Transcript CS 351- Fall 2005 - Rutgers University

CS 352- Spring 2007
TA: Tuan Phan
Email: [email protected]
732-445-6450 (ext 9644) :
Just leaving msg( prefer using Email)
Th 8:10 – 9:00 PM @ ARC 107
Office Hour: Th 7:00 – 8:00 PM @ Hill 367
Recitation:
Extra: Email to setup appointment on Monday afternoon.
Instructor’s Web Site: http://remus.rutgers.edu/cs352/F07/
TA’s Web Site: http://paul.rutgers.edu/~tphan/cs352/
Slides for recitation, Useful Links
1
Introduction
• Email
– Email Header:
[CS352]…
• Grading
– Midterms: 30 % (15% each)
– Project: 35% (part 1: 10%, part 2: 10% & part 3: 15%)
– Final: 35 %
• Homework
– We won’t grade , BUT, we highly suggest you doing
them
2
Important Dates
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Midterm 1: Oct 9th
Project 1: Oct 15th
Project 2: Nov 5th
Midterm2: Nov 13th
Project 3: Nov 26th
Final : Dec 11
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What will be in recitations
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Summary of lectures
Sample Questions
Projects
More technical stuff
4
Tools for CS352
• PuTTy : ssh client without GUI
• XManager: ssh client with GUI
• WinSCP: to upload files to CEREAL
clusters
• Ethereal: capturing packet program
• IDE: Eclipse, emacs, vi …
5
CEREAL cluster
• Link: http://cereal.rutgers.edu/
– Use Linux machines; DO NOT use Sun
machines (including cereal.rutgers.edu)
– Java programming:
• http://java.sun.com/docs/books/tutorial/
• ILab: Hill 248
– Use Rutgers ID
– Transfer students: use temporary ID
– Problem: meet Robert Toth @ CoRE 232
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Sample Question 1: OSI
LAYERING
• Fill in the boxes with the function (1-7) and protocol (A-G) belonging
to them.
Layer
Typical Functions
Example Protocol
Application
Presentation
Session
Transport
Network
DataLink
Physical
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Sample Question 1(cont.)
• Functions:
1 Provides reliable end-to-end communication.
2 Represent bytes as different voltages.
3 Implement communication between two applications of the same type.
5 Groups several user-level connections into a single entity.
6 Provides reliable transfer of information between two adjacent nodes.
7 Decides the route a packet will take across the network.
4 Transform between big and little endian representations.
• Protocols:
A Telnet
B Ethernet
C User Datagram Protocol
D Category-5 Twisted Pair
E Internet Protocol
F Point-to-Point Protocol
G Tranmission Control Protocol
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Internet Architecture
FTP
HTTP
RTP
TFTP
UDP
TCP
IP
Ethernet
CAT-5
802.11
Single-Mode
Fiber
…
PPP
RS-232
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Network programming in Java
TCP/IP stack
Host A
Host B
Application Protocol
Application
Layer
Transport Protocols (UDP and TCP)
Transport
Layer
IP
IP
Data
Application
Layer
Transport
Layer
TCP/UDP
header
Data
TCP/UDP
header
Data
IP
Network
Layer
Network
Layer
Network
Layer
Network
Layer
Host-toNet Layer
Host-toNet Layer
Host-toNet Layer
Host-toNet Layer
IP
header
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Sample Question2:
ENCAPSULATION
Fit the following headers in the correct order in the frame
provided. UDP, Ethernet, DNS and IP.
If the application wants to send a payload (data) of 400
bytes to the destination and the headers are of the sizes
given below, what will be the size of the entire frame as
presented to the IP layer at the destination?
UDP: 50bytes, Ethernet:40bytes, DNS:20 byes, IP:30bytes
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Why DNS?
• On Internet, each machine has an unique IP
address, e.g, 100.100.1.201.
• The IP addresses are used to communicate
between 2 machines.
• Human is familiar with names: www.google.com,
mail.yahoo.com .
• Need a mechanism to convert from name to IP
address: DNS(Domain Name Service)
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Sample Question 8: DNS
•
Consider the internet in the figure below, in which zones are indicated with a
dashed line. There is only one DNS server per zone and it happens to have
the same name as the highest node in each zone: yale.edu, cs.yale.edu,
rutgers.edu, cs.rutgers.edu and root-servers.net.
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The only servers supporting recursive querying are cs.yale.edu and
cs.rutgers.edu.
For each of the queries below, list in order all the DNS servers contacted by
the resolver (located in the OS of the machine running the query). Assume
there is no caching performed at any level of the hierarchy.
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Sample Question 8: DNS(cont.)
•
A. (4 points) A machine called lab1.bio.yale.edu exists in the biology
department at Yale, and a user on eden.rutgers.edu launches this query:
"nslookup lab1.bio.yale.edu’’ .
•
B. (4 points) At the prompt of paul.cs.rutgers.edu somebody launches this
query: "nslookup lab1.bio.yale.edu" .
•
C. (4 points) Later, lab1.bio.yale.edu is assigned a new IP (but keeps the
same name) and is physically moved in the science building onto a local
Ethernet with other machines such as electron.eng.yale.edu and
theorem.eng.yale.edu. At the prompt of eden.rutgers.edu you launch this
query: "nslookup lab1.bio.yale.edu".
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D. (4 points) In the science building, on lab1.bio.yale.edu, somebody
queries: "nslookup paul.cs.rutgers.edu".
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E. (4 points) Follow the same scenario as in part (B), but this time indicate,
in order, all the queries involved in the process. Use this notation to
represent a query: rutgers.edu -> rootservers.net to indicate that
rutgers.edu is generating/forwarding a query to rootservers.net.
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Homework
1. Try to do all sample questions again.
2. Set-up account on CEREAL cluster.
3. Type the code in text book, p. 151 &
p155 for the 3rd version)
(p. 164 & 168 for the 4th version)
1. Compile and run them in CEREAL
cluster
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Build your own network
• 3 CS students live together -> How about a small
network connecting to Internet??? What equipments do
they need to buy?? Is it very expensive ???
• System Admin of a small company want to build a
network that connect 20 machines in the company. The
office locates in 2 floors of a building. What equipments
does he need to buy?
• HUB, switch, router … how to distinguish them?
• How to “touch” the network theories in class??
– TCP/IP, DNS, HTTP
– Packet capturing !!!
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ETHERNET
• TOPOLOGY: Bus & Tree
• BUS TOPOLOGY
NIC
Coaxial Cable
T-Connector/Transceiver
Receive
Receive
Transfer !!
Send
Terminator
Host
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ETHERNET – Tree Topology
Backbone HUB
Crossover
cable
CAT 5UTP cable
forward
straight
through
HUB
SWITCH
T
send
A
cable
B
C
X
Y
Z
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Straight through cable & crossover cable
Figure 3: Wiring for straight thru and crossover cables
Fig1: Typical RJ45 Connector
Figure 2: 8 wires in RJ45 that is labeled from 1 to 8
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MAC address
• Network Interface Card (NIC)
– Each NIC has its own MAC address , it is
stored on the chip!!
• Length of MAC : 48 bites = 6 bytes
• For examples: 00:C1:71:01:AB:F0
– Prefix: Company ID: 3Com, Netgear …
– Postfix: Serial Number
• Command to show MAC: ifconfig, ipconfig
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Ethernet Frame Structure
MAC Dest.
address
MAC Source
address
Type
DATA ….
CRC
• Type(2 bytes) specifies the network layer protocol: IP or
Novel IPX or ARP or RARP…
• CRC: check sum
• Broadcast:
– MAC Broadcast Address = FF:FF:FF:FF:FF:FF
• Host A sends a msg to host B:
– MAC dest = MAC B, MAC src = MAC A
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HUB vs. SWITCH
Ethernet Frame
MAC A -> MAC C
SWITCH can learn the MACs of
all nodes
DATA
HUB
SWITCH
forward
send
A
send
B
C
B can CAPTURE the packet
from A to C !!!!
A
B
C
B CAN’T capture the packet
from A to C !!!!
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How to build your own network!
• NICs
• HUB or SWITCH !!!
• 2 machines can be connected by using crossover
cable!!!
• Assign IP address
Crossover cable
– Static
– Dynamic
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DNS Protocol
Example
remus
Scenario:
remus tries to
resolve an IP address for
venus.cs.yale.edu
using a recursive query
1
8
ns-lcsr
2
7
a.root-servers.net
3
6
yale.edu
4
5
cs.yale.edu
DNS Protocol
Another Example
remus
1
Some servers do not support
Recursive queries
Scenario:
remus tries to
resolve an IP address for
venus.cs.yale.edu
using an iterative query
3
5
2
ns-lcsr
a.root-servers.net
4
6
yale.edu
7
8
cs.yale.edu