11/22/

11/22/2013 2

Week3-4

What will you learn?

Representatives for

Point-to-Point Network

LAN

Wired Ethernet

Wireless Ethernet

WAN

IP model & its underlying

hardware network

P-to-P _{P-to-P WAN3 WAN3 LAN1 LAN1}

@home

@university

@ISP

Point-to-Point Network

Any direct connection between two computers

Dedicated line between two routers

Dialup connection (from telephone company)

On-demand basis, low speed

Leased line (from telephone company)

Permanent basis, High-speed

xDSL

Link-level protocol required for framing

PPP is popular

TCP/IP views as an independent physical network

Containing only 2 computers at the both end

Point-to-point network protocol

Most of point-to-point network uses PPP protocol

Link detection, authentication, framing

Layer 1 will be any selected link options providing

Direct bit transmission

Internet Internet PPP PPP P-to-P network P-to-P network Leased line, Dial-up, xDSL Leased line, Dial-up, xDSL Layer 2: framing

Layer 1: bit transmission

Layer 1’s modem

PPP protocol

PPP Frame Format

Local Area Network: Ethernet

Extremely popular

Can run over

Copper (twisted pair: UTP, STP)

Optical fiber (single mode, multi-mode)

wireless

IEEE standard is 802.x

Wired Ethernet (802.3)

Four generations

 10Base-T (Standard Ethernet)operates at 10 Mbps  100Base-T (Fast Ethernet) operates at 100 Mbps  1000Base-T (Gigabit Ethernet) operates at 1 Gbps  10 Gigabit Ethernet operates at 10 Gbps

Shared medium with MAC protocol=> CSMA/CD

Wireless Ethernet (802.11)

Ethernet network protocol

Layer 2 is divided into 2 sublayers

MAC => medium access method

Layer 1 will be Ethernet link options providing

Wired, wireless

Internet Internet

Ethernet network

Layer 2: framing, MAC Layer 1: bit transmission

Wired Ethernet (802.3) Frame

Format

Header format fixed (Destination, Source, Type fields)

Frame data size can vary from packet to packet

Maximum 1500 octets,
Minimum 46 Octets

Address is represented by Hexadecimal notation

Preamble, SFD and CRC removed by framer hardware (NIC) before

Example Ethernet Frame In Memory

Octet shown in hexadecimal

Destination is 02:07:01:00:27:ba

Changes in Standard Ethernet

Standard Ethernet => Bridged Ethernet =>

Switched Ethernet

Then, Fast Ethernet, Gigabit Ethernet,

Bridged Ethernet

Collision Domain => area in which collision may occur

Broadcasting Domain => area in which broadcast frame

propagates

Switched Ethernet

Implement dynamic bridge in which only a

computer at each port belongs to its own

collision domain

Fast Ethernet

Gigabit Ethernet

As 802.3z, for 1000 Mbps speed

10 Gigabit Ethernet

Extending LAN coverage

Using Repeater

Repeat all signals from

one LAN to the other

Ethernet HUB

Using Bridge

Selective repeat frames

from one LAN to the other

Selective repeat =>

based on frame’s

(hardware) address

Ethernet (Layer-2)

Collision & Broadcast Domain

HUB: same Collision & broadcast domain

VLAN implemented by L2-SW

VLAN => the LAN configured by software, not

IEEE 802.11

802.11 Extended Service Set

Protocol Stack of 802.11

PCF is optional protocol

(used by AP for time sensitive transmission

): Polling

MAC Frame Structure

Wide Area Network: ATM

Provide high-speed connection-oriented service (

switching technology

)

Each connection is identified by the assigned VPI/VCI

Each end point is identified by ATM address (come with ATM NIC)

Basic transferring packet is called “cell”

53 octets fixed size (5 octets for header)

User data will be divided by AAL method before being filled into ATM

ATM network protocol

Layer 3

AAL layer => data conversion

Layer 2 (OSI layer 3 function)

ATM layer => cell switching

Layer 1 will be high speed link options providing

Direct bit transmission
Mostly, optical fiber

Internet Internet ATM network ATM NIC ATM network Physical link options Physical link options AAL ATM AAL ATM Data conversion layer

ATM PHYPHY

ATM PHYPHY

Virtual Circuit –Switched Concept

A special type of packet switch

Connection establishment is needed

To reserve resource

Short (locally unique) value is assigned as one-time

address dynamically, it will last within this session=>

called “virtual connection (circuit) identifier”

Routing process is the same as packet switching,

excepting that it uses local one-time address (VCI)

Very fast routing

Connection release is needed

Virtual Circuit Switched (Con Request)

Need connection establishment to assign

Virtual Circuit Switched Model (con Ack)

Need connection establishment to assign

Virtual Circuit Switched (Transfer)

Need connection establishment to assign

ATM cell switching

ATM uses two-level virtual connection Identifier

ATM cell format

Between ATM swtich and

5 bytes

AAL5: Filling Data from computer

into ATM cell

ATM used in LAN

ATM switch will physically look like Ethernet

switch

Typical usage: LANE (LAN Emulation) software

P-to-P Special case: ADSL

Asymmetric Digital Subscriber line

Subscriber line

Copper wire (UTP3) from nearest telephone office to

your home

Called “local loop”, “subscriber loop” or “last mile”

Digital

Digital data or binary data

Asymmetric

Different data rates in uploading/downloading direction

Typical ADSL Point-to-point

system

Local loop (UTP3)

IP PPPoE Ethernet PPPoE Ethernet PPPoA ATM IP PPPoA ATM

PPPoE => PPP over Ethernet

• an extension of PPP defined how PPP frame is sent over Ethernet frame

PPPoA => PPP over ATM

ATM ATM ATM ATM

AAL5 AAL5

PPP PPP

ADSL System Architecture

@ home

• ADSL router: combined IP router+ ADSL modem @ Central office

ADSL Physical Layer

Shared UTP3 with telephone signal

Telephone signal (voice): 0-4KHz

ADSL signal

Upload: 26kHz-108kHz

Download: 138kHz-1104kHz

Splitter splits TEL & ADSL signal by low-pass & high-pass filter