CSS434 Networking Textbook Ch3

1. CSS434 Networking Textbook Ch3 Professor: Munehiro Fukuda CSS434 Networking

2. Outline • OSI 7 layers • Physical/data link layers (layer 1 & 2) • Network layer – IP (layer 3) • Transport layer – TCP UDP (layer 4) • Application layer – RSH (layer 7) • Socket examples CSS434 Networking

3. OSI 7 Layers Site A Site B Application protocol 7 Application rsh, ftp, Telnet Application Presentation protocol Presentation 6 Dealing with heterogeneity And cryptography Presentation Session protocol 5 Session Dialog control (rarely supported) Session Transport protocol Transport 4 UDP, TCP Transport Network protocol Network Network 3 IP Data link protocol IEEE802.2 connection or connectionless Data link Data link 2 Ethernet Physical protocol Physical 1 Physical Network CSS434 Networking

4. Layer Description Examples Application Protocols that are designed to meet the communication requirements of FTP HTTP, , SMTP, specific applications, often defining the interface to a service. CORBA IIOP Presentation Protocols at this level transmit data in a network representation that is Secure Sockets independent of the representations used in individual computers, which may ( SSL),CORBA Data differ. Encryption is also performed in this layer, if required. Rep. Session At this level reliability and adaptation are performed, such as detection of failures and automatic recovery. Transport This is the lowest level at which messages (rather than packets) are handled. TCP, UDP Messages are addressed to communication ports attached to processes, Protocols in this layer may be connection-oriented or connectionless. Network Transfers data packets between computers in a specific network. In a WAN IP, ATM virtual or an internetwork this involves the generation of a route passing through circuits routers. In a single LAN no routing is required. Data link Responsible for transmission of packets between nodes that are directly Ethernet MAC, connected by a physical link. In a WAN transmission is between pairs of ATM cell transfer, routers or between routers and hosts. In a LAN it is between any pair of hosts. PPP Physical The circuits and hardware that drive the network. It transmits sequences of Ethernet base- band binary data by analogue signalling, using amplitude or frequency modulation signalling, ISDN of electrical signals (on cable circuits), light signals (on fibre optic circuits) or other electromagnetic signals (on radio and microwave circuits). OSI Protocol Summary CSS434 Networking

5. Physical/Data Link LayerExample: CSMA/CD and Token Ring • IEEE802.3: CSMA/CD (Carrier sense multiple access with collision detection) • Listening to the shared medium • Transmitting a data packet • Detecting collision on the medium • Deferring and retransmitting a packet in 2k–time base collision window • IEEE802.5: Token Ring • Receiving a free token from my (left) neighbor • Attaching a data packet to the token • Forwarding the token to my (right) neighbor • Detaching a packet from the token if it is addressed here 1 listen 3. detect 2 transmit Ⅹ 1. Free token 2. Attach 4. Detach 3. busy token CSS434 Networking

6. Class A Octet 2 – 4 (1,677,716) Octet 1 0-127 0 Net # Host # Net # Host # 1 0 S S D D L L 1 1 0 Net # Host# Class B IP packet ID and size IP packet ID and size Destination IP address Destination IP address Octet 1 128-191 Octet 3 – 4 (65,536) Octet 2 Source IP address Source IP address Class C Octet 4 (256) Octet 1 128-191 Octet 2 – 3 Network LayerExample: IP Transportation layer Datagram fragmentation reassembly Data link layer Best-effort deliver semantics Class D: for broadcasting CSS434 Networking

7. Transport Layer:Example1: UDP • User Datagram Protocol • Connectionless • May be lost • No FIFO order • Multicast feature • Unix datagram • Example: TFTP, rwho client server socket() socket() Create a sock descriptor bind() bind() Bind it to an IP address recvfrom() sendto() Blocks until data received sendto() recvfrom() CSS434 Networking

8. Transport Layer:Example2: TCP client server • Transport Control Protocol • Connection-oriented • Reliable • FIFO order • No Multicast feature • Unix stream socket • Example: ftp, http, rsh all major applications socket() socket() Create a sock descriptor bind() Bind it to an IP address liseten() Declare this is connection-oriented accept() Wait for a connection Connection established connect() Blocks until connection established read() write() read() wrte() CSS434 Networking

9. Application LayerExample: RSH Client Server inetd shell TCP connection request Command rsh ls- l rshd shell TCP connection Inherited all the way To a child Command ls -l CSS434 Networking

10. Message Layers Application Messages (UDP) or Streams (TCP) Transport UDP or TCP packets Internet IP datagrams Network interface Network-specific frames Underlying network Summary of TCP/IP Layers CSS434 Networking

11. Socket Programming: Socket.h #include <iostream> extern "C" { #include <sys/types.h> // for sockets #include <sys/socket.h> #include <netinet/in.h> #include <arpa/inet.h> #include <netdb.h> // for gethostbyname( ) #include <unistd.h> // for close( ) #include <string.h> // for bzero( ) } #define NULL_FD -1 #define MAXSIZE 20 class Socket { public: Socket( int ); ~Socket( ); int getClientSocket( char[] ); int getServerSocket( ); private: int port; int clientFd; int serverFd; }; CSS434 Networking

12. Socket Programming: Socket.cpp (Client) // Fill in the structure "sendSockAddr" with the server address. sockaddr_in sendSockAddr; bzero( (char*)&sendSockAddr, sizeof( sendSockAddr ) ); sendSockAddr.sin_family = AF_INET; //Address Family Internet sendSockAddr.sin_addr.s_addr = inet_addr( inet_ntoa( *(struct in_addr*)*host->h_addr_list ) ); sendSockAddr.sin_port = htons( port ); // Open a TCP socket (an Internet strem socket). if( ( clientFd = socket( AF_INET, SOCK_STREAM, 0 ) ) < 0 ) { cerr << "Cannot open a client TCP socket." << endl; return NULL_FD; } // Connect to the server. while ( connect( clientFd, (sockaddr*)&sendSockAddr, sizeof( sendSockAddr ) ) < 0 ); // Connected return clientFd; } #include "Socket.h" Socket::Socket( int port ) : port( port ), clientFd( NULL_FD ), serverFd( NULL_FD ) { } Socket::~Socket( ) { if ( clientFd != NULL_FD ) close( clientFd ); if ( serverFd != NULL_FD ) close( serverFd ); } int Socket::getClientSocket( char ipName[] ) { // Get the host entry corresponding to ipName struct hostent* host = gethostbyname( ipName ); if( host == NULL ) { cerr << "Cannot find hostname." << endl; return NULL_FD; } CSS434 Networking

13. Socket Programming: Socket.cpp (Server) int Socket::getServerSocket( ) { if ( serverFd == NULL_FD ) { // Server not ready sockaddr_in acceptSockAddr; // Open a TCP socket (an internet stream socket). if( ( serverFd = socket( AF_INET, SOCK_STREAM, 0 ) ) < 0 ) { cerr << "Cannot open a server TCP socket." << endl; return NULL_FD; } // Bind our local address so that the client can send to us bzero( (char*)&acceptSockAddr, sizeof( acceptSockAddr ) ); acceptSockAddr.sin_family = AF_INET; // Address Family Internet acceptSockAddr.sin_addr.s_addr = htonl( INADDR_ANY ); acceptSockAddr.sin_port = htons( port ); if( bind( serverFd, (sockaddr*)&acceptSockAddr, sizeof( acceptSockAddr ) ) < 0 ) { cerr << "Cannot bind the local address to the server socket." << endl; return NULL_FD; } listen( serverFd, 5 ); } // Read to accept new requests int newFd = NULL_FD; sockaddr_in newSockAddr; socklen_t newSockAddrSize = sizeof( newSockAddr ); if( ( newFd = accept( serverFd, (sockaddr*)&newSockAddr, &newSockAddrSize ) ) < 0 ) { cerr << "Cannot accept from another host." << endl; return NULL_FD; } return newFd; } CSS434 Networking

14. Socket Programming: Main #include "Socket.h" #define PORT 10000 // You are given a specific pot from the instructor int main( int argc, char *argv[] ) { Socket sock( PORT ); int fd; if ( argc == 1 ) { // I'm a server while ( true ) { if ( ( fd = sock.getServerSocket( ) ) == NULL_FD ) return -1; char recvMessage[MAXSIZE]; read( fd, recvMessage, MAXSIZE ); cout << recvMessage << endl; close( fd ); } } if ( argc == 2 ) { // I'm a client if ( ( fd = sock.getClientSocket( argv[1] ) ) == NULL_FD ) return -1; char sendMessage[MAXSIZE]; cin >> sendMessage; write( fd, sendMessage, MAXSIZE ); } return 0; } CSS434 Networking

15. Exercises (No turn-in) • Why do we need layered network protocols? • When implementing TCP with datagram, what do we have to take care of? • Compare UDP and TCP for the implementation of each of the following application-level or presentation-level protocols (textbook p142, Q3.7): • Telnet • FTP • Rwho, finger • HTTP • RPC or RMI CSS434 Networking