lecture 1 fundamentals: technology overview

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Lecture 1Fundamentals: Technology

Overview

Wireless Internet Protocols

Fundamentals: Technology Overview 2

Agenda

● Fundamentals of data networks● IP protocol suite● Introduction to addressing● Some basic tools for performance monitoring

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Fundamentals of Data Networks

●Circuit and packet switching●Protocols and layered architecture●The OSI model


Circuit Switching

● Stream of bits follows a path establishedduring call set-up

● Resources reserved for the duration of the call● Inefficient for exchange of data● Example: traditional telephone network

BackboneNetwork

Switches

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Packet Switching

● Data are sent in blocks: data + control information =a “packet”

● Resources not necessarily reserved in advance● Increased efficiency through statistical multiplexing● Example: the Internet

Backbonenetwork

Routers

Packets


Protocols

● Define the format and order of messages exchangedbetween two entities in the network

● Define the actions to be taken upon transmission orarrival of messages or some other event

● Examples: IP, HTTP, DHCP, etc.

Hello ! Hello !

Howare

you?

Fine,thanks!

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Layering

● Start with services provided by the hardware, thenadd a sequence of layers, each providing services tothe layer just above it

● Why?■ Decomposes the very complex problem of providing

networked communications into more manageable pieces■ More modular design (easier to add a new service or to

modify the functionality of a layer)

● Example of protocol layering■ HTTP (for web browsing) uses services from TCP (for

instance, reliable delivery of packets), which uses servicesprovided by IP (for instance, globally unique addressing)


OSI Model

Physical

Data link

Network

Transport

Session

Presentation

Application

End System

Voltage swing, bitduration, connectortype, etc.

Routing,segmentation andreassembly,network-wideaddressing

Addressing,medium access,error control

Reliable delivery,error recovery,congestion control

Application-specificexchange ofmessages

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Encapsulation

H2 H3 H4 M1 T2

H4H3 M1 H3 M2

H2 H3 M2 T2

H4 M

M

H2 H3 H4 M1 T2

H4H3 M1 H3 M2

H2 H3 M2 T2

H4 M

M

Layer 2Protocol

Layer 3Protocol

Layer 4 Protocol

Layer 5 Protocol

Layer 1 Protocol


IP basedInternet

The WWW

OtherServices

PSTN

Network

MPLS

Network

ATM

Network

Wireless

LAN

Modem, ADSL

VideoServer

Core Networks

Wireless

Network

Network Today

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Wireless Internet

New area■ Diverse mobile devices■ Wireless communication networks■ Internet■ Users can access various services, any time and any

where


BaseTransceiverStation (BTS)

Mobile ServiceSwitching Center(MSC)

PSTN, ISDN,PSPDN, CSPDN

Home LocationRegister, (HLR)

Visitor LocationRegister (VLR)

Mobile station(MS) with smartcard, SubscriberIdentity Module(SIM)

Equipment IDregister (EIR) andAuthenticationcenter (AuC)

cellular telephone system

Base StationController (BSC)

Base StationSubSystem

Network SubSystem

Architecture of GSM

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Architecture of GPRS

Mobile ServiceSwitching Center(MSC) Home Location

Register, (HLR)

Visitor LocationRegister (VLR)

GPRS Mobilestation (MS)

Equipment IDregister (EIR) andAuthenticationcenter (AuC)

Base StationController (BSC)

Serving GPRS supportnode, SGSN

Gateway GPRS supportnode, GGSN

IP andX.25

GR

GR: GPRS register,

a part of HLR


GPRS Mobile Station

● Three Classes■ Class A - simultaneous circuit switched (GSM) and packet

switched (GPRS) traffic■ Class B- supports both GSM and GPRS connections but

not both at the same time. One call is suspended for theduration of the other

■ Class C - handless both GPRS or GSM but can only beconnected to one at the same time

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GPRS Network Subsystem

● Two new nodes introduced for packet data■ Serving GPRS Support Node (SGSN)

○ monitors GPRS users○ handles security and access control○ may be regarded as the packet switched equivalent of the

circuit-switched MSC■ Gateway GPRS Support Node (GGSN)

○ internetworking functionality○ routes incoming data to correct SGSN○ translates between different protocols and formats

■


GPRSGeneral Packet Radio Service

WWW

GPRS tunnel ON IP

IPSec

● Forwards IP from mobile device to Internet or Intranet via GPRSbackbone network

IPSec

Logical link over RAN

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Third-GenerationMobile Communication System (3G)

● Frequency Band■ 1885~ 2025MHz and 2110~2200MHz

● Capable of providing high-speed data transmission● 384kbps for mobile; 2Mbps for stationary● Multimedia Service


3G, 2.5G and 2G

GSM/GPRS BTS

UMTS BTS

BSC MSC

RNC SGSN

GGSN

FixedTelephoneInfrastructure

PacketDataInfrastructure

Different radio access networks on the same core network

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Wireless LAN

● Replace the wired Ethernet LANs in a local area● Provide access to wired LANs and the Internet● Offer high data rates

■ Currently, up to 54 Mbps


Major Standards for WLAN

● HIPERLAN■ High Performance Radio LAN■ European standard

● IEEE 802.11■ US standard■ Today, it holds the entire market

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Two Modes of IEEE 802.11

● Infrastructure Mode■ Terminals communicate to an access point.

● Ad Hoc Mode■ Terminals communicate in a peer-to-peer basis without any

access point.


802.11 - Infrastructure Mode

APAP

Distribution System

Portal

Internet

Wired IEEE802.x LAN

IEEE 802.11 LAN

Basic Service Set(BSS) –thestations and APwithin the sameradio coverage.

BSS-1 BSS-2

Internetworking

Database forlocationmanagementand Roaming

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802.11 –Ad Hoc mode

Internet

Mobile Ad-hoc Networks(MANET)

● Ad-hoc On-demand Distance Vector (AODV)● Dynamic Source Routing (DSR)


● A layer 2 bridge between IEEE 802.11 andEthernet

● A switched Ethernet subnet attached tothe layer 2 distributed network

● A finite range, on the order of 500 feetindoor and 1000 feet outdoors

Access Point (AP)

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WLANterminals

WLANterminals

WLANRadio interface

AP

AP L2distributionnetworks

AccessRouter

AccessRouter

LocalService

IPbackbonenetwork

DNS DHCP

User DBL2distribution

network

Other WLAN APs

BillingSystem

HTTPserver

Gateway

AAAServer/Proxy

Interface toexternal IPnetworks(Internet)

AAAroaming

IP interface

WLAN, IP and Internet


Future of Wireless Networks

IP Backbone/Internet

Multi-mode terminalw/MobileIP client& IPSec Client

PublicWLAN

802.11 AccessPoints

Ethernet

WLANGateway

& FA

802.11 Access Points

Ethernet

WLANGateway,

HA, FA

Home AAA Server

Enterprise

Corporate LAN

VPNFirewall

PDSN/FA/HA/Firewall

CDMA WSP

PCF

BSBS

MSC/RNC

GGSN/FA/HA/Firewall

GSM/UMTSWSP

BS

BSC

SGSN

CGFBS

Mobile devices canconnect to office networksanytime from anywhere….

•Current mobility is based onsingle wireless technologies.

•Future will allow automaticconfiguration for seamlessroaming amongst variouswireless technologies…and,hence, greater coverage(ubiquitous).

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IP Protocol Suite

● IP stack●Basic characteristics and reasons for ubiquity of IP● ICMP


Why is IP so successful?

● Hourglass shape of the protocol stack■ Many protocols run “over”IP■ IP runs “over everything”

● Architectural principles■ Best effort service■ Stateless routers■ Decentralized control IP

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IP Protocol Stack

Application

Transport

Internet

Physical +Data Link

e.g. TELNET, FTP, SNMP, DNS,HTTP, etc.

TCP, UDP

IP

e.g. Ethernet, 802.11, SONET,ATM, etc.


OSI and the IP suite

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Essential Characteristics of IP

● Connectionless■ Each IP datagram is treated independently and may follow a

different path

● Best effort■ No guarantees of timely delivery, ordering, or even delivery

● Globally unique 32-bit addresses■ Usually expressed in dot-decimal notation: 128.17.75.0■ Each interface has its own IP address■ Later, we will see that there are ways to use non-unique

addresses

● Typical IP datagram contains payload + a 20-byteheader with control information (addressing,redundant bits for error detection, etc.)


Time to Live (TTL)

● IP datagram headers contain a TTL field■ At each router, this field is decremented; if it reaches 0,

datagram is discarded and an error message is generated

● Original purpose was to prevent datagrams fromendlessly circulating within the network

IP datagram(TTL=3)

TTL = 2TTL = 1

Error msg

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ICMP

● Internet Control Message Protocol (ICMP)■ Used by hosts, routers and gateways to communicate

network layer information to each other■ Typically used for error reporting

● Uses the services of IP■ ICMP messages are carried as IP payload

● ICMP messages have a type and code and containthe first 8 bytes of the IP datagram that caused theICMP message to be generated

● Many of the utilities we uses in daily life (ping,traceroute, etc.) are implemented by processingICMP messages


Introduction to Addressing

● IP addresses●MAC addresses●Address translation: DNS and ARP

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IP Addresses

● 32-bit addresses01001000 11000001 00000001 00001001

● Usually expressed in dot-decimal notation forconvenience

72 . 193 . 1 . 9


IP Address Assignment

Fixed IP address Dynamically-assigned IPaddress (using DHCP)

OR

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Address Translation: DNS

● From a domain name or URL (application layer) to anIP address (network layer)■ Use Domain Name System (DNS)■ Root and authoritative name servers provide the translation

between any possible domain name and an IP address■ Translation is cached locally


MAC addresses

● LAN adaptors have hard-coded Medium AccessControl (MAC) addresses

● These are 6-byte globally unique addresses■ First 3 bytes identify the vendor■ Expressed as hexadecimals separated by “:”

● Example:■ 02 : 60 : 8C : E4 : B1 : 02

3COM

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Address Translation: ARP

● From an IP address (network layer) to a MAC address(link layer)■ Use the Address Resolution Protocol (ARP)■ Results from an ARP query are kept locally in an ARP cache

ARP query: 111.111.111.111Source: 8B:B2:31:AA:1F:02Destination: FF:FF:FF:FF:FF:FF (broadcast)

ARP response: 8B:B2:31:B7:00:0FSource: 8B:B2:31:B7:00:0FDestination: 8B:B2:31:AA:1F:02

111.111.111.1128B:B2:31:AA:1F:02

111.111.111.1118B:B2:31:B7:00:0F

Some Basic Tools forPerformance Monitoring

● Ping● Traceroute● Ethereal

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Ping

● Measures the round-trip time (RTT) between twonodes

● Source node generates echo request(s), destinationnode responds with echo reply (replies)

Echo request(ICMP message)

Echo reply(ICMP message)


Ping Example

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Traceroute

● Lists all routers between source and destination● Send consecutive IP datagrams with TTL = 1, 2, …

■ Each of these will “die”at one of the intermediate routers,which will respond with an ICMP error message

■ Source will learn the identity of every router on the path

IP packetwith TTL=1

ICMP Time-to-LiveExceeded error message


Traceroute Example

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Ethereal

● A “GUI protocol analyzer”that display, organizes andfilters the results of packet sniffing

● A wide variety of packet types and protocols aresupported by Ethereal■ ATM, ARP, BGP, DNS, FTP, HTTP, IP, POP, TCP, UDP, and

many others (even Quake…)

● Each packet is shown with source, destination,protocol type, and comments■ A HEX dump shows you exactly what the packet looked like

as it went over the wire

● Many more features to be explored in the homework■ For more info, go to www.ethereal.com


Ethereal Example

TCP connection set up

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Observer

● Commercially-availablepacket sniffer

● Network monitor andprotocol analyzer forEthernet, Wireless802.11b/a/g, Token Ring andFDDI networks

● Vendor: NetworkInstruments

lecture 1 fundamentals: technology overview

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