networking kevin, ray, kelvin, stephan, norman, phil
TRANSCRIPT
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Networking
Kevin, Ray, Kelvin, Stephan, Norman, Phil
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History- ARPANET (Advanced Research Projects Agency
Network)- World's first operational packet-switching
network- Became the core network of what composes
the global Internet- Originally consisted of terminals in UCLA,
Standford, UCSB, and the University of Utah
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History
- DoD was concerned about our ability to survive a nuclear strike due to lack of a reliable communications network
- Paul Baran and Rand corp. say that most reliable would be a computer network which broke the message into units (packets) and sent them along to the destination
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Networks As We Know Them Today
• A collection of computers and devices interconnected by communications channels that facilitate communications among users and allows user to share resources
• Source: http://en.wikipedia.org/wiki/Computer_network
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Purposes of a Modern Network
• Facilitates communications– E-mail, IM’s, chat rooms
• Sharing hardware– A set of printers to be used by a whole office
• Sharing data• Sharing software– Running programs via a remote connection
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Outline
• Kevin – Network• Ray – IP'S and Packets• Kelvin – Sockets• Stephan – Security • Norman – Hardware• Phil - Conclusion
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IP addressesAnd
Packets
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IP’S And Macs
• NIC has unique Mac address(physical address)
• IP address is logical
• IPv4 and IPv6
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Packets
• All info on networks travel in packets
• Data is broken up and sent
• Each packet can take a different path
• Allows for best path
• Put back together when received
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EXAMPLE
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Packet structure
• Fixed length and varying length
• Three main partso Header(most important)
o Data
o Trailer
• Have error checking
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Header
• Contains all information about data being sent– Packet length
– Packet number
– Destination and origin
• Every packet contains header
• Can vary in size
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Other parts
• Data section contains the data
• Trailer identifies end
• Check sum error checking– All words in the message are XOR
– Receiving end performs same operation and includes original XOR
– If not all zeros error occurred
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Sockets
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What are sockets?
- Used for client/server interaction
- Mechanism for transfer of data
- Socket API is provided by the OS
- Interface between applications and networking and transfer protocols
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How do sockets work?
- Server process waits for client
- Server accepts and binds client
- Server waits for client request
- Server replies to request
- Close
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How do sockets work? (Diagram)
Link:
http://publib.boulder.ibm.com/infocenter/iseries/v5r4/topic/rzab6/rxab6500.gif
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Accepting connections
- Usually threaded to listen on many ports
- Client sends a connection request
- Server binds the client using IP and port number- Analogous to telephone/ext
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Transferring Data
- Sockets are identified by socket identifier, aka socket number
- OS decodes packets to determine socket number, then forwards payload to application
- Sockets are bidirectional
- Different kinds of sockets use different protocols (TCP/UDP/etc.)
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Security
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What is it? Protection Layers of security Administrator privileges
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How does it work Authentication of user Firewall enforced policies What about worms and viruses? Need IPS or IDS Encryption
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IPS and IDS Intrusion Detection System(IDS)
Network Intrusion Detection System Host-based Intrusion Detection System NIDS HIDS
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IPS and IDS cont... Intrusion Prevention System(IPS) Improvement of IDS Classifications
NIPS – Network-based Intrusion Prevention WIPS – Wireless-based Intrusion Prevention NBA – Network Behavior Analysis HIPS – Host-based Intrusion Prevention
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Detection Methods Signature-based Detection Statistical Anomaly-Based Detection Stateful Protocol Analysis Detection
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Hardware
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Network Interface Card
• Simply an I/O device• Sends and receives data to the network in the
form of packets• Will do DMA reads/writes directly to/from
main memory• Can generate headers, but this is usually done
by the CPU
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Network Interface Card
• After creating the frame or packet, the OS will create a buffer descriptor which will tell where and how large the data is
• After creating the buffer descriptor, the OS will notify the NIC that it is ready
• The NIC will then do a DMA read for the descriptor and then for the actual frame
• The frame is then sent out to the network
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Network Interface Card
• OS will also have the NIC keep buffer descriptors pointing to free space in main memory
• When a frame is received, it will do a DMA write to main memory
• It will then modify the descriptor to reflect the received data, DMA write it to memory, and notify the OS that a frame is ready
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Drivers
• Handles the translation from standard I/O function calls to the hardware’s specific required software in order to run
• Can run in both kernel and user mode• Kernel mode used mainly for speed• User mode used mainly for stability
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Hub
• Sends all packets to all other systems connected to it
• High tendency to cause data collisions– Collisions refer to when two or more systems send
data over the network, requiring the now-fragmented data to be retransmitted
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Switch
• Like a hub, connects multiple systems together to form a new network
• Operates by forwarding data to specific systems on the network
• May be able to be piggy-backed, but may also require crossover cables
• Have unmanaged and managed modes where unmanaged refers to plug-and-play
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Switch
• Avoids data collisions by sending data only to its intended destination as a full-duplex machine
• Keeps track of MAC addresses of each connected system (nodes) in a table
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Router
• Connects networks together and forwards traffic between them
• Most have built-in switches• Performs the job of a computer which acts as
a gateway (much cheaper than the computer)
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Router
ComputerInternet Switch
Computer
Computer
Computer
RouterInternet Switch
Computer
Computer
Computer
Internet Modern Router
Computer
Computer
Computer
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Conclusion
What did we learn?