CSS434: Parallel

1
CSS490 Message Passing Textbook Ch2 - 3
Instructor Munehiro Fukuda These slides were
compiled from the course textbook, the reference
books, and the instructor痴 original materials.
2
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
3
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釦ime
  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
?
1. Free token
2. Attach
4. Detach
3. busy token
4
Network LayerExample IP
Transportation layer
Datagram
fragmentation
reassembly
Data link layer
Best-effort deliver semantics
Class D for broadcasting
5
Transport LayerExample1 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()
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Transport LayerExample2 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()
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Application LayerExample RSH
Client
Server
inetd
shell
TCP connection request
rshd
Command rsh ls- l
shell
TCP connection Inherited all the way To a child
Command ls -l
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Socket Programming Socket.h
include ltiostreamgt extern "C" include
ltsys/types.hgt // for sockets include
ltsys/socket.hgt include ltnetinet/in.hgt include
ltarpa/inet.hgt include ltnetdb.hgt // for
gethostbyname( ) include ltunistd.hgt // for
close( ) include ltstring.hgt // 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
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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-gth_addr_list ) )
sendSockAddr.sin_port htons( port )
// Open a TCP socket (an Internet strem socket).
if( ( clientFd socket( AF_INET, SOCK_STREAM, 0
) ) lt 0 ) cerr ltlt "Cannot open a client TCP
socket." ltlt endl return NULL_FD //
Connect to the server. while ( connect(
clientFd, (sockaddr)sendSockAddr, sizeof(
sendSockAddr ) ) lt 0 ) // Connected return
clientFd
include "Socket.h" SocketSocket( int port )
port( port ), clientFd( NULL_FD ),
serverFd( NULL_FD ) SocketSocket( )
if ( clientFd ! NULL_FD ) close( clientFd
) if ( serverFd ! NULL_FD ) close(
serverFd ) int SocketgetClientSocket( char
ipName ) // Get the host entry
corresponding to ipName struct hostent host
gethostbyname( ipName ) if( host NULL )
cerr ltlt "Cannot find hostname." ltlt endl
return NULL_FD
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Socket Programming Socket.cpp (Server)
int SocketgetServerSocket( ) 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 ) ) lt
0 ) cerr ltlt "Cannot open a server TCP
socket." ltlt 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_add
r.s_addr htonl( INADDR_ANY )
acceptSockAddr.sin_port htons( port )
if( bind( serverFd, (sockaddr)acceptSockA
ddr, sizeof( acceptSockAddr ) ) lt 0 )
cerr ltlt "Cannot bind the local address to the
server socket." ltlt 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)newSockAd
dr, newSockAddrSize ) ) lt 0 ) cerr ltlt
"Cannot accept from another host." ltlt endl
return NULL_FD return newFd
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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 recvMessageMAXSIZE read(
fd, recvMessage, MAXSIZE ) cout ltlt
recvMessage ltlt endl close( fd )
if ( argc 2 ) // I'm a client if ( (
fd sock.getClientSocket( argv1 ) ) NULL_FD
) return -1 char sendMessageMAXSIZE
cin gtgt sendMessage write( fd,
sendMessage, MAXSIZE ) return 0
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Blocking/Non-Blocking Communication

• Blocking communication
• TCP, UDP, and other communication packages
• Client blocked only when the destination buffer
  is full
• Server blocked if no message has arrived from
  the client.
• Rendezvous
• Client blocked for a server to receive a message
• Server blocked if no message has arrived from
  the client.
• Non-blocking communication
• Server does not want to be blocked when
• It may receive a message from a different client.
• It has another jobs to be done such as
  computation or message transmission.
• Some synchronization is necessary later.

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Synchronization in Non-Blocking Communication

• Polling
• Periodically check if a socket is ready to read
  data
• Example
• sd socket( AF_INET, SOCKET_STREAM, 0)
• set_fl(sd, O_NONBLOCK) // set the socket as
  non-blocking
• struct pollfd pfd
• pfd.fd sd
• poll( pfd, 1, timeout ) // poll the socket
  status
• Interrupt
• Notified from the system when a socket is ready
  to read data
• Example
• sd socket(AF_INET, SOCKET_STREAM, 0)
• signal(SIGIO, sigio_func) // set a future
  interrupt to call sigio_func( )
• fcntl(sd, F_SETOWN, getpid( )) // ask OS to
  deliver this fd interrupt to me
• fcntl(sd, F_SETFL, FASYNC) // set this fd
  asynchronous
• int sigio_func( ) // invoked upon an interrupt
  

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Buffering

• No Buffering
• A message remains on the sender until the
  receiver issues receive( ).
• Rendezvous
• Performance drawback
• Single Message Buffer
• The sender can send at most one message even if
  the receiver has not issued receive( ).
• Stop-and-wait protocol
• A message can be kept read in advance.
• What if the sender has multiple messages?
• Finite-Bound Buffer
• Unsuccessful communication - Go-Back-N Technique
• Flow-controlled communication - sliding window in
  TCP
• Socket capable of changing its buffer size with
  setsockopt( )

message
message
message
message
message
message
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Process Addressing

• Explicit address
• machine id local id
• Example TCP/IP and UDP/IP use IP port
• Demerit No process migration allowed
• machine id local id the last machine id
• Process migration allowed
• Messages forwarded along links to the final
  destination
• Receiver informing sender of its last machine id
• Sender using this info from the following
  messages
• Implicit addressing
• System-wide id (function name)
• Example RPC
• Name server required

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Failure Handling

• Loss of request message
• Loss of response message
• Unsuccessful execution of request
• Do we really need acknowledgment messages?

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Idempotency
server
server
client

• A pair of request and response is enough to
  handle faults
• Idempotency assumed
• At-least one semantics
• Last-one semantics

client
request
Timeout
request
request 2
Timeout
response
request 3
Timeout
response
request 4
reesponse 2
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Exactly-One Semantics

• What if errors in the banking system
• New semantics required
• Exactly-one semantics
• Server must keep track of the request sequence

Withdraw 100
Withdraw995 100
1000-100 900
1000-100 900 for Trans995
Not received
Not received
Withdraw 100
Withdraw995 100
Trans995 completed No subtraction
900-100 800!
100 received
100 received
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Exercises (No turn-in)

1. Why do we need layered network protocols?
2. When implementing TCP with datagram, what do we
   have to take care of?
3. Consider the pros and cons of polling and
   interrupt in non-blocking communication.
4. Consider an example inducing an accidental system
   hang-up (named a deadlock) in no-buffering
   communication.
5. Which of the following operations are idempotent?
6. cin gtgt data
7. ifstream infile(妬nput.txt