CS 145A Implementation Issues

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CS 145AImplementation Issues

• Netlab.caltech.edu/course

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Topics of this thread

• How does the TCP/IP work? (roughly)
• (Very) Simple basic tools on network
  engineering
• Design and implementation of protocols

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Mail lists

• CS145class.cs.caltech.edu
• CS145ta.cs.caltech.edu

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Today

• The topology of Internet
• Naming
• Packet transmission
• Stream Connection

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What does the Internet look like?

• Example (/sbin/traceroute)
• C\gttracert cwis.usc.edu
• Tracing route to cwis.usc.edu 128.125.253.146
• 1 lt1 ms Jorgensen-RSM-44.caltech.edu
  131.215.44.253
• 2 lt1 ms Booth-border.ilan.caltech.edu
  131.215.254.254
• 3 lt1 ms CalREN-Caltech.caltech.edu
  192.41.208.49
• 4 lt1 ms JPL--CIT.POS.calren2.net
  198.32.248.5
• 5 1 ms UCLA--JPL.POS.calren2.net
  198.32.248.1
• 6 1 ms ISI--UCLA.POS.calren2.net
  198.32.248.29
• 7 2 ms USC--ISI.POS.calren2.net
  198.32.248.25
• 8 3 ms rtr43-c2-gw.usc.edu
  128.125.251.66
• 9 2 ms rtr-gw-1.usc.edu 128.125.254.1
• 10 2 ms cwis.usc.edu 128.125.253.146

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Topology of the Network
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Global Network (From Quest)
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Get your IDs on-line

• Example (/sbin/ifconfig)
• C\gtipconfig all
• Physical Address. . . . . . . . .
  00-10-A4-79-F0-32
• IP Address. . . . . . . . . . . .
  131.215.44.214
• Subnet Mask . . . . . . . . . . . 255.255.255.0

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Use of the IDs
Application
TCP/UDP
IP
MAC
Physic
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The Journey of a packet (1)131.215.44.214
Application 131.215.44.214 Send MSG to 128.125.253.146 5001
UDP
IP
MAC
Physic
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The Journey of a packet (1)131.215.44.214
Application 131.215.44.214 Send MSG to 128.125.253.146 5001
UDP UDP header MSG Send to 128.125.253.146
IP
MAC
Physic
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The Journey of a packet (1)131.215.44.214
Application 131.215.44.214 Send MSG to 128.125.253.146 5001
UDP UDP header MSG Send to 128.125.253.146
IP IP header UDP header MSG Send to 131.215.44.253 (from routing table) Send to 00906DE7D400 (from ARP)
MAC
Physic
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The Journey of a packet (1)131.215.44.214
Application 131.215.44.214 Send MSG to 128.125.253.146 5001
UDP UDP header MSG Send to 128.125.253.146
IP IP header UDP header MSG Send to 131.215.44.253 (from routing table) Send to 00906DE7D400 (from ARP)
MAC MAC header IP UDP MSG
Physic
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The Journey of a packet (1)131.215.44.214
Application 131.215.44.214 Send MSG to 128.125.253.146 5001
UDP UDP header MSG Send to 128.125.253.146
IP IP header UDP header MSG Send to 131.215.44.253 (from routing table) Send to 00906DE7D400 (from ARP)
MAC MAC header IP UDP MSG
Physic Send to the Ethernet
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The Journey of a packet (1)131.215.44.214-gt131.21
5.44.253
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The Journey of a packet (2)131.215.44.253
IP
MAC
Physic Get a packet From Ethernet Its for 00906DE7D400. Thats me. I should accept it.
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The Journey of a packet (2)131.215.44.253
IP
MAC OK, I am 00906DE7D400 Pass the packet to IP
Physic Get a packet from ethernet for 00906DE7D400
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The Journey of a packet (2)131.215.44.253
IP IP Header From 131.215.44.214 to 128.125.253.146 Should go to next router 131.215.254.254
MAC OK, I am 00906DE7D400 Pass the packet to IP
Physic Get a packet from ethernet for 00906DE7D400
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The Journey of a packet (2) 131.215.44.253
IP IP Header From 131.215.44.214 to 128.125.253.146 Should go to next router 131.215.254.254 Send to zzzzzzzzzzzz (from ARP)
MAC
Physic
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The Journey of a packet (2) 131.215.44.253
IP IP Header From 131.215.44.214 to 128.125.253.146 Should go to next router 131.215.254.254 Send to zzzzzzzzzzzz (from ARP)
MAC MAC header IP UDP MSG
Physic
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The Journey of a packet (2) 131.215.44.253
IP IP Header From 131.215.44.214 to 128.125.253.146 Should go to next router 131.215.254.254 Send to zzzzzzzzzzzz (from ARP)
MAC MAC header IP UDP MSG
Physic Send to zzzzzzzzzzzz
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The Journey of a packet (2)131.215.44.253-gt131.21
5.254.254
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The Journey of a packet (n) 128.125.254.1-gt128.12
5.253.146
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The Journey of a packet (n) 128.125.253.146
Application I want to receive something on port 5001
UDP Listening to the port 5001
IP
MAC
Physic
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The Journey of a packet (n) 128.125.253.146
Application
UDP Listening to the Port 5001
IP
MAC
Physic Get a packet from ethernet for yyyyyyyyyyyy
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The Journey of a packet (n) 128.125.253.146
Application
UDP Listening to the Port 5001
IP
MAC Yes, I am yyyyyyyyyyyy Pass the packet to IP
Physic Get a packet From ethernet for yyyyyyyyyyyy
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The Journey of a packet (n) 128.125.253.146
Application
UDP Listening to port 5001
IP From 131.215.44.214 to 128.125.253.1465001 Yes, I am 128.125.253.146. Is there any program listening to this port? Yes. One UDP is waiting. Pass it to UDP
MAC Yes, I am yyyyyyyyyyyy Pass the packet to IP
Physic Get a packet From ethernet for yyyyyyyyyyyy
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The Journey of a packet (n) 128.125.253.146
Application Receive message from 131.215.44.214
UDP Pass to Application
IP From 131.215.44.214 to 128.125.253.146 Yes, I am 128.125.253.146. Is there any program waiting for it? Yes. One application is waiting. Pass it to UDP
MAC Yes, I am yyyyyyyyyyyy Pass the packet to IP
Physic Get a packet From Ethernet For yyyyyyyyyyyy
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Overview
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Necessary Information (1)

• Where shall I pass the packet, for a given
  destination IP address? Routing Table
• Exmaple
• weixl_at_orchestragt route

Destination Gateway Gen-mask Flags Interface
131.215.44.0 255.255.255.0 U Eth0
127.0.0.0 255.0.0.0 U lo
default 131.215.44.254 0.0.0.0 UF Eth0
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Necessary Information (2)

• Where shall I pass the packet, for a given
  destination IP address? -- Arp
• Exmaple
• weixl_at_orchestragt arp -a
• 131.215.44.227 at 00065BDEC572 on eth0
• 131.215.44.142 at 0060B07CE802 on eth0
• 131.215.44.113 at 00A0C95A266D on eth0
• 131.215.44.80 at 00E081027F7B on eth0
• 131.215.44.254 at 00000C07AC01 on eth0
• 131.215.44.253 at 00906DE7D400 on eth0
• 131.215.44.12 at 0020781B132C on eth0
• 131.215.44.14 at 00A0C9062F2A on eth0

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More Information (Bonus)

• Get your phone book (Domain Name Service).
• Example
• weixl_at_orchestragt ping login.cs.caltech.edu
• PING orchestra.cs.caltech.edu (131.215.44.20)
  from 131.215.44.20 56(84) bytes of data.
• weixl_at_orchestragt freebsd-login.cs.caltech.edu
  (131.215.44.14)
• API
• gethostbyname()

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How does DNS work?

• www.mit.edu?
• 18.181.0.31

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Connection
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Streamless Connection
Application Socket_send/receive DNS
UDP UDP send/receive
IP Routing (IP / ARP)
MAC Ethernet or other LAN
Physic Electronic/Optical signals
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Stream Connection
Application Socket_send/receive DNS
TCP How to establish/maintain a connection?
IP Routing (IP / ARP)
MAC Ethernet/Token Ring or other direct links
Physic Electronic/Optical signals
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Stream Connection

• An Example At 1-626-395-3555 Call DMV
• Prerequisite
• You know the number of DMV (1-800-777-0133)
• The service is now open at DMV.
• There is a link between the two phones.

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Stream Connection

• An Example At 1-626-395-3555 Call DMV

• Steps at your site
• Establish the phone
• Dial the number
• Select the service
• Talk
• Hang up

• Steps at DMV
• Establish the phone
• Establish the service on phone
• Accept your request
• Talk
• Hang Up

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Stream Connection

• Steps at your site
• Establish the phone
• Dial the number
• Select the service
• Talk to the representative
• Hang up

• Steps at DMV
• Establish the phone
• Establish the service on phone
• Accept your request
• Talk to you
• Hang Up

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Stream Connection

• Steps at clients site
• Establish the socket
• Dial the number
• Select the service
• Talk to the representative
• Hang up

• Steps at your site
• Establish the phone
• Dial the number
• Select the service
• Talk to the representative
• Hang up

• Steps at servers site
• Establish the socket
• Establish the service
• Accept your request
• Talk to you
• Hang Up

• Steps at DMV
• Establish the phone
• Establish the service on phone
• Accept your request
• Talk to you
• Hang Up

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Stream Connection

• Steps at clients site
• Establish the socket
• Dial the number
• Select the service
• Talk to the representative
• Hang up

• Steps at clients site
• Establish the socket
• Dial the number
• Select the service
• Talk to the representative
• Hang up

• Steps at servers site
• Establish the socket
• Bind socket to port Listen
• Accept your request
• Talk to you
• Hang Up

• Steps at servers site
• Establish the socket
• Establish the service on phone
• Accept your request
• Talk to you
• Hang Up

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Stream Connection

• Steps at clients site
• Establish the socket
• Dial the number
• Select the service
• Talk to the representative
• Hang up

• Steps at clients site
• Establish the socket
• connect the address ( IP
• port )
• Talk to the representative
• Hang up

• Steps at servers site
• Establish the socket
• Bind socket to a port Listen
• Accept your request
• Talk to you
• Hang Up

• Steps at servers site
• Establish the socket
• Bind socket to a port Listen
• Accept your request
• Talk to you
• Hang Up

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Stream Connection

• Steps at clients site
• Establish the socket
• connect the address ( IP
• port )
• Talk
• Hang up

• Steps at clients site
• Establish the socket
• connect the address ( IP
• port )
• Talk to the representative
• Hang up

• Steps at servers site
• Establish the socket
• Bind socket to a port Listen
• Accept the request from client
• Talk to you
• Hang Up

• Steps at servers site
• Establish the socket
• Bind socket to a port Listen
• Accept your request
• Talk to you
• Hang Up

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Stream Connection

• Steps at clients site
• Establish the socket
• connect the address ( IP
• port )
• Send/Receive Data
• Hang up

• Steps at clients site
• Establish the socket
• connect the address ( IP
• port )
• Talk
• Hang up

• Steps at servers site
• Establish the socket
• Bind socket to a port Listen
• Accept the request from client
• Send/Receive Data
• Hang Up

• Steps at servers site
• Establish the socket
• Bind socket to a port Listen
• Accept the request from client
• Talk to you
• Hang Up

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Stream Connection

• Steps at clients site
• Establish the socket
• connect the address ( IP
• port )
• Send/Receive Data
• Hang up

• Steps at clients site
• Establish the socket
• connect the address ( IP
• port )
• Send/Receive Data
• Hang up

• Steps at servers site
• Establish the socket
• Bind socket to a port Listen
• Accept the request from client
• Send/Receive Data
• Hang Up

• Steps at servers site
• Establish the socket
• Bind socket to a port Listen
• Accept the request from client
• Send/Receive Data
• Hang Up

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• Insight (from LinuxForum)

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CS 145A Lab 1Connection

• Netlab.caltech.edu/course

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How to establish a connection?

• UDP

• Steps at clients site
• Establish the socket
• Send Data to the address ( IP
• port )
• Close the socket

• Steps at servers site
• Establish the socket
• Bind socket to a port
• Receive Data
• Close the socket

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How to establish a connection?

• TCP

• Steps at clients site
• Establish the socket
• connect the address ( IP
• port )
• Send/Receive Data
• Close the socket

• Steps at servers site
• Establish the socket
• Bind socket to a port Listen
• Accept the request from client and create a new
  socket for communication
• Send/Receive Data on the new socket
• Close the socket

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Tasks for Lab 1

• Be familiar with the basic commands that we
  talked about in class (see those examples in the
  lecture).
• Write a program (server) that can act as a
  Server
• Write a program (udp client) that can send UDP
  packets
• Write a program (tcp client) that can send TCP
  packets

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Server

• accept TCP connections in one port
• The server should talk with the clients. That
  is, the server return the same contents as the
  client sends to it. If the client does not send
  anything in 10 seconds, the server should
  actively disconnect the connection.
• The server is able to talk with 5 different
  clients at the same time. The server should not
  keep more than 5 clients at the same time.

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Server

• accept UDP packets in one port (may be different
  from the TCP)
• The server should talk to the clients.
• The input format
• Server ltport 1gt ltport2gt
• (port 1 is for TCP, port2 is for UDP)

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Tcp client

• send a message to the server, wait for several
  seconds, then disconnect.
• Input format
• tcpclient lthostgt ltportgt ltmessagegt lttimegt
• lttimegt is a number indicating the seconds the
  client should wait before disconnection.

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Udp client

• send a message to the server
• Input format
• udpclient lthostgt ltportgt ltmessagegt

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Tips

• For the unknown commands, use man/
  info/Richard Stevens book
• Testing you can use telnet to test the server,
  use the server to test the clients.
• How to implement the disconnection after
  10-sec?
• Child-process
• select

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Submission (due Oct 18th)

• Task 1 route.txt arp.txt ifconfig.txt
  traceroute.txt
• Task 2 server.c server.txt
• Task 3 udpclient.c udpclient.txt
• Task 4 tcpclient.c tcpclient.txt
• Mailto cs145ta_at_cs.caltech.edu
• (Do NOT send to cs145class_at_cs.caltech.edu )
• Documents
• How to use the program compile, run
• Your design, your testing, the problems you met
• Any other comments

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Grading

• Correctness (70)
• Documentation and comments (20)
• Program style (10)

TA Hours

• Tue 2000 2200 JRG 154 / 170
• Thu 2000 2200 JRG 154 / 170