1

ICS 101 Fall 2012 Networking and the Internet

Asst Prof Lipyeow LimInformation amp Computer Science Department

University of Hawaii at Manoa

942012 Lipyeow Lim -- University of Hawaii at Manoa

2

Problembull Ancient cities G and R have a made a pact that

each will come to the (military) aid of the other if one is in trouble

942012 Lipyeow Lim -- University of Hawaii at Manoa

AncientCity G Ancient

City R150 miles

G amp R are 150 miles apart How can they send a message for help

quickly

3

LOTR Beacon of Gondor

bull Video httpwwwyoutubecomwatchv=i6LGJ7evrAgbull Transmission medium air- line of sightbull Data encoding 1 bit ndash fire or no firebull All receivers have to be listeningbull Agreed upon interpretation of the signal at the endpointsbull Intermediate beacon wardens are always looking for a

signal and relaying the signalbull One way communication942012 Lipyeow Lim -- University of Hawaii at Manoa

Gondor Rohan150 miles

2

Problembull Ancient cities G and R have a made a pact that

each will come to the (military) aid of the other if one is in trouble

942012 Lipyeow Lim -- University of Hawaii at Manoa

AncientCity G Ancient

City R150 miles

G amp R are 150 miles apart How can they send a message for help

quickly

3

LOTR Beacon of Gondor

bull Video httpwwwyoutubecomwatchv=i6LGJ7evrAgbull Transmission medium air- line of sightbull Data encoding 1 bit ndash fire or no firebull All receivers have to be listeningbull Agreed upon interpretation of the signal at the endpointsbull Intermediate beacon wardens are always looking for a

signal and relaying the signalbull One way communication942012 Lipyeow Lim -- University of Hawaii at Manoa

Gondor Rohan150 miles

3

LOTR Beacon of Gondor

bull Video httpwwwyoutubecomwatchv=i6LGJ7evrAgbull Transmission medium air- line of sightbull Data encoding 1 bit ndash fire or no firebull All receivers have to be listeningbull Agreed upon interpretation of the signal at the endpointsbull Intermediate beacon wardens are always looking for a

signal and relaying the signalbull One way communication942012 Lipyeow Lim -- University of Hawaii at Manoa

Gondor Rohan150 miles

4

Modern Computer Networks

bull Signaling technology can transmit complex sequences of bits - packetsbull Each host or router obeys a set of rules for how to handle

incomingoutgoing messages ndash communication protocolsbull Communications can be multi-waybull Bandwidth the number of bits that can be transferred per second

(bps)bull Latency the time it takes for a message to reach the destination after

leaving the source

942012 Lipyeow Lim -- University of Hawaii at Manoa

Host computer

Host computer

Router Router Router

Fibre optic cables

Ethernet or WiFi

Host computer

Local area network

5

Local Area Networks

bull Wired (UTP Cat5) or Wireless 80211bull Connects hosts within a limited spatial region together to form

a networkbull All hosts within the network can ldquotalkrdquo to each otherbull The network is often a shared medium only one host can talk

at one time and the rest listens942012 Lipyeow Lim -- University of Hawaii at Manoa

6

Data Packetbull How messages are packaged for

delivery on the network ndash like postal mail

bull Source and destination addresses

942012 Lipyeow Lim -- University of Hawaii at Manoa

7

Network Abstractionsbull Network communications

are conceived as layers of abstractions

bull Each layer plays a specific role and is relatively independent of other layers

bull Each layer has its own packet format

bull Packets from higher layers are embedded in packets of lower layers ndash ldquoencapsulationrdquo

942012 Lipyeow Lim -- University of Hawaii at Manoa

Network

Application

Transport

Internet

Link

Application

Transport

Internet

Link

Application

Transport

Internet

Link

Physical Network

8

TCPIP Four Layer Model

942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

Link

bull Process to process communicates data to other processesapplications on the same host or on other hosts

bull Eg SMTP FTP SSH HTTP

bull Host to host communicates data to other host on the same network on on other networks

bull Hides the topology of the networkbull Flow control error correction connection controlbull Eg TCP UDP

bull Inter-network communicates data to other networksbull Deals with addressing and routing of datagrams to next

networkbull Eg IPv4 IPv6

bull Transmit data to other network interfaces on the local networkbull Eg Ethernet WiFi 80211

9

Link Layer

Data packet arrives from upper layer (Internet layer)bull If packet is too big break packet into smaller fragments (`framesrsquo)bull Embed data packet in a link layer packet with link layer header sequence

number error correction code etcbull Link layer packets gets transmitted on physical linkbull Link layer protocol governs how transmission over physical link is done Eg

Carrier sense multiple accessBottom-up process is similar on the receiving host

942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

Link

Application

Transport

Internet

Link

Physical Network

bull Eg Ethernet WiFi 80211bull A host can have multiple network interface

cards (eg Laptops typically have an ethernet interface and a WiFi interface)

bull Each interface has a 48-bit physical address that is hardwired to the hardware

10

Internet Layer

Data packet arrives from Transport layerbull Embed data packet in an IPv4 packet with IP header etcbull Pass packet to Link layer

Data packet arrives from Link layerbull Check IP header if packet destination is for this host If yes strip header and

pass to Transport layerbull Otherwise forward packet (routing)942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

Link

Application

Transport

Internet

Link

Physical Network

bull Eg IPv4bull Connects multiple networks togetherbull Each network interface of a host is

associated with an 32-bit IPv4 addressbull IP address is not hardwired but assigned in

the software

11

IPv4 Addresses amp Domain Name Service

bull IP addresses are 32 bit numbers often written in 4 octets 1281711013

bull Each address is also split into two partsndash Prefix is the network addressndash Suffix is the host address within that network

bull Domain Name Servers provide a service that translates more meaningful names to IP addressesndash Uhunixhawaiiedu = 12817124197ndash www2hawaiiedu = 128171224150

942012 Lipyeow Lim -- University of Hawaii at Manoa

128 171 10 13

Network Address Host Address

0 3116

12

IPv4 amp Inter-network Routing

For routersbull Examine destination IP addressbull Look up routing tables to determine outgoing networkbull Pass packet to link layer of that outgoing networkbull Best effort delivery ndash no guarantees

942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

LinkInternet

Link

Ethernet Network

Internet

Link

Application

Transport

Internet

Link

Ethernet NetworkFibre Network

host host

RouterRouter

13

Packet Routing Exercise

942012 Lipyeow Lim -- University of Hawaii at Manoa

14

Transport Layer

TCP provides a reliable communication channel between two host applications by addressing several issues

bull Data packets arriving out of orderbull Data packets are corruptedbull Same packets arriving more than oncebull Some packets are lostdiscardedbull Traffic congestion control

942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

Link

Application

Transport

Internet

Link

Physical Network

bull Eg TCP (connection-oriented) UDPbull End-to-end message transfer between

hosts applicationsbull Each application on a host is associated

with a port numberbull IP address + port number will identify an

application end-point

15

Applications Email

bull Your email client program downloads incoming emails from mail server (imapgmailcom popgmailcom)

bull Outgoing emails are sent to mail server (smtpgmailcom)bull Mail servers handle the routing of emails using SMTP protocol which

operates on port 25 or 587ndash Lookup IP address of destination hostname in the email address using DNSndash Relaying email as packets to that IP address

942012 Lipyeow Lim -- University of Hawaii at Manoa

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

Network

Mail Server Mail Server

Network Internet

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

Mail Client Mail Client

16

Sample Email HeaderDelivered-To strevguhrelayhawaiieduReceived by 10581456 with SMTP id sq6csp687725veb

Mon 3 Sep 2012203901 -0700 (PDT)Received by 106812938 with SMTP id

nt6mr43102232pbb761346729940698 Mon03 Sep 2012 203900 -0700 (PDT)Return-Path ltpostmasterlaulimahawaiiedugtReceived from mta11itshawaiiedu (mta11itshawaiiedu

[128171224147])by mxgooglecom with ESMTPS id

px6si25354378pbc21420120903203853(version=TLSv1SSLv3 cipher=RC4-MD5) Mon 03 Sep 2012

203900 -0700 (PDT)Received-SPF pass (googlecom domain of

postmasterlaulimahawaiiedudesignates 12817122458 as permitted sender) client-ip=

12817122458Authentication-Results mxgooglecom spf=pass (googlecom

domain ofpostmasterlaulimahawaiiedu designates 12817122458

as permitted sender)smtpmail=postmasterlaulimahawaiieduMIME-version 10Content-type multipartmixed

boundary=Boundary_(ID_3RY8N2VbJHb4tH5siR1eww)

Received from pmx11itshawaiiedu (pmx11itshawaiiedu [12817122458]) by

mta11itshawaiiedu (Sun Java(tm) System Messaging Server 63-1101 (built

Feb 12 2010 32bit)) with ESMTP id lt0M9T0071I3GJ4F40mta11itshawaiiedugt

Mon 03 Sep 2012 173845 -1000 (HST)Received from kuhiitshawaiiedu (kuhiitshawaiiedu

[12817125223]) bypmx11itshawaiiedu (Postfix) with ESMTP id E587118C023

Mon 03 Sep 2012173842 -1000 (HST)Received from sak24itshawaiiedu (sak24itshawaiiedu

[128171225199])by kuhiitshawaiiedu (812108126) with ESMTP id

q843ccvH023430 Mon 03Sep 2012 173838 -1000 (HST)Date Mon 03 Sep 2012 173833 -1000 (HST)From Dennis Streveler ltstrevhawaiiedugtCc strevhawaiiedu ltstrevhawaiiedugtMessage-id lt

11298755423101346729913602JavaMailsakaisak24itshawaiiedugt

Subject ICS 101 Help Tuesday lecture -- Everything you THOUGHT you knew

about NETWORKS and then someX-Mailer sakai-mailsender

942012 Lipyeow Lim -- University of Hawaii at Manoa

5

Local Area Networks

bull Wired (UTP Cat5) or Wireless 80211bull Connects hosts within a limited spatial region together to form

a networkbull All hosts within the network can ldquotalkrdquo to each otherbull The network is often a shared medium only one host can talk

at one time and the rest listens942012 Lipyeow Lim -- University of Hawaii at Manoa

6

Data Packetbull How messages are packaged for

delivery on the network ndash like postal mail

bull Source and destination addresses

942012 Lipyeow Lim -- University of Hawaii at Manoa

7

Network Abstractionsbull Network communications

are conceived as layers of abstractions

bull Each layer plays a specific role and is relatively independent of other layers

bull Each layer has its own packet format

bull Packets from higher layers are embedded in packets of lower layers ndash ldquoencapsulationrdquo

942012 Lipyeow Lim -- University of Hawaii at Manoa

Network

Application

Transport

Internet

Link

Application

Transport

Internet

Link

Application

Transport

Internet

Link

Physical Network

8

TCPIP Four Layer Model

942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

Link

bull Process to process communicates data to other processesapplications on the same host or on other hosts

bull Eg SMTP FTP SSH HTTP

bull Host to host communicates data to other host on the same network on on other networks

bull Hides the topology of the networkbull Flow control error correction connection controlbull Eg TCP UDP

bull Inter-network communicates data to other networksbull Deals with addressing and routing of datagrams to next

networkbull Eg IPv4 IPv6

bull Transmit data to other network interfaces on the local networkbull Eg Ethernet WiFi 80211

9

Link Layer

Data packet arrives from upper layer (Internet layer)bull If packet is too big break packet into smaller fragments (`framesrsquo)bull Embed data packet in a link layer packet with link layer header sequence

number error correction code etcbull Link layer packets gets transmitted on physical linkbull Link layer protocol governs how transmission over physical link is done Eg

Carrier sense multiple accessBottom-up process is similar on the receiving host

942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

Link

Application

Transport

Internet

Link

Physical Network

bull Eg Ethernet WiFi 80211bull A host can have multiple network interface

cards (eg Laptops typically have an ethernet interface and a WiFi interface)

bull Each interface has a 48-bit physical address that is hardwired to the hardware

10

Internet Layer

Data packet arrives from Transport layerbull Embed data packet in an IPv4 packet with IP header etcbull Pass packet to Link layer

Data packet arrives from Link layerbull Check IP header if packet destination is for this host If yes strip header and

pass to Transport layerbull Otherwise forward packet (routing)942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

Link

Application

Transport

Internet

Link

Physical Network

bull Eg IPv4bull Connects multiple networks togetherbull Each network interface of a host is

associated with an 32-bit IPv4 addressbull IP address is not hardwired but assigned in

the software

11

IPv4 Addresses amp Domain Name Service

bull IP addresses are 32 bit numbers often written in 4 octets 1281711013

bull Each address is also split into two partsndash Prefix is the network addressndash Suffix is the host address within that network

bull Domain Name Servers provide a service that translates more meaningful names to IP addressesndash Uhunixhawaiiedu = 12817124197ndash www2hawaiiedu = 128171224150

942012 Lipyeow Lim -- University of Hawaii at Manoa

128 171 10 13

Network Address Host Address

0 3116

12

IPv4 amp Inter-network Routing

For routersbull Examine destination IP addressbull Look up routing tables to determine outgoing networkbull Pass packet to link layer of that outgoing networkbull Best effort delivery ndash no guarantees

942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

LinkInternet

Link

Ethernet Network

Internet

Link

Application

Transport

Internet

Link

Ethernet NetworkFibre Network

host host

RouterRouter

13

Packet Routing Exercise

942012 Lipyeow Lim -- University of Hawaii at Manoa

14

Transport Layer

TCP provides a reliable communication channel between two host applications by addressing several issues

bull Data packets arriving out of orderbull Data packets are corruptedbull Same packets arriving more than oncebull Some packets are lostdiscardedbull Traffic congestion control

942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

Link

Application

Transport

Internet

Link

Physical Network

bull Eg TCP (connection-oriented) UDPbull End-to-end message transfer between

hosts applicationsbull Each application on a host is associated

with a port numberbull IP address + port number will identify an

application end-point

15

Applications Email

bull Your email client program downloads incoming emails from mail server (imapgmailcom popgmailcom)

bull Outgoing emails are sent to mail server (smtpgmailcom)bull Mail servers handle the routing of emails using SMTP protocol which

operates on port 25 or 587ndash Lookup IP address of destination hostname in the email address using DNSndash Relaying email as packets to that IP address

942012 Lipyeow Lim -- University of Hawaii at Manoa

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

Network

Mail Server Mail Server

Network Internet

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

Mail Client Mail Client

16

Sample Email HeaderDelivered-To strevguhrelayhawaiieduReceived by 10581456 with SMTP id sq6csp687725veb

Mon 3 Sep 2012203901 -0700 (PDT)Received by 106812938 with SMTP id

nt6mr43102232pbb761346729940698 Mon03 Sep 2012 203900 -0700 (PDT)Return-Path ltpostmasterlaulimahawaiiedugtReceived from mta11itshawaiiedu (mta11itshawaiiedu

[128171224147])by mxgooglecom with ESMTPS id

px6si25354378pbc21420120903203853(version=TLSv1SSLv3 cipher=RC4-MD5) Mon 03 Sep 2012

203900 -0700 (PDT)Received-SPF pass (googlecom domain of

postmasterlaulimahawaiiedudesignates 12817122458 as permitted sender) client-ip=

12817122458Authentication-Results mxgooglecom spf=pass (googlecom

domain ofpostmasterlaulimahawaiiedu designates 12817122458

as permitted sender)smtpmail=postmasterlaulimahawaiieduMIME-version 10Content-type multipartmixed

boundary=Boundary_(ID_3RY8N2VbJHb4tH5siR1eww)

Received from pmx11itshawaiiedu (pmx11itshawaiiedu [12817122458]) by

mta11itshawaiiedu (Sun Java(tm) System Messaging Server 63-1101 (built

Feb 12 2010 32bit)) with ESMTP id lt0M9T0071I3GJ4F40mta11itshawaiiedugt

Mon 03 Sep 2012 173845 -1000 (HST)Received from kuhiitshawaiiedu (kuhiitshawaiiedu

[12817125223]) bypmx11itshawaiiedu (Postfix) with ESMTP id E587118C023

Mon 03 Sep 2012173842 -1000 (HST)Received from sak24itshawaiiedu (sak24itshawaiiedu

[128171225199])by kuhiitshawaiiedu (812108126) with ESMTP id

q843ccvH023430 Mon 03Sep 2012 173838 -1000 (HST)Date Mon 03 Sep 2012 173833 -1000 (HST)From Dennis Streveler ltstrevhawaiiedugtCc strevhawaiiedu ltstrevhawaiiedugtMessage-id lt

11298755423101346729913602JavaMailsakaisak24itshawaiiedugt

Subject ICS 101 Help Tuesday lecture -- Everything you THOUGHT you knew

about NETWORKS and then someX-Mailer sakai-mailsender

942012 Lipyeow Lim -- University of Hawaii at Manoa

6

Data Packetbull How messages are packaged for

delivery on the network ndash like postal mail

bull Source and destination addresses

942012 Lipyeow Lim -- University of Hawaii at Manoa

7

Network Abstractionsbull Network communications

are conceived as layers of abstractions

bull Each layer plays a specific role and is relatively independent of other layers

bull Each layer has its own packet format

bull Packets from higher layers are embedded in packets of lower layers ndash ldquoencapsulationrdquo

942012 Lipyeow Lim -- University of Hawaii at Manoa

Network

Application

Transport

Internet

Link

Application

Transport

Internet

Link

Application

Transport

Internet

Link

Physical Network

8

TCPIP Four Layer Model

942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

Link

bull Process to process communicates data to other processesapplications on the same host or on other hosts

bull Eg SMTP FTP SSH HTTP

bull Host to host communicates data to other host on the same network on on other networks

bull Hides the topology of the networkbull Flow control error correction connection controlbull Eg TCP UDP

bull Inter-network communicates data to other networksbull Deals with addressing and routing of datagrams to next

networkbull Eg IPv4 IPv6

bull Transmit data to other network interfaces on the local networkbull Eg Ethernet WiFi 80211

9

Link Layer

Data packet arrives from upper layer (Internet layer)bull If packet is too big break packet into smaller fragments (`framesrsquo)bull Embed data packet in a link layer packet with link layer header sequence

number error correction code etcbull Link layer packets gets transmitted on physical linkbull Link layer protocol governs how transmission over physical link is done Eg

Carrier sense multiple accessBottom-up process is similar on the receiving host

942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

Link

Application

Transport

Internet

Link

Physical Network

bull Eg Ethernet WiFi 80211bull A host can have multiple network interface

cards (eg Laptops typically have an ethernet interface and a WiFi interface)

bull Each interface has a 48-bit physical address that is hardwired to the hardware

10

Internet Layer

Data packet arrives from Transport layerbull Embed data packet in an IPv4 packet with IP header etcbull Pass packet to Link layer

Data packet arrives from Link layerbull Check IP header if packet destination is for this host If yes strip header and

pass to Transport layerbull Otherwise forward packet (routing)942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

Link

Application

Transport

Internet

Link

Physical Network

bull Eg IPv4bull Connects multiple networks togetherbull Each network interface of a host is

associated with an 32-bit IPv4 addressbull IP address is not hardwired but assigned in

the software

11

IPv4 Addresses amp Domain Name Service

bull IP addresses are 32 bit numbers often written in 4 octets 1281711013

bull Each address is also split into two partsndash Prefix is the network addressndash Suffix is the host address within that network

bull Domain Name Servers provide a service that translates more meaningful names to IP addressesndash Uhunixhawaiiedu = 12817124197ndash www2hawaiiedu = 128171224150

942012 Lipyeow Lim -- University of Hawaii at Manoa

128 171 10 13

Network Address Host Address

0 3116

12

IPv4 amp Inter-network Routing

For routersbull Examine destination IP addressbull Look up routing tables to determine outgoing networkbull Pass packet to link layer of that outgoing networkbull Best effort delivery ndash no guarantees

942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

LinkInternet

Link

Ethernet Network

Internet

Link

Application

Transport

Internet

Link

Ethernet NetworkFibre Network

host host

RouterRouter

13

Packet Routing Exercise

942012 Lipyeow Lim -- University of Hawaii at Manoa

14

Transport Layer

TCP provides a reliable communication channel between two host applications by addressing several issues

bull Data packets arriving out of orderbull Data packets are corruptedbull Same packets arriving more than oncebull Some packets are lostdiscardedbull Traffic congestion control

942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

Link

Application

Transport

Internet

Link

Physical Network

bull Eg TCP (connection-oriented) UDPbull End-to-end message transfer between

hosts applicationsbull Each application on a host is associated

with a port numberbull IP address + port number will identify an

application end-point

15

Applications Email

bull Your email client program downloads incoming emails from mail server (imapgmailcom popgmailcom)

bull Outgoing emails are sent to mail server (smtpgmailcom)bull Mail servers handle the routing of emails using SMTP protocol which

operates on port 25 or 587ndash Lookup IP address of destination hostname in the email address using DNSndash Relaying email as packets to that IP address

942012 Lipyeow Lim -- University of Hawaii at Manoa

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

Network

Mail Server Mail Server

Network Internet

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

Mail Client Mail Client

16

Sample Email HeaderDelivered-To strevguhrelayhawaiieduReceived by 10581456 with SMTP id sq6csp687725veb

Mon 3 Sep 2012203901 -0700 (PDT)Received by 106812938 with SMTP id

nt6mr43102232pbb761346729940698 Mon03 Sep 2012 203900 -0700 (PDT)Return-Path ltpostmasterlaulimahawaiiedugtReceived from mta11itshawaiiedu (mta11itshawaiiedu

[128171224147])by mxgooglecom with ESMTPS id

px6si25354378pbc21420120903203853(version=TLSv1SSLv3 cipher=RC4-MD5) Mon 03 Sep 2012

203900 -0700 (PDT)Received-SPF pass (googlecom domain of

postmasterlaulimahawaiiedudesignates 12817122458 as permitted sender) client-ip=

12817122458Authentication-Results mxgooglecom spf=pass (googlecom

domain ofpostmasterlaulimahawaiiedu designates 12817122458

as permitted sender)smtpmail=postmasterlaulimahawaiieduMIME-version 10Content-type multipartmixed

boundary=Boundary_(ID_3RY8N2VbJHb4tH5siR1eww)

Received from pmx11itshawaiiedu (pmx11itshawaiiedu [12817122458]) by

mta11itshawaiiedu (Sun Java(tm) System Messaging Server 63-1101 (built

Feb 12 2010 32bit)) with ESMTP id lt0M9T0071I3GJ4F40mta11itshawaiiedugt

Mon 03 Sep 2012 173845 -1000 (HST)Received from kuhiitshawaiiedu (kuhiitshawaiiedu

[12817125223]) bypmx11itshawaiiedu (Postfix) with ESMTP id E587118C023

Mon 03 Sep 2012173842 -1000 (HST)Received from sak24itshawaiiedu (sak24itshawaiiedu

[128171225199])by kuhiitshawaiiedu (812108126) with ESMTP id

q843ccvH023430 Mon 03Sep 2012 173838 -1000 (HST)Date Mon 03 Sep 2012 173833 -1000 (HST)From Dennis Streveler ltstrevhawaiiedugtCc strevhawaiiedu ltstrevhawaiiedugtMessage-id lt

11298755423101346729913602JavaMailsakaisak24itshawaiiedugt

Subject ICS 101 Help Tuesday lecture -- Everything you THOUGHT you knew

about NETWORKS and then someX-Mailer sakai-mailsender

942012 Lipyeow Lim -- University of Hawaii at Manoa

7

Network Abstractionsbull Network communications

are conceived as layers of abstractions

bull Each layer plays a specific role and is relatively independent of other layers

bull Each layer has its own packet format

bull Packets from higher layers are embedded in packets of lower layers ndash ldquoencapsulationrdquo

942012 Lipyeow Lim -- University of Hawaii at Manoa

Network

Application

Transport

Internet

Link

Application

Transport

Internet

Link

Application

Transport

Internet

Link

Physical Network

8

TCPIP Four Layer Model

942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

Link

bull Process to process communicates data to other processesapplications on the same host or on other hosts

bull Eg SMTP FTP SSH HTTP

bull Host to host communicates data to other host on the same network on on other networks

bull Hides the topology of the networkbull Flow control error correction connection controlbull Eg TCP UDP

bull Inter-network communicates data to other networksbull Deals with addressing and routing of datagrams to next

networkbull Eg IPv4 IPv6

bull Transmit data to other network interfaces on the local networkbull Eg Ethernet WiFi 80211

9

Link Layer

Data packet arrives from upper layer (Internet layer)bull If packet is too big break packet into smaller fragments (`framesrsquo)bull Embed data packet in a link layer packet with link layer header sequence

number error correction code etcbull Link layer packets gets transmitted on physical linkbull Link layer protocol governs how transmission over physical link is done Eg

Carrier sense multiple accessBottom-up process is similar on the receiving host

942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

Link

Application

Transport

Internet

Link

Physical Network

bull Eg Ethernet WiFi 80211bull A host can have multiple network interface

cards (eg Laptops typically have an ethernet interface and a WiFi interface)

bull Each interface has a 48-bit physical address that is hardwired to the hardware

10

Internet Layer

Data packet arrives from Transport layerbull Embed data packet in an IPv4 packet with IP header etcbull Pass packet to Link layer

Data packet arrives from Link layerbull Check IP header if packet destination is for this host If yes strip header and

pass to Transport layerbull Otherwise forward packet (routing)942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

Link

Application

Transport

Internet

Link

Physical Network

bull Eg IPv4bull Connects multiple networks togetherbull Each network interface of a host is

associated with an 32-bit IPv4 addressbull IP address is not hardwired but assigned in

the software

11

IPv4 Addresses amp Domain Name Service

bull IP addresses are 32 bit numbers often written in 4 octets 1281711013

bull Each address is also split into two partsndash Prefix is the network addressndash Suffix is the host address within that network

bull Domain Name Servers provide a service that translates more meaningful names to IP addressesndash Uhunixhawaiiedu = 12817124197ndash www2hawaiiedu = 128171224150

942012 Lipyeow Lim -- University of Hawaii at Manoa

128 171 10 13

Network Address Host Address

0 3116

12

IPv4 amp Inter-network Routing

For routersbull Examine destination IP addressbull Look up routing tables to determine outgoing networkbull Pass packet to link layer of that outgoing networkbull Best effort delivery ndash no guarantees

942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

LinkInternet

Link

Ethernet Network

Internet

Link

Application

Transport

Internet

Link

Ethernet NetworkFibre Network

host host

RouterRouter

13

Packet Routing Exercise

942012 Lipyeow Lim -- University of Hawaii at Manoa

14

Transport Layer

TCP provides a reliable communication channel between two host applications by addressing several issues

bull Data packets arriving out of orderbull Data packets are corruptedbull Same packets arriving more than oncebull Some packets are lostdiscardedbull Traffic congestion control

942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

Link

Application

Transport

Internet

Link

Physical Network

bull Eg TCP (connection-oriented) UDPbull End-to-end message transfer between

hosts applicationsbull Each application on a host is associated

with a port numberbull IP address + port number will identify an

application end-point

15

Applications Email

bull Your email client program downloads incoming emails from mail server (imapgmailcom popgmailcom)

bull Outgoing emails are sent to mail server (smtpgmailcom)bull Mail servers handle the routing of emails using SMTP protocol which

operates on port 25 or 587ndash Lookup IP address of destination hostname in the email address using DNSndash Relaying email as packets to that IP address

942012 Lipyeow Lim -- University of Hawaii at Manoa

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

Network

Mail Server Mail Server

Network Internet

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

Mail Client Mail Client

16

Sample Email HeaderDelivered-To strevguhrelayhawaiieduReceived by 10581456 with SMTP id sq6csp687725veb

Mon 3 Sep 2012203901 -0700 (PDT)Received by 106812938 with SMTP id

nt6mr43102232pbb761346729940698 Mon03 Sep 2012 203900 -0700 (PDT)Return-Path ltpostmasterlaulimahawaiiedugtReceived from mta11itshawaiiedu (mta11itshawaiiedu

[128171224147])by mxgooglecom with ESMTPS id

px6si25354378pbc21420120903203853(version=TLSv1SSLv3 cipher=RC4-MD5) Mon 03 Sep 2012

203900 -0700 (PDT)Received-SPF pass (googlecom domain of

postmasterlaulimahawaiiedudesignates 12817122458 as permitted sender) client-ip=

12817122458Authentication-Results mxgooglecom spf=pass (googlecom

domain ofpostmasterlaulimahawaiiedu designates 12817122458

as permitted sender)smtpmail=postmasterlaulimahawaiieduMIME-version 10Content-type multipartmixed

boundary=Boundary_(ID_3RY8N2VbJHb4tH5siR1eww)

Received from pmx11itshawaiiedu (pmx11itshawaiiedu [12817122458]) by

mta11itshawaiiedu (Sun Java(tm) System Messaging Server 63-1101 (built

Feb 12 2010 32bit)) with ESMTP id lt0M9T0071I3GJ4F40mta11itshawaiiedugt

Mon 03 Sep 2012 173845 -1000 (HST)Received from kuhiitshawaiiedu (kuhiitshawaiiedu

[12817125223]) bypmx11itshawaiiedu (Postfix) with ESMTP id E587118C023

Mon 03 Sep 2012173842 -1000 (HST)Received from sak24itshawaiiedu (sak24itshawaiiedu

[128171225199])by kuhiitshawaiiedu (812108126) with ESMTP id

q843ccvH023430 Mon 03Sep 2012 173838 -1000 (HST)Date Mon 03 Sep 2012 173833 -1000 (HST)From Dennis Streveler ltstrevhawaiiedugtCc strevhawaiiedu ltstrevhawaiiedugtMessage-id lt

11298755423101346729913602JavaMailsakaisak24itshawaiiedugt

Subject ICS 101 Help Tuesday lecture -- Everything you THOUGHT you knew

about NETWORKS and then someX-Mailer sakai-mailsender

942012 Lipyeow Lim -- University of Hawaii at Manoa

8

TCPIP Four Layer Model

942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

Link

bull Process to process communicates data to other processesapplications on the same host or on other hosts

bull Eg SMTP FTP SSH HTTP

bull Host to host communicates data to other host on the same network on on other networks

bull Hides the topology of the networkbull Flow control error correction connection controlbull Eg TCP UDP

bull Inter-network communicates data to other networksbull Deals with addressing and routing of datagrams to next

networkbull Eg IPv4 IPv6

bull Transmit data to other network interfaces on the local networkbull Eg Ethernet WiFi 80211

9

Link Layer

Data packet arrives from upper layer (Internet layer)bull If packet is too big break packet into smaller fragments (`framesrsquo)bull Embed data packet in a link layer packet with link layer header sequence

number error correction code etcbull Link layer packets gets transmitted on physical linkbull Link layer protocol governs how transmission over physical link is done Eg

Carrier sense multiple accessBottom-up process is similar on the receiving host

942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

Link

Application

Transport

Internet

Link

Physical Network

bull Eg Ethernet WiFi 80211bull A host can have multiple network interface

cards (eg Laptops typically have an ethernet interface and a WiFi interface)

bull Each interface has a 48-bit physical address that is hardwired to the hardware

10

Internet Layer

Data packet arrives from Transport layerbull Embed data packet in an IPv4 packet with IP header etcbull Pass packet to Link layer

Data packet arrives from Link layerbull Check IP header if packet destination is for this host If yes strip header and

pass to Transport layerbull Otherwise forward packet (routing)942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

Link

Application

Transport

Internet

Link

Physical Network

bull Eg IPv4bull Connects multiple networks togetherbull Each network interface of a host is

associated with an 32-bit IPv4 addressbull IP address is not hardwired but assigned in

the software

11

IPv4 Addresses amp Domain Name Service

bull IP addresses are 32 bit numbers often written in 4 octets 1281711013

bull Each address is also split into two partsndash Prefix is the network addressndash Suffix is the host address within that network

bull Domain Name Servers provide a service that translates more meaningful names to IP addressesndash Uhunixhawaiiedu = 12817124197ndash www2hawaiiedu = 128171224150

942012 Lipyeow Lim -- University of Hawaii at Manoa

128 171 10 13

Network Address Host Address

0 3116

12

IPv4 amp Inter-network Routing

For routersbull Examine destination IP addressbull Look up routing tables to determine outgoing networkbull Pass packet to link layer of that outgoing networkbull Best effort delivery ndash no guarantees

942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

LinkInternet

Link

Ethernet Network

Internet

Link

Application

Transport

Internet

Link

Ethernet NetworkFibre Network

host host

RouterRouter

13

Packet Routing Exercise

942012 Lipyeow Lim -- University of Hawaii at Manoa

14

Transport Layer

TCP provides a reliable communication channel between two host applications by addressing several issues

bull Data packets arriving out of orderbull Data packets are corruptedbull Same packets arriving more than oncebull Some packets are lostdiscardedbull Traffic congestion control

942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

Link

Application

Transport

Internet

Link

Physical Network

bull Eg TCP (connection-oriented) UDPbull End-to-end message transfer between

hosts applicationsbull Each application on a host is associated

with a port numberbull IP address + port number will identify an

application end-point

15

Applications Email

bull Your email client program downloads incoming emails from mail server (imapgmailcom popgmailcom)

bull Outgoing emails are sent to mail server (smtpgmailcom)bull Mail servers handle the routing of emails using SMTP protocol which

operates on port 25 or 587ndash Lookup IP address of destination hostname in the email address using DNSndash Relaying email as packets to that IP address

942012 Lipyeow Lim -- University of Hawaii at Manoa

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

Network

Mail Server Mail Server

Network Internet

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

Mail Client Mail Client

16

Sample Email HeaderDelivered-To strevguhrelayhawaiieduReceived by 10581456 with SMTP id sq6csp687725veb

Mon 3 Sep 2012203901 -0700 (PDT)Received by 106812938 with SMTP id

nt6mr43102232pbb761346729940698 Mon03 Sep 2012 203900 -0700 (PDT)Return-Path ltpostmasterlaulimahawaiiedugtReceived from mta11itshawaiiedu (mta11itshawaiiedu

[128171224147])by mxgooglecom with ESMTPS id

px6si25354378pbc21420120903203853(version=TLSv1SSLv3 cipher=RC4-MD5) Mon 03 Sep 2012

203900 -0700 (PDT)Received-SPF pass (googlecom domain of

postmasterlaulimahawaiiedudesignates 12817122458 as permitted sender) client-ip=

12817122458Authentication-Results mxgooglecom spf=pass (googlecom

domain ofpostmasterlaulimahawaiiedu designates 12817122458

as permitted sender)smtpmail=postmasterlaulimahawaiieduMIME-version 10Content-type multipartmixed

boundary=Boundary_(ID_3RY8N2VbJHb4tH5siR1eww)

Received from pmx11itshawaiiedu (pmx11itshawaiiedu [12817122458]) by

mta11itshawaiiedu (Sun Java(tm) System Messaging Server 63-1101 (built

Feb 12 2010 32bit)) with ESMTP id lt0M9T0071I3GJ4F40mta11itshawaiiedugt

Mon 03 Sep 2012 173845 -1000 (HST)Received from kuhiitshawaiiedu (kuhiitshawaiiedu

[12817125223]) bypmx11itshawaiiedu (Postfix) with ESMTP id E587118C023

Mon 03 Sep 2012173842 -1000 (HST)Received from sak24itshawaiiedu (sak24itshawaiiedu

[128171225199])by kuhiitshawaiiedu (812108126) with ESMTP id

q843ccvH023430 Mon 03Sep 2012 173838 -1000 (HST)Date Mon 03 Sep 2012 173833 -1000 (HST)From Dennis Streveler ltstrevhawaiiedugtCc strevhawaiiedu ltstrevhawaiiedugtMessage-id lt

11298755423101346729913602JavaMailsakaisak24itshawaiiedugt

Subject ICS 101 Help Tuesday lecture -- Everything you THOUGHT you knew

about NETWORKS and then someX-Mailer sakai-mailsender

942012 Lipyeow Lim -- University of Hawaii at Manoa

9

Link Layer

Data packet arrives from upper layer (Internet layer)bull If packet is too big break packet into smaller fragments (`framesrsquo)bull Embed data packet in a link layer packet with link layer header sequence

number error correction code etcbull Link layer packets gets transmitted on physical linkbull Link layer protocol governs how transmission over physical link is done Eg

Carrier sense multiple accessBottom-up process is similar on the receiving host

942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

Link

Application

Transport

Internet

Link

Physical Network

bull Eg Ethernet WiFi 80211bull A host can have multiple network interface

cards (eg Laptops typically have an ethernet interface and a WiFi interface)

bull Each interface has a 48-bit physical address that is hardwired to the hardware

10

Internet Layer

Data packet arrives from Transport layerbull Embed data packet in an IPv4 packet with IP header etcbull Pass packet to Link layer

Data packet arrives from Link layerbull Check IP header if packet destination is for this host If yes strip header and

pass to Transport layerbull Otherwise forward packet (routing)942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

Link

Application

Transport

Internet

Link

Physical Network

bull Eg IPv4bull Connects multiple networks togetherbull Each network interface of a host is

associated with an 32-bit IPv4 addressbull IP address is not hardwired but assigned in

the software

11

IPv4 Addresses amp Domain Name Service

bull IP addresses are 32 bit numbers often written in 4 octets 1281711013

bull Each address is also split into two partsndash Prefix is the network addressndash Suffix is the host address within that network

bull Domain Name Servers provide a service that translates more meaningful names to IP addressesndash Uhunixhawaiiedu = 12817124197ndash www2hawaiiedu = 128171224150

942012 Lipyeow Lim -- University of Hawaii at Manoa

128 171 10 13

Network Address Host Address

0 3116

12

IPv4 amp Inter-network Routing

For routersbull Examine destination IP addressbull Look up routing tables to determine outgoing networkbull Pass packet to link layer of that outgoing networkbull Best effort delivery ndash no guarantees

942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

LinkInternet

Link

Ethernet Network

Internet

Link

Application

Transport

Internet

Link

Ethernet NetworkFibre Network

host host

RouterRouter

13

Packet Routing Exercise

942012 Lipyeow Lim -- University of Hawaii at Manoa

14

Transport Layer

TCP provides a reliable communication channel between two host applications by addressing several issues

bull Data packets arriving out of orderbull Data packets are corruptedbull Same packets arriving more than oncebull Some packets are lostdiscardedbull Traffic congestion control

942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

Link

Application

Transport

Internet

Link

Physical Network

bull Eg TCP (connection-oriented) UDPbull End-to-end message transfer between

hosts applicationsbull Each application on a host is associated

with a port numberbull IP address + port number will identify an

application end-point

15

Applications Email

bull Your email client program downloads incoming emails from mail server (imapgmailcom popgmailcom)

bull Outgoing emails are sent to mail server (smtpgmailcom)bull Mail servers handle the routing of emails using SMTP protocol which

operates on port 25 or 587ndash Lookup IP address of destination hostname in the email address using DNSndash Relaying email as packets to that IP address

942012 Lipyeow Lim -- University of Hawaii at Manoa

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

Network

Mail Server Mail Server

Network Internet

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

Mail Client Mail Client

16

Sample Email HeaderDelivered-To strevguhrelayhawaiieduReceived by 10581456 with SMTP id sq6csp687725veb

Mon 3 Sep 2012203901 -0700 (PDT)Received by 106812938 with SMTP id

nt6mr43102232pbb761346729940698 Mon03 Sep 2012 203900 -0700 (PDT)Return-Path ltpostmasterlaulimahawaiiedugtReceived from mta11itshawaiiedu (mta11itshawaiiedu

[128171224147])by mxgooglecom with ESMTPS id

px6si25354378pbc21420120903203853(version=TLSv1SSLv3 cipher=RC4-MD5) Mon 03 Sep 2012

203900 -0700 (PDT)Received-SPF pass (googlecom domain of

postmasterlaulimahawaiiedudesignates 12817122458 as permitted sender) client-ip=

12817122458Authentication-Results mxgooglecom spf=pass (googlecom

domain ofpostmasterlaulimahawaiiedu designates 12817122458

as permitted sender)smtpmail=postmasterlaulimahawaiieduMIME-version 10Content-type multipartmixed

boundary=Boundary_(ID_3RY8N2VbJHb4tH5siR1eww)

Received from pmx11itshawaiiedu (pmx11itshawaiiedu [12817122458]) by

mta11itshawaiiedu (Sun Java(tm) System Messaging Server 63-1101 (built

Feb 12 2010 32bit)) with ESMTP id lt0M9T0071I3GJ4F40mta11itshawaiiedugt

Mon 03 Sep 2012 173845 -1000 (HST)Received from kuhiitshawaiiedu (kuhiitshawaiiedu

[12817125223]) bypmx11itshawaiiedu (Postfix) with ESMTP id E587118C023

Mon 03 Sep 2012173842 -1000 (HST)Received from sak24itshawaiiedu (sak24itshawaiiedu

[128171225199])by kuhiitshawaiiedu (812108126) with ESMTP id

q843ccvH023430 Mon 03Sep 2012 173838 -1000 (HST)Date Mon 03 Sep 2012 173833 -1000 (HST)From Dennis Streveler ltstrevhawaiiedugtCc strevhawaiiedu ltstrevhawaiiedugtMessage-id lt

11298755423101346729913602JavaMailsakaisak24itshawaiiedugt

Subject ICS 101 Help Tuesday lecture -- Everything you THOUGHT you knew

about NETWORKS and then someX-Mailer sakai-mailsender

942012 Lipyeow Lim -- University of Hawaii at Manoa

10

Internet Layer

Data packet arrives from Transport layerbull Embed data packet in an IPv4 packet with IP header etcbull Pass packet to Link layer

Data packet arrives from Link layerbull Check IP header if packet destination is for this host If yes strip header and

pass to Transport layerbull Otherwise forward packet (routing)942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

Link

Application

Transport

Internet

Link

Physical Network

bull Eg IPv4bull Connects multiple networks togetherbull Each network interface of a host is

associated with an 32-bit IPv4 addressbull IP address is not hardwired but assigned in

the software

11

IPv4 Addresses amp Domain Name Service

bull IP addresses are 32 bit numbers often written in 4 octets 1281711013

bull Each address is also split into two partsndash Prefix is the network addressndash Suffix is the host address within that network

bull Domain Name Servers provide a service that translates more meaningful names to IP addressesndash Uhunixhawaiiedu = 12817124197ndash www2hawaiiedu = 128171224150

942012 Lipyeow Lim -- University of Hawaii at Manoa

128 171 10 13

Network Address Host Address

0 3116

12

IPv4 amp Inter-network Routing

For routersbull Examine destination IP addressbull Look up routing tables to determine outgoing networkbull Pass packet to link layer of that outgoing networkbull Best effort delivery ndash no guarantees

942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

LinkInternet

Link

Ethernet Network

Internet

Link

Application

Transport

Internet

Link

Ethernet NetworkFibre Network

host host

RouterRouter

13

Packet Routing Exercise

942012 Lipyeow Lim -- University of Hawaii at Manoa

14

Transport Layer

TCP provides a reliable communication channel between two host applications by addressing several issues

bull Data packets arriving out of orderbull Data packets are corruptedbull Same packets arriving more than oncebull Some packets are lostdiscardedbull Traffic congestion control

942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

Link

Application

Transport

Internet

Link

Physical Network

bull Eg TCP (connection-oriented) UDPbull End-to-end message transfer between

hosts applicationsbull Each application on a host is associated

with a port numberbull IP address + port number will identify an

application end-point

15

Applications Email

bull Your email client program downloads incoming emails from mail server (imapgmailcom popgmailcom)

bull Outgoing emails are sent to mail server (smtpgmailcom)bull Mail servers handle the routing of emails using SMTP protocol which

operates on port 25 or 587ndash Lookup IP address of destination hostname in the email address using DNSndash Relaying email as packets to that IP address

942012 Lipyeow Lim -- University of Hawaii at Manoa

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

Network

Mail Server Mail Server

Network Internet

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

Mail Client Mail Client

16

Sample Email HeaderDelivered-To strevguhrelayhawaiieduReceived by 10581456 with SMTP id sq6csp687725veb

Mon 3 Sep 2012203901 -0700 (PDT)Received by 106812938 with SMTP id

nt6mr43102232pbb761346729940698 Mon03 Sep 2012 203900 -0700 (PDT)Return-Path ltpostmasterlaulimahawaiiedugtReceived from mta11itshawaiiedu (mta11itshawaiiedu

[128171224147])by mxgooglecom with ESMTPS id

px6si25354378pbc21420120903203853(version=TLSv1SSLv3 cipher=RC4-MD5) Mon 03 Sep 2012

203900 -0700 (PDT)Received-SPF pass (googlecom domain of

postmasterlaulimahawaiiedudesignates 12817122458 as permitted sender) client-ip=

12817122458Authentication-Results mxgooglecom spf=pass (googlecom

domain ofpostmasterlaulimahawaiiedu designates 12817122458

as permitted sender)smtpmail=postmasterlaulimahawaiieduMIME-version 10Content-type multipartmixed

boundary=Boundary_(ID_3RY8N2VbJHb4tH5siR1eww)

Received from pmx11itshawaiiedu (pmx11itshawaiiedu [12817122458]) by

mta11itshawaiiedu (Sun Java(tm) System Messaging Server 63-1101 (built

Feb 12 2010 32bit)) with ESMTP id lt0M9T0071I3GJ4F40mta11itshawaiiedugt

Mon 03 Sep 2012 173845 -1000 (HST)Received from kuhiitshawaiiedu (kuhiitshawaiiedu

[12817125223]) bypmx11itshawaiiedu (Postfix) with ESMTP id E587118C023

Mon 03 Sep 2012173842 -1000 (HST)Received from sak24itshawaiiedu (sak24itshawaiiedu

[128171225199])by kuhiitshawaiiedu (812108126) with ESMTP id

q843ccvH023430 Mon 03Sep 2012 173838 -1000 (HST)Date Mon 03 Sep 2012 173833 -1000 (HST)From Dennis Streveler ltstrevhawaiiedugtCc strevhawaiiedu ltstrevhawaiiedugtMessage-id lt

11298755423101346729913602JavaMailsakaisak24itshawaiiedugt

Subject ICS 101 Help Tuesday lecture -- Everything you THOUGHT you knew

about NETWORKS and then someX-Mailer sakai-mailsender

942012 Lipyeow Lim -- University of Hawaii at Manoa

11

IPv4 Addresses amp Domain Name Service

bull IP addresses are 32 bit numbers often written in 4 octets 1281711013

bull Each address is also split into two partsndash Prefix is the network addressndash Suffix is the host address within that network

bull Domain Name Servers provide a service that translates more meaningful names to IP addressesndash Uhunixhawaiiedu = 12817124197ndash www2hawaiiedu = 128171224150

942012 Lipyeow Lim -- University of Hawaii at Manoa

128 171 10 13

Network Address Host Address

0 3116

12

IPv4 amp Inter-network Routing

For routersbull Examine destination IP addressbull Look up routing tables to determine outgoing networkbull Pass packet to link layer of that outgoing networkbull Best effort delivery ndash no guarantees

942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

LinkInternet

Link

Ethernet Network

Internet

Link

Application

Transport

Internet

Link

Ethernet NetworkFibre Network

host host

RouterRouter

13

Packet Routing Exercise

942012 Lipyeow Lim -- University of Hawaii at Manoa

14

Transport Layer

TCP provides a reliable communication channel between two host applications by addressing several issues

bull Data packets arriving out of orderbull Data packets are corruptedbull Same packets arriving more than oncebull Some packets are lostdiscardedbull Traffic congestion control

942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

Link

Application

Transport

Internet

Link

Physical Network

bull Eg TCP (connection-oriented) UDPbull End-to-end message transfer between

hosts applicationsbull Each application on a host is associated

with a port numberbull IP address + port number will identify an

application end-point

15

Applications Email

bull Your email client program downloads incoming emails from mail server (imapgmailcom popgmailcom)

bull Outgoing emails are sent to mail server (smtpgmailcom)bull Mail servers handle the routing of emails using SMTP protocol which

operates on port 25 or 587ndash Lookup IP address of destination hostname in the email address using DNSndash Relaying email as packets to that IP address

942012 Lipyeow Lim -- University of Hawaii at Manoa

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

Network

Mail Server Mail Server

Network Internet

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

Mail Client Mail Client

16

Sample Email HeaderDelivered-To strevguhrelayhawaiieduReceived by 10581456 with SMTP id sq6csp687725veb

Mon 3 Sep 2012203901 -0700 (PDT)Received by 106812938 with SMTP id

nt6mr43102232pbb761346729940698 Mon03 Sep 2012 203900 -0700 (PDT)Return-Path ltpostmasterlaulimahawaiiedugtReceived from mta11itshawaiiedu (mta11itshawaiiedu

[128171224147])by mxgooglecom with ESMTPS id

px6si25354378pbc21420120903203853(version=TLSv1SSLv3 cipher=RC4-MD5) Mon 03 Sep 2012

203900 -0700 (PDT)Received-SPF pass (googlecom domain of

postmasterlaulimahawaiiedudesignates 12817122458 as permitted sender) client-ip=

12817122458Authentication-Results mxgooglecom spf=pass (googlecom

domain ofpostmasterlaulimahawaiiedu designates 12817122458

as permitted sender)smtpmail=postmasterlaulimahawaiieduMIME-version 10Content-type multipartmixed

boundary=Boundary_(ID_3RY8N2VbJHb4tH5siR1eww)

Received from pmx11itshawaiiedu (pmx11itshawaiiedu [12817122458]) by

mta11itshawaiiedu (Sun Java(tm) System Messaging Server 63-1101 (built

Feb 12 2010 32bit)) with ESMTP id lt0M9T0071I3GJ4F40mta11itshawaiiedugt

Mon 03 Sep 2012 173845 -1000 (HST)Received from kuhiitshawaiiedu (kuhiitshawaiiedu

[12817125223]) bypmx11itshawaiiedu (Postfix) with ESMTP id E587118C023

Mon 03 Sep 2012173842 -1000 (HST)Received from sak24itshawaiiedu (sak24itshawaiiedu

[128171225199])by kuhiitshawaiiedu (812108126) with ESMTP id

q843ccvH023430 Mon 03Sep 2012 173838 -1000 (HST)Date Mon 03 Sep 2012 173833 -1000 (HST)From Dennis Streveler ltstrevhawaiiedugtCc strevhawaiiedu ltstrevhawaiiedugtMessage-id lt

11298755423101346729913602JavaMailsakaisak24itshawaiiedugt

Subject ICS 101 Help Tuesday lecture -- Everything you THOUGHT you knew

about NETWORKS and then someX-Mailer sakai-mailsender

942012 Lipyeow Lim -- University of Hawaii at Manoa

12

IPv4 amp Inter-network Routing

For routersbull Examine destination IP addressbull Look up routing tables to determine outgoing networkbull Pass packet to link layer of that outgoing networkbull Best effort delivery ndash no guarantees

942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

LinkInternet

Link

Ethernet Network

Internet

Link

Application

Transport

Internet

Link

Ethernet NetworkFibre Network

host host

RouterRouter

13

Packet Routing Exercise

942012 Lipyeow Lim -- University of Hawaii at Manoa

14

Transport Layer

TCP provides a reliable communication channel between two host applications by addressing several issues

bull Data packets arriving out of orderbull Data packets are corruptedbull Same packets arriving more than oncebull Some packets are lostdiscardedbull Traffic congestion control

942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

Link

Application

Transport

Internet

Link

Physical Network

bull Eg TCP (connection-oriented) UDPbull End-to-end message transfer between

hosts applicationsbull Each application on a host is associated

with a port numberbull IP address + port number will identify an

application end-point

15

Applications Email

bull Your email client program downloads incoming emails from mail server (imapgmailcom popgmailcom)

bull Outgoing emails are sent to mail server (smtpgmailcom)bull Mail servers handle the routing of emails using SMTP protocol which

operates on port 25 or 587ndash Lookup IP address of destination hostname in the email address using DNSndash Relaying email as packets to that IP address

942012 Lipyeow Lim -- University of Hawaii at Manoa

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

Network

Mail Server Mail Server

Network Internet

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

Mail Client Mail Client

16

Sample Email HeaderDelivered-To strevguhrelayhawaiieduReceived by 10581456 with SMTP id sq6csp687725veb

Mon 3 Sep 2012203901 -0700 (PDT)Received by 106812938 with SMTP id

nt6mr43102232pbb761346729940698 Mon03 Sep 2012 203900 -0700 (PDT)Return-Path ltpostmasterlaulimahawaiiedugtReceived from mta11itshawaiiedu (mta11itshawaiiedu

[128171224147])by mxgooglecom with ESMTPS id

px6si25354378pbc21420120903203853(version=TLSv1SSLv3 cipher=RC4-MD5) Mon 03 Sep 2012

203900 -0700 (PDT)Received-SPF pass (googlecom domain of

postmasterlaulimahawaiiedudesignates 12817122458 as permitted sender) client-ip=

12817122458Authentication-Results mxgooglecom spf=pass (googlecom

domain ofpostmasterlaulimahawaiiedu designates 12817122458

as permitted sender)smtpmail=postmasterlaulimahawaiieduMIME-version 10Content-type multipartmixed

boundary=Boundary_(ID_3RY8N2VbJHb4tH5siR1eww)

Received from pmx11itshawaiiedu (pmx11itshawaiiedu [12817122458]) by

mta11itshawaiiedu (Sun Java(tm) System Messaging Server 63-1101 (built

Feb 12 2010 32bit)) with ESMTP id lt0M9T0071I3GJ4F40mta11itshawaiiedugt

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q843ccvH023430 Mon 03Sep 2012 173838 -1000 (HST)Date Mon 03 Sep 2012 173833 -1000 (HST)From Dennis Streveler ltstrevhawaiiedugtCc strevhawaiiedu ltstrevhawaiiedugtMessage-id lt

11298755423101346729913602JavaMailsakaisak24itshawaiiedugt

Subject ICS 101 Help Tuesday lecture -- Everything you THOUGHT you knew

about NETWORKS and then someX-Mailer sakai-mailsender

942012 Lipyeow Lim -- University of Hawaii at Manoa

13

Packet Routing Exercise

942012 Lipyeow Lim -- University of Hawaii at Manoa

14

Transport Layer

TCP provides a reliable communication channel between two host applications by addressing several issues

bull Data packets arriving out of orderbull Data packets are corruptedbull Same packets arriving more than oncebull Some packets are lostdiscardedbull Traffic congestion control

942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

Link

Application

Transport

Internet

Link

Physical Network

bull Eg TCP (connection-oriented) UDPbull End-to-end message transfer between

hosts applicationsbull Each application on a host is associated

with a port numberbull IP address + port number will identify an

application end-point

15

Applications Email

bull Your email client program downloads incoming emails from mail server (imapgmailcom popgmailcom)

bull Outgoing emails are sent to mail server (smtpgmailcom)bull Mail servers handle the routing of emails using SMTP protocol which

operates on port 25 or 587ndash Lookup IP address of destination hostname in the email address using DNSndash Relaying email as packets to that IP address

942012 Lipyeow Lim -- University of Hawaii at Manoa

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

Network

Mail Server Mail Server

Network Internet

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

Mail Client Mail Client

16

Sample Email HeaderDelivered-To strevguhrelayhawaiieduReceived by 10581456 with SMTP id sq6csp687725veb

Mon 3 Sep 2012203901 -0700 (PDT)Received by 106812938 with SMTP id

nt6mr43102232pbb761346729940698 Mon03 Sep 2012 203900 -0700 (PDT)Return-Path ltpostmasterlaulimahawaiiedugtReceived from mta11itshawaiiedu (mta11itshawaiiedu

[128171224147])by mxgooglecom with ESMTPS id

px6si25354378pbc21420120903203853(version=TLSv1SSLv3 cipher=RC4-MD5) Mon 03 Sep 2012

203900 -0700 (PDT)Received-SPF pass (googlecom domain of

postmasterlaulimahawaiiedudesignates 12817122458 as permitted sender) client-ip=

12817122458Authentication-Results mxgooglecom spf=pass (googlecom

domain ofpostmasterlaulimahawaiiedu designates 12817122458

as permitted sender)smtpmail=postmasterlaulimahawaiieduMIME-version 10Content-type multipartmixed

boundary=Boundary_(ID_3RY8N2VbJHb4tH5siR1eww)

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mta11itshawaiiedu (Sun Java(tm) System Messaging Server 63-1101 (built

Feb 12 2010 32bit)) with ESMTP id lt0M9T0071I3GJ4F40mta11itshawaiiedugt

Mon 03 Sep 2012 173845 -1000 (HST)Received from kuhiitshawaiiedu (kuhiitshawaiiedu

[12817125223]) bypmx11itshawaiiedu (Postfix) with ESMTP id E587118C023

Mon 03 Sep 2012173842 -1000 (HST)Received from sak24itshawaiiedu (sak24itshawaiiedu

[128171225199])by kuhiitshawaiiedu (812108126) with ESMTP id

q843ccvH023430 Mon 03Sep 2012 173838 -1000 (HST)Date Mon 03 Sep 2012 173833 -1000 (HST)From Dennis Streveler ltstrevhawaiiedugtCc strevhawaiiedu ltstrevhawaiiedugtMessage-id lt

11298755423101346729913602JavaMailsakaisak24itshawaiiedugt

Subject ICS 101 Help Tuesday lecture -- Everything you THOUGHT you knew

about NETWORKS and then someX-Mailer sakai-mailsender

942012 Lipyeow Lim -- University of Hawaii at Manoa

14

Transport Layer

TCP provides a reliable communication channel between two host applications by addressing several issues

bull Data packets arriving out of orderbull Data packets are corruptedbull Same packets arriving more than oncebull Some packets are lostdiscardedbull Traffic congestion control

942012 Lipyeow Lim -- University of Hawaii at Manoa

Application

Transport

Internet

Link

Application

Transport

Internet

Link

Physical Network

bull Eg TCP (connection-oriented) UDPbull End-to-end message transfer between

hosts applicationsbull Each application on a host is associated

with a port numberbull IP address + port number will identify an

application end-point

15

Applications Email

bull Your email client program downloads incoming emails from mail server (imapgmailcom popgmailcom)

bull Outgoing emails are sent to mail server (smtpgmailcom)bull Mail servers handle the routing of emails using SMTP protocol which

operates on port 25 or 587ndash Lookup IP address of destination hostname in the email address using DNSndash Relaying email as packets to that IP address

942012 Lipyeow Lim -- University of Hawaii at Manoa

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

Network

Mail Server Mail Server

Network Internet

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

Mail Client Mail Client

16

Sample Email HeaderDelivered-To strevguhrelayhawaiieduReceived by 10581456 with SMTP id sq6csp687725veb

Mon 3 Sep 2012203901 -0700 (PDT)Received by 106812938 with SMTP id

nt6mr43102232pbb761346729940698 Mon03 Sep 2012 203900 -0700 (PDT)Return-Path ltpostmasterlaulimahawaiiedugtReceived from mta11itshawaiiedu (mta11itshawaiiedu

[128171224147])by mxgooglecom with ESMTPS id

px6si25354378pbc21420120903203853(version=TLSv1SSLv3 cipher=RC4-MD5) Mon 03 Sep 2012

203900 -0700 (PDT)Received-SPF pass (googlecom domain of

postmasterlaulimahawaiiedudesignates 12817122458 as permitted sender) client-ip=

12817122458Authentication-Results mxgooglecom spf=pass (googlecom

domain ofpostmasterlaulimahawaiiedu designates 12817122458

as permitted sender)smtpmail=postmasterlaulimahawaiieduMIME-version 10Content-type multipartmixed

boundary=Boundary_(ID_3RY8N2VbJHb4tH5siR1eww)

Received from pmx11itshawaiiedu (pmx11itshawaiiedu [12817122458]) by

mta11itshawaiiedu (Sun Java(tm) System Messaging Server 63-1101 (built

Feb 12 2010 32bit)) with ESMTP id lt0M9T0071I3GJ4F40mta11itshawaiiedugt

Mon 03 Sep 2012 173845 -1000 (HST)Received from kuhiitshawaiiedu (kuhiitshawaiiedu

[12817125223]) bypmx11itshawaiiedu (Postfix) with ESMTP id E587118C023

Mon 03 Sep 2012173842 -1000 (HST)Received from sak24itshawaiiedu (sak24itshawaiiedu

[128171225199])by kuhiitshawaiiedu (812108126) with ESMTP id

q843ccvH023430 Mon 03Sep 2012 173838 -1000 (HST)Date Mon 03 Sep 2012 173833 -1000 (HST)From Dennis Streveler ltstrevhawaiiedugtCc strevhawaiiedu ltstrevhawaiiedugtMessage-id lt

11298755423101346729913602JavaMailsakaisak24itshawaiiedugt

Subject ICS 101 Help Tuesday lecture -- Everything you THOUGHT you knew

about NETWORKS and then someX-Mailer sakai-mailsender

942012 Lipyeow Lim -- University of Hawaii at Manoa

15

Applications Email

bull Your email client program downloads incoming emails from mail server (imapgmailcom popgmailcom)

bull Outgoing emails are sent to mail server (smtpgmailcom)bull Mail servers handle the routing of emails using SMTP protocol which

operates on port 25 or 587ndash Lookup IP address of destination hostname in the email address using DNSndash Relaying email as packets to that IP address

942012 Lipyeow Lim -- University of Hawaii at Manoa

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

Network

Mail Server Mail Server

Network Internet

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

POPIMAPSMTP

Transport TCP

Internet IPv4

Link

Mail Client Mail Client

16

Sample Email HeaderDelivered-To strevguhrelayhawaiieduReceived by 10581456 with SMTP id sq6csp687725veb

Mon 3 Sep 2012203901 -0700 (PDT)Received by 106812938 with SMTP id

nt6mr43102232pbb761346729940698 Mon03 Sep 2012 203900 -0700 (PDT)Return-Path ltpostmasterlaulimahawaiiedugtReceived from mta11itshawaiiedu (mta11itshawaiiedu

[128171224147])by mxgooglecom with ESMTPS id

px6si25354378pbc21420120903203853(version=TLSv1SSLv3 cipher=RC4-MD5) Mon 03 Sep 2012

203900 -0700 (PDT)Received-SPF pass (googlecom domain of

postmasterlaulimahawaiiedudesignates 12817122458 as permitted sender) client-ip=

12817122458Authentication-Results mxgooglecom spf=pass (googlecom

domain ofpostmasterlaulimahawaiiedu designates 12817122458

as permitted sender)smtpmail=postmasterlaulimahawaiieduMIME-version 10Content-type multipartmixed

boundary=Boundary_(ID_3RY8N2VbJHb4tH5siR1eww)

Received from pmx11itshawaiiedu (pmx11itshawaiiedu [12817122458]) by

mta11itshawaiiedu (Sun Java(tm) System Messaging Server 63-1101 (built

Feb 12 2010 32bit)) with ESMTP id lt0M9T0071I3GJ4F40mta11itshawaiiedugt

Mon 03 Sep 2012 173845 -1000 (HST)Received from kuhiitshawaiiedu (kuhiitshawaiiedu

[12817125223]) bypmx11itshawaiiedu (Postfix) with ESMTP id E587118C023

Mon 03 Sep 2012173842 -1000 (HST)Received from sak24itshawaiiedu (sak24itshawaiiedu

[128171225199])by kuhiitshawaiiedu (812108126) with ESMTP id

q843ccvH023430 Mon 03Sep 2012 173838 -1000 (HST)Date Mon 03 Sep 2012 173833 -1000 (HST)From Dennis Streveler ltstrevhawaiiedugtCc strevhawaiiedu ltstrevhawaiiedugtMessage-id lt

11298755423101346729913602JavaMailsakaisak24itshawaiiedugt

Subject ICS 101 Help Tuesday lecture -- Everything you THOUGHT you knew

about NETWORKS and then someX-Mailer sakai-mailsender

942012 Lipyeow Lim -- University of Hawaii at Manoa

16

Sample Email HeaderDelivered-To strevguhrelayhawaiieduReceived by 10581456 with SMTP id sq6csp687725veb

Mon 3 Sep 2012203901 -0700 (PDT)Received by 106812938 with SMTP id

nt6mr43102232pbb761346729940698 Mon03 Sep 2012 203900 -0700 (PDT)Return-Path ltpostmasterlaulimahawaiiedugtReceived from mta11itshawaiiedu (mta11itshawaiiedu

[128171224147])by mxgooglecom with ESMTPS id

px6si25354378pbc21420120903203853(version=TLSv1SSLv3 cipher=RC4-MD5) Mon 03 Sep 2012

203900 -0700 (PDT)Received-SPF pass (googlecom domain of

postmasterlaulimahawaiiedudesignates 12817122458 as permitted sender) client-ip=

12817122458Authentication-Results mxgooglecom spf=pass (googlecom

domain ofpostmasterlaulimahawaiiedu designates 12817122458

as permitted sender)smtpmail=postmasterlaulimahawaiieduMIME-version 10Content-type multipartmixed

boundary=Boundary_(ID_3RY8N2VbJHb4tH5siR1eww)

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Feb 12 2010 32bit)) with ESMTP id lt0M9T0071I3GJ4F40mta11itshawaiiedugt

Mon 03 Sep 2012 173845 -1000 (HST)Received from kuhiitshawaiiedu (kuhiitshawaiiedu

[12817125223]) bypmx11itshawaiiedu (Postfix) with ESMTP id E587118C023

Mon 03 Sep 2012173842 -1000 (HST)Received from sak24itshawaiiedu (sak24itshawaiiedu

[128171225199])by kuhiitshawaiiedu (812108126) with ESMTP id

q843ccvH023430 Mon 03Sep 2012 173838 -1000 (HST)Date Mon 03 Sep 2012 173833 -1000 (HST)From Dennis Streveler ltstrevhawaiiedugtCc strevhawaiiedu ltstrevhawaiiedugtMessage-id lt

11298755423101346729913602JavaMailsakaisak24itshawaiiedugt

Subject ICS 101 Help Tuesday lecture -- Everything you THOUGHT you knew

about NETWORKS and then someX-Mailer sakai-mailsender

942012 Lipyeow Lim -- University of Hawaii at Manoa

17

Applications HTTP

942012 Lipyeow Lim -- University of Hawaii at Manoa

HTTP

Transport TCP

Internet IPv4

Link

HTTP Server

Internet

HTTP

Transport TCP

Internet IPv4

Link

HTTP Clientbull Hyper-Text Transfer Protocol

(port 80)bull Request-response protocolbull When

httpwww2hawaiiedu~lipyeowindexhtml is entered into a web browser (http client)

HTTP11 200 OKDate Sun 02 Sep 2012 003540 GMTServer ApacheLast-Modified Tue 21 Aug 2012 012718 GMTETag 7d3e8-2950-4c7bc86e86980Accept-Ranges bytesContent-Length 10576Content-Type texthtmlltDOCTYPE HTML PUBLIC -W3CDTD HTML 40 TransitionalENgt ltHTMLgt

GET ~lipyeowindexhtml HTTP11host www2hawaiiedu

18

Internet Securitybull All data transmitted on the network using the

protocols described thus far are in plaintext

942012 Lipyeow Lim -- University of Hawaii at Manoa

bull Anyone with access to the physical network link can snoop on the bit sequences and decode according to the protocol stack

bull Anyone can read your emails if heshe has access to a link on which your email packets are transmitted

bull Use encrypted connections eg SSLTLS

19

Secure HTTP -- HTTPS

bull Use HTTP over a SSLTLS layer (port 443)bull Negotiate a stateful encrypted connection to carry the

HTTP messagesbull Use a trusted 3rd party (CA) to verify identitybull Use public key handshake to establish a session keybull Encrypt subsequent messages using session key 942012 Lipyeow Lim -- University of Hawaii at Manoa

HTTPSSLTLSTransport TCP

Internet IPv4

Link

HTTPS Server

HTTPSSLTLS

Transport TCP

Internet IPv4

Link

HTTPS Client

Certificate Authority

certificatecertificate

session key

verify certificate verify certificate

HTTP messages

• ICS 101 Fall 2012 Networking and the Internet
• Problem
• LOTR Beacon of Gondor
• Modern Computer Networks
• Local Area Networks
• Data Packet
• Network Abstractions
• TCPIP Four Layer Model
• Link Layer
• Internet Layer
• IPv4 Addresses amp Domain Name Service
• IPv4 amp Inter-network Routing
• Packet Routing Exercise
• Transport Layer
• Applications Email
• Sample Email Header
• Applications HTTP
• Internet Security
• Secure HTTP -- HTTPS

19

Secure HTTP -- HTTPS

bull Use HTTP over a SSLTLS layer (port 443)bull Negotiate a stateful encrypted connection to carry the

HTTP messagesbull Use a trusted 3rd party (CA) to verify identitybull Use public key handshake to establish a session keybull Encrypt subsequent messages using session key 942012 Lipyeow Lim -- University of Hawaii at Manoa

HTTPSSLTLSTransport TCP

Internet IPv4

Link

HTTPS Server

HTTPSSLTLS

Transport TCP

Internet IPv4

Link

HTTPS Client

Certificate Authority

certificatecertificate

session key

verify certificate verify certificate

HTTP messages

• ICS 101 Fall 2012 Networking and the Internet
• Problem
• LOTR Beacon of Gondor
• Modern Computer Networks
• Local Area Networks
• Data Packet
• Network Abstractions
• TCPIP Four Layer Model
• Link Layer
• Internet Layer
• IPv4 Addresses amp Domain Name Service
• IPv4 amp Inter-network Routing
• Packet Routing Exercise
• Transport Layer
• Applications Email
• Sample Email Header
• Applications HTTP
• Internet Security
• Secure HTTP -- HTTPS