem

to be DSl Internet Access Providers

Mostly Telcos and CLECS

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PPPoEPPPoE

DSL providers that require the use of

PPPoE generally supply software to their

subscribers This is fine if you are connecting a single

computer to the Internet via DSL

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PPPoEPPPoE

For users that connect an entire LAN to the

Internet via DSL, the software supplied by

the DSL provider may be insufficient There may be compatibility problems with the

router orInternet sharing software in use

between the LAN and the DSL connection

You will need to consult yourDSL provider

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PPPoEPPPoE

The PPoE standard requires that an

additional header be added to the beginning

of each TCP/IP packet This may cause the packet to become larger

than the maximum allowable size

Some software solutions handle thistransparently, but some require you to

modify the TCP/IP settings on all of the

client computers on the LAN

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PPPoEPPPoE

PPPoE over a LAN

Documents

pppoe 2