Software Engineering in Geomatics

.

...... Software Engineering in Geomatics

Dražen OdobašićMario Miler

Faculty of Geodesy, University of Zagreb

Zagreb, March 12, 2012

Software Engineering in GeomaticsExercise 1

Internet

What is the Internet?

.Definition..

......

The Internet is a global system of interconnected computernetworks that use the standard Internet protocol suite to servebillions of users worldwide.

Google, Facebook, E-Mail, File transfer, …HTTP, SMTP, FTP, BitTorrent, SCP, …

Software Engineering in GeomaticsExercise 1

Internet

What is the Internet?

originated 1969 within U.S. Defense Department programcalled ARPANET (Advanced Research Projects AgencyNetwork)1970. newsgroups, buletin-board systems1982-83. TCP/IP adopted as standard1986. 10 000 hosts connected to the Internet1988. IRC - Internet relay chat1990. HTTP (World Wide Web), Mosaic browser1995. Yahoo1996. Google1997. 10 000 000 hosts (100% growth per year)2001. Wikipedia2004. Facebook2012. ?

Software Engineering in GeomaticsExercise 1

Internet protocols

TCP/IP protocol suite (1)

.Simplification..

......

Data are split into datagrams (packets) which are transferredbetween two hosts connected to the internet.

Transfer is routed through different network nodes, and for eachpacket we get confirmation if packet was received. Droppedpackets are retransmitted.

Data are reconstructed on host.

Software Engineering in GeomaticsExercise 1

Internet protocols

TCP/IP protocol suite (2)

Layer concept (RFC 1122)1:...1 Link

PPP, PPPoE, DSL, ISDN, …...2 Internet

IP, ICMP, IPsec, …...3 Transport

TCP, UDP, RIP, …...4 Application

HTTP, FTP, BitTorrent, DNS, SMTP, …

1https://tools.ietf.org/html/rfc1122

Software Engineering in GeomaticsExercise 1

Internet protocols

TCP/IP protocol suite (3)

Software Engineering in GeomaticsExercise 1

Internet protocols

IP protocol (1)

.Task..

......of delivering datagrams from the source host to the destinationhost solely based on the addresses

.IP Address..

......

is a numerical label assigned to each device (e.g., computer,printer) participating in a computer network that uses the InternetProtocol for communication

Software Engineering in GeomaticsExercise 1

Internet protocols

IP protocol (2)

Datagramheader

contains all the information sufficient for routing from theorigin to the destination

payloaddata, usually 1.5Kb

IP uses different datagrams for different purposes.

Software Engineering in GeomaticsExercise 1

Internet protocols

IP protocol (3)

IPv432bit (4 294 967 296)

172.16.254.1four 8bit blocks, range 0-255 (dec)

0.0.0.0 ⇒ 255.255.255.255

reserved private IP range10.0.0.0 - 10.255.255.255 ⇒ 16 777 216 (24bits)172.16.0.0 – 172.31.255.255 ⇒ 1 048 576 (20bits)192.168.0.0 – 192.168.255.255 ⇒ 65 536 (16bits)

special localhost range: 127.0.0.0 – 127.255.255.255last public block exhausted February 3, 2011, still in use(NAT)

Software Engineering in GeomaticsExercise 1

Internet protocols

IP protocol (4)

IPv6128bit (3.403×1038)

FE80:0000:0000:0000:0202:B3FF:FE1E:8329eight 16bit blocks, range 0000-FFFF (hex)

0000:0000:0000:0000:0000:0000:0000:0000 ⇒FFFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF

future...

Software Engineering in GeomaticsExercise 1

Internet protocols

IP protocol (5)

Software Engineering in GeomaticsExercise 1

Internet protocols

TCP protocol (1)

.Transmission Control Protocol..

......

reliable stream delivery service that guarantees delivery of a datastream sent from one host to another without duplication or losingdata.

IP handles actual delivery of the data, TCP keeps track of theindividual units of data transmission, called segments, that amessage is divided into for efficient routing through the network.

Even though every packet has the same destination address, theycan be routed on different paths through the network. When theclient program on the destination computer receives them, the TCPreassembles the individual segments and ensures they are correctlyordered and error free as it streams them to an application.

Software Engineering in GeomaticsExercise 1

Internet protocols

TCP protocol (2)

Ordered data transferthe destination host rearranges according to sequence number

Retransmission of lost packetsany cumulative stream not acknowledged is retransmitted

Error-free data transfereach packet has a checksum to assure correctness

Flow controllimits the rate a sender transfers data to guarantee reliabledelivery

Congestion controlmechanisms control the rate of data entering the network,keeping the data flow below a rate that would trigger collapse

Software Engineering in GeomaticsExercise 1

Internet protocols

Application layer protocols

HTTPHypertext Transfer ProtocolTHE Internet, more detail later

DNSDomain Name Systemtranslates queries for domain names (which are meaningful tohumans) into IP addresses for the purpose of locatingcomputer services and devices worldwidewww.google.hr ⇒ 209.85.148.94

FTP/NNTP/SMTP/…File Transfer Protocol/Network News TransferProtocol/Simple Mail Transfer Protocol/…

Software Engineering in GeomaticsExercise 1

Internet protocols

DNS (1)

.Domain Name System..

......

is a hierarchical distributed naming system for computers,services, or any resource connected to the Internet or a privatenetwork.Domain name..

......is an identification string that defines a realm of administrativeautonomy, authority, or control in the Internet

Software Engineering in GeomaticsExercise 1

Internet protocols

DNS (2)

Top-level domains names:ccTLD - coutry-code top-level domains

.hr, .de, .ru, .us, .cn, .yp, .ly, .tk, .to, .me, …gTLD - generic top-level domains

.org, .net, .com, .edu, .info, .mobi, .mil, …

Management of most top-level domains is delegated toresponsible organizations by the Internet Corporation forAssigned Names and Numbers (ICANN)

Software Engineering in GeomaticsExercise 1

Internet protocols

DNS (3)

Fully qualified domain name (FQDN):www.geof.unizg.hr

TLD ⇒ hrsubdomain ⇒ unizgsubdomain ⇒ geofhost ⇒ www

kartolog.geoinfo.geof.hrwww.facebook.com

Software Engineering in GeomaticsExercise 1

Internet protocols

DNS (4)

Everyone can register a domain, usually paying a yearly fee(depends on a provider):

Example: one_day_i_will_rule_the_world (www.orbis.hr):.com – 11€.net – 11€.org – 11€.hr – 69€.name – 8,26€.eu – 11,90€.me – 51,44€.si – 25,25€.xxx – 89€

Software Engineering in GeomaticsExercise 1

Exercise

EX: Setup

standard Linux/Windows installationwe prefer command line toolsmost tools are already available, other tools/libraries will beinstalled along the wayEveryone knows how to get to command line ?

Software Engineering in GeomaticsExercise 1

Exercise

EX: Basic network tools (1)

PING - used to determine latency (round-trip) between systemsand networks

ping -n 3 www.facebook.com

Pinging www.facebook.com [69.171.242.12] with 32 bytes of data:

Reply from 69.171.242.12: bytes=32 time=112ms TTL=127Reply from 69.171.242.12: bytes=32 time=112ms TTL=127Reply from 69.171.242.12: bytes=32 time=110ms TTL=127

Ping statistics for 69.171.242.12:Packets: Sent = 3, Received = 3, Lost = 0 (0% loss),

Approximate round trip times in milli-seconds:Minimum = 110ms, Maximum = 112ms, Average = 111ms

Software Engineering in GeomaticsExercise 1

Exercise

EX: Basic network tools (2)

TRACEROUTE - used to show all hops between two hosts

tracert -d www.facebook.com

Tracing route to www.facebook.com [31.13.72.20]over a maximum of 30 hops:

1 <1 ms <1 ms <1 ms 10.0.2.22 80 ms 99 ms 99 ms 192.168.1.13 * * * Request timed out.4 19 ms 18 ms 18 ms 172.29.16.1295 26 ms 25 ms 26 ms 213.248.88.217

...

...10 58 ms 57 ms 58 ms 213.248.92.22211 79 ms 60 ms 57 ms 204.15.22.11112 57 ms 59 ms 57 ms 31.13.25.15713 58 ms 58 ms 57 ms 31.13.72.20

Trace complete.

Software Engineering in GeomaticsExercise 1

Exercise

Assignments

Choose 5 web sites you regularly visit, and for each site:...1 identify domain parts (1 point)...2 determine average ping response (1 point)...3 use traceroute to determine IP addresses of hosts between you

and your destination (2 points)...4 BONUS: geolocate tracerouted IPs using

http://geoiptool.com/ or some other service (2 points)Send completed assignments to nastava@geoinfo.geof.hr