Practical Session 10

1. Practical Session 10 IP (Internet Protocol) Address TCP/IP Model DNS Ports Sockets TCP UDP Client-Server Model Text Transfer HTTP Protocol

2. Internet Protocol • What is protocol? • נוהל, רשימת כללים לביצועה של פעילות מסוימת • What is internet protocol? • A protocol that details how data is sent and received over the internet network. • What is Internet? • It is a global system of interconnected computer networks. • The internet is basically a network of networks. • How a machine is identified? • Every machine wishes to connect to the Internet, receives an IP address. • IP address is a unique identifier for the machine.

4. What about Israel?

5. Bezeq InternationalLine

6. Tamares Internet Line

7. IP Address • IPv4: • 32bit of size • Format: XXX.XXX.XXX.XXX • Where XXX is a number from 0 to 255 • Each block is 8bit. • Allows 232 unique addresses (≈ 4.3billion addresses). • Examples: • 192.115.80.66 – IP address of ynet • 209.85.147.147 – IP address of google • 132.72.41.239 – IP address of www.cs.bgu.ac.il • IPv6: • 128bit of size • Format: • XXXX.XXXX.XXXX.XXXX.XXXX.XXXX.XXXX.XXXX • Where each XXXX consist of a hexadecimal value. 0…9, A..F • Examples: • 2001:4860:0000:1001:0000:0000:0000:0068:– IPv6 of ipv6.google.com • 2620:0000:1CFE:FACE:B00C:0000:0000:0003 – IPv6 of www.v6.facebook.com • Allows 2128 unique addresses.

8. IP Addresses Utilization

10. Domain Name System • DNS: Domain Name System • DNS maps domain names to IPs. • Example: • Domain name: www.cs.bgu.ac.il • IP: 132.72.41.239 • Why DNS? • Machines understand numbers only. • Humans find it hard to remember numbers. • Thus, DNS was invented. • DNS Servers are found at: • Each ISP has its own DNS server. Normally two separate servers. (Primary DNS/Secondary DNS) • There are 13 root servers in the world.

11. Root DNS Server Map

12. Communication Model

13. Tracing an Israeli Website • Tracing route to haaretz.co.il [192.118.72.27] • over a maximum of 30 hops: • 1 <1 ms <1 ms <1 ms BEZEQ [10.0.0.138] [My Router] • 2 20 ms 19 ms 19 ms 213.57.0.7 [Yakum – Israel] • 3 19 ms 19 ms 19 ms tbd.pt.mx-ipsla.con.hotnet.net.il [213.57.0.221] [Yakum – Israel] • 4 21 ms 20 ms 20 ms ae7.50.hfa.mx-mx.con.hotnet.net.il [213.57.0.250] [Yakum – Israel] • 5 91 ms 23 ms 23 ms 82.166.25.214.fix.netvision.net.il [82.166.25.214] [Haifa – Israel] • 6 23 ms 22 ms 23 ms core1-edge1-clr.nta.nv.net.il [212.143.203.57] [Haifa – Israel] • 7 23 ms 22 ms 23 ms coresw1-ptk-3-6-core1.nta.nv.net.il [212.143.203.85] [Haifa – Israel] • 8 25 ms 25 ms 25 ms212.143.29.193 [Haifa – Israel] • 9 25 ms 26 ms 26 ms212.143.29.196 [Haifa – Israel] • 10 * 33 ms 33 ms 192.118.72.66 [Ramat Gan – Israel] • 11 27 ms 27 ms 27 ms 192.118.72.27 [Ramat Gan – Israel] • Trace complete.

14. Two Different ISPs– One Website • Will the tracing results be the same?

15. Tracing heathcare.gov via HotNet • Tracing route to healthcare.gov [23.35.119.205] • over a maximum of 30 hops: • 1 <1 ms <1 ms <1 ms BEZEQ [10.0.0.138] [My Router] • 2 19 ms 19 ms 19 ms 213.57.0.7 [Tel Aviv - Israel] • 3 20 ms 19 ms 19 ms tbd.pt.mx-ipsla.con.hotnet.net.il [213.57.0.221] [Tel Aviv - Israel] • 4 21 ms 21 ms 21 ms ae0.hfa.mx-mx.con.hotnet.net.il [213.57.3.246] [Tel Aviv - Israel] • 5 71 ms 71 ms 71 ms core-213-57-3-186.ptr.hotnet.net.il [213.57.3.186] [Tel Aviv - Israel] • 6 102 ms 101 ms 99 ms r1fra1.core.init7.net [80.81.192.67] [Frankfurt - Germany] • 7 91 ms 229 ms 95 ms r1par1.core.init7.net [77.109.140.149] [Zurich - Switzerland] • 8 92 ms 85 ms 84 ms gw-akamai.par1.init7.net [77.109.134.254] [Thun - Switzerland] • 9 98 ms 90 ms 96 ms a23-35-119-205.deploy.static.akamaitechnologies.com [23.35.119.205] [Cambridge - USA] • Trace complete.

16. Tracing heathcare.gov via Golan Telecom • Tracing route to healthcare.gov [172.229.199.205] • over a maximum of 30 hops: • 1 1 ms 1 ms 2 ms 192.168.43.1 [GT Internal Network] • 2 1477 ms 74 ms 100 ms 10.224.235.78 [GT Internal Network] • 3 1838 ms 528 ms 61 ms 10.224.224.101 [GT Internal Network] • 4 826 ms 75 ms 64 ms 10.224.224.102 [GT Internal Network] • 5 38 ms 37 ms 36 ms 37.26.146.1 [Tel Aviv - Israel • 6 34 ms 35 ms 38 ms bzq-218-111-9.red.bezeqint.net [81.218.111.9] [Tel Aviv - Israel • 7 40 ms 44 ms 42 ms bzq-179-162-69.static.bezeqint.net [212.179.162.69] [Tel Aviv - Israel] • 8 * 37 ms 39 ms bzq-219-189-94.cablep.bezeqint.net [62.219.189.94] [Tel Aviv - Israel] • 9 93 ms 99 ms 89 ms 213.242.116.129 [France] • 10 * * 163 ms ae-15-15.ebr1.Frankfurt1.Level3.net [4.69.143.246] [Frankfurt - Germany] • 11 124 ms 90 ms 318 ms ae-74-74.csw2.Frankfurt1.Level3.net [4.69.163.22] [Frankfurt - Germany] • 12 135 ms 89 ms 114 ms ae-2-70.edge5.Frankfurt1.Level3.net [4.69.154.73] [Frankfurt - Germany] • 13 284 ms 90 ms 317 ms xe-10-2-1.fra44.ip4.tinet.net [141.136.102.73] [France] • 14 98 ms 100 ms 98 ms xe-9-0-0.ams20.ip4.tinet.net [89.149.183.98] [Amsterdam - Netherlands] • 15 99 ms 109 ms 95 ms akamai-gw.ip4.tinet.net [141.136.99.6] [France] • 16 220 ms 108 ms 106 ms a172-229-199-205.deploy.static.akamaitechnologies.com [172.229.199.205] [Cambridge - USA] • Trace complete.

17. Tracing an Australian address • Tracing route to neoaustralia.com.au [202.148.129.157] • 1 <1 ms <1 ms <1 ms BEZEQ [10.0.0.138] [My Router] • 2 19 ms 19 ms 19 ms 213.57.0.7 [Yakum - Israel] • 3 20 ms 19 ms 20 ms tbd.pt.mx-ipsla.con.hotnet.net.il [213.57.0.221] [Yakum - Israel] • 4 41 ms 41 ms 42 ms ge3-0.catania4.cat.seabone.net [93.186.129.130] [Catania - Italy] • 5 80 ms 80 ms 81 ms xe-11-1-0.franco31.fra.seabone.net [89.221.34.183] [Roma - Italy] • 6 94 ms 95 ms 94 ms ffm-b12-link.telia.net [213.248.68.189] [Frankfurt Am Main - Germany] • 7 95 ms 94 ms 94 ms ffm-bb1-link.telia.net [213.155.135.8] [Frankfurt Am Main - Germany] • 8 188 ms 186 ms 185 ms nyk-bb1-link.telia.net [213.155.131.145] [New York (New York) - USA] • 9 248 ms 251 ms 248 ms las-bb1-link.telia.net [80.91.251.252] [Las Vegas (Nevada)- USA] • 10 257 ms 254 ms 262 ms las-b3-link.telia.net [213.155.130.127] [Las Vegas (Nevada)- USA] • 11 250 ms 246 ms 250 ms singaporetelecom-ic-150846-las-b3.c.telia.net [80.239.167.194] [Los Angeles - California] • 12 246 ms 350 ms 255 ms 203.208.171.141 [Singapore - Singapore] • 13 409 ms 409 ms 400 ms 203.208.174.50 [Singapore - Singapore] • 14 * * * Request timed out. [Firewall] • 15 * * * Request timed out. [Firewall] • 16 * * * Request timed out. [Firewall] • 17 * * 423 ms 59.154.57.190 [Pennant Hills (New South Wales) - Australia] • 18 410 ms 418 ms 407 ms 59.154.57.188 [Pennant Hills (New South Wales) - Australia] • 19 419 ms 410 ms 414 ms 119.225.61.94 [Brisbane (Queensland) - Australia] • 20 420 ms 416 ms 420 ms po93.mls1.bne3.server-noc.com [203.147.255.189] [Wickham - Australia] • 21 425 ms 407 ms 418 ms po93.mls1.bne3.server-noc.com [203.147.255.189] [Wickham - Australia] • 22 409 ms 420 ms 421 ms www.bathurstmowerland.com [202.148.129.157] [Wickham - Australia] • Trace complete.

18. TCP/IP Model • Application Layer • Communication between applications • Protocols: • FTP – File Transfer Protocol • SMTP – Simple Mail Transfer Protocol • HTTP – Hyper Text Transfer Protocol • BitTorrent– Peer-to-Peer file sharing protocol • Transport Layer • Communication between end-to-end machines. • Protocols: • TCP – Transmission Control Protocol • UDP – User Datagram Protocol • SCTP – Stream Control Transfer Protocol • Internet Layer • Routing: Handles the way packets are sent from end machine A to end machine B. • Decides which path the packet needs to take in order to be received at destination. • IP – Internet Protocol • Link Layer (Network Access Layer) • Move packets between the interfaces of two different hosts on the same link. • Protocol: • MAC – Media Access Control. • Physical Layer • The pure hardware in any network infrastructure through it we send our bits of data. • The Ethernet cables, communication satellites, copper lines, etc.

19. TCP in TCP/IP • TCP/IP is the communication protocol for communication between computers on the Internet. • TCP/IP stands for Transmission Control Protocol / Internet Protocol. • Using this model we can transfer data between two different machines. • Examples of TCP uses: • Web surfing using browsers. • File download using the browser. • Sending emails. • FTP Download

20. TCP in TCP/IP • TCP is used for communication between applications. • If application A wants to communicate with application B via TCP: • A sends a communication request, called “handshake”. • This request must be sent to an exact address. • B accepts request. • After the handshake between the two applications, TCP will set up a full-duplex communication between the two applications. • Then both ends can send and receive data. • This communication stays until one of the application closes the connection. • Full-duplex communication: • A can send to B. • B can send to A.

21. Ports • What are ports? • Think of them as entry/exit points to/from a machine. • Why ports? • Allows more than one service to be accessible at the same time on one machine. • Each port has a unique number: • HTTP uses port 80. (as default) • FTP uses port 21. (as default) • There are 64K (65536) ports to use. (from 1 to 65536) • Example: • http://15.216.110.22:80/ • ftp://15.216.110.22:21/

22. Sockets • What? • A socket is an endpoint for communication between two machines. • An instance can be created by the application, and used in order transfer and receive data. • Socket Types: • Stream Sockets – TCP • Datagram Sockets – UDP • Raw Sockets – ICMP (access to a lower layer protocol like IP) • Java API: • http://docs.oracle.com/javase/1.4.2/docs/api/java/net/Socket.html

23. Stream Sockets • Stream sockets are used by the Transmission Control Protocol (TCP). • Definition: • Client Socket: • Socket clientSocket = new Socket(InetAddress address, int port); • Address – server IP address. • Port – port of server. • Server Socket: • Socket serverSocket = new ServerSocket(int port); • Port – port of server. • Socket clientConnection = serverSocket.accept(); • Waits for a new connection. • Returns a Socket object once connected. • Using this new object, communication is done.

24. Stream Sockets 2. Client connects to the server using a socket with the host/ip and the port of the server. - A local port is assigned that will be used to connect to the client. Server listens at port 4444 3. the server gets a new socket bound to the same local port and also has its remote endpoint set to the address and port of the client. It needs a new socket so that it can continue to listen to the original socket for connection requests while tending to the needs of the connected client.

25. Notes on Sockets • Can create more than one client socket with the same host and port! • Can create only one ServerSocket with a certain port! • Cannot create a ServerSocket on a local port used by another socket.

26. Transmission Control Protocol • TCP: • Connection oriented protocol; a connection must be established between two sockets before transferring data: • Socket A listens to a port. • Socket B connects to socket A using IP:PORT. • Data can be sent in either way. • Connection is closed. • TCP Properties: • Advantages: • Data sent is guaranteed to be correct. • Data sent is guaranteed to be sent in full. • Data sent is guaranteed to be received in same order sent. • Disadvantages: • Latency (lag) introduced by waiting for acknowledgements. • Overhead makes the transmission slower. • Overhead: All the extra data sent by the communication protocol, excluding the real data we wish to send.

27. TCP Frame Structure

28. TCP 3-Way Handshake Diagram • Host A sends a TCP SYNchronize packet to Host B • Host B receives A's SYN • Host B sends a SYNchronize-ACKnowledgement • Host A receives B's SYN-ACK • Host A sendsACKnowledge • Host B receives ACK. TCP socket connection is ESTABLISHED.

29. UDP- User Datagram Protocol • UDP: • No connection between sockets required! • Application A can send any data at any time without prior notification. • UDP Properties: • No guarantee on packet order. • No guarantee if packet is received. • If a packet received is corrupt, then it is discarded. • UDP Advantages: • Great for streaming live media (video, music). • Faster transmission due to smaller overhead. • UDP is used by: • DNS • DHCP • Any Time-sensitive application.

30. UDP Frame Structure

31. The Client-Server Model • A widely used model consisting of: • Server • Clients • Server: • Provides a service of some kind. • Examples: Web Server, FTP Server, DNS Server • Clients: • Connect to the server requesting the service. • Establishing connection: • The Server awaits connections. (listens to a port) • The server reacts to clients requests. • Example: • SimpleLinePrinter (TCP server-client: server accepts one client receives msgs from it- “bye” for termination)

32. Running netstat –p when both the client and server are on the same machine should show:

33. Text Transfer In Java • Reading data from Socket: • Reader Object: • BufferedReaderbufferedReader = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()), “UTF-8”); • Reading Line: • String line = bufferedReader.readLine(); • Writing data to socket: • Writer Object: • PrintWriterprintWriter = new PrintWriter(new OutputStreamWriter(clientSocket.getOutputStream(), "UTF-8"), true); • Writing Line: • printWriter.print(“my text message”); • printWriter.flush(); • http://docs.oracle.com/javase/tutorial/networking/sockets/readingWriting.html

34. Text Encoding • Different computers may use different symbol representations. Text sent might be received and understood differently. • Example: • Sending text from Linux Windows operating systems. • New line in Linux: \n • New line in Windows: \r\n • In order to ensure that the text sent is received correctly, both clients and server need to agree on text format. • Encoding formats example: • UTF-8 • ANSI • UCS-2

35. Examples • in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream(),"UTF-8")); • out = new PrintWriter(new OutputStreamWriter(clientSocket.getOutputStream(), "UTF-8"), true); • Code Examples: • 02_Echo(server sends back the messages that the client sends – UTF-8 format)

36. Protocol Interface • We don’t want to hold the implementation of a protocol inside the server’s code.  • Protocol: • How to send messages • How to end transmission etc. • define an interface ServerProtocol • process() - for processing the received message and construct a response message • isEnd() - identifies the end of a protocol • Example: • 03_ProtocolInterface (server sends messages and checks for end of transmission using a protocol- sends numbered messages).

37. HTTP • Hypertext Transfer Protocol • HTTP is the protocol to exchange or transfer hypertext. • Hypertext is text with references (hyperlinks) to other text that the reader can immediately access. • Create a socket to the host with port 80 and sent the HTTP request through it.

38. HTTP - Request • An HTTP request is defined as a header, followed by an empty line and an optional body. • The request includes the protocol version. • Example: • Get Request: GET /index.html HTTP/1.1 Host: www.example.com

39. HTTP Response • An HTTP response is defined as a header, followed by an empty line and an optional body. • Example: • 04_http (send a get request using HTTP protocol)

40. Network console tools • ipconfig (Microsoft Windows console application) – displays all current TCP/IP network configuration values. • ifconfig (Unix-like console application) - configure, control, and query TCP/IP network interface parameters. • ping (Unix-like & Windows) - utility used to test whether a particular host is reachable across an Internet Protocol (IP) network and to measure the round-trip time for packets sent from the local host to a destination computer. • Telnet client (Unix-like & Windows) - Telnet is a network protocol used to provide a bidirectional interactive communications facility. Typically, telnet provides access to a command-line interface on a remote host via a virtual terminal connection. Putty can be used on recent Windows-es which don't have telnet. • cURL is a computer software project providing a library and command-line tool for transferring data using various protocols.