Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

Networking_Refresher.ppt

1,017 views

Published on

  • Be the first to comment

  • Be the first to like this

Networking_Refresher.ppt

  1. 1. “Almost” everything you need to know about networking! Mahdi Nasereddin
  2. 2. Before we start  Information Security Development Conference 2006  David Rowan, Senior Vice President and Director of Enterprise Technology Risk Management, Sun Trust Banks, Inc. • “Policy is Corporate Law” – reviewed by 75 people • HR Enforcement of Security Policy • “No Assumption of Privacy” • 50% of security problems are internal!! • Passwords
  3. 3. Update on Information Security Development Conference 2006 (Cont.)  David Rowan, Senior Vice President and Director of Enterprise Technology Risk Management, Sun Trust Banks, Inc. • Risk choices: – Accept it – Mitigate it – Insurance – Avoid it • “Certifications will get you interviewed, Character and skill will get you hired Leadership will get you promoted” • Phishing sites (7 sites/day, 2 hrs/site to bring it down)
  4. 4. Update on Information Security Development Conference 2006 (Cont.)  Passwords  A lot of research in this area  Interesting site (Passfaces)
  5. 5. The Basics  Hub?  Switches?  Collision Domains?  Routers?  Broadcast Domains?
  6. 6. Networking Basics  Internetworking Models  The OSI model • IMPORTANT: Reference Model • “A Reference Model is a conceptual blueprint of how communications should take place” • Created by ISO (International Organization for Standardization) in the 1970s to allow computer systems made by different vendors to communicate with each other
  7. 7. Open Systems Interconnection (OSI) 7. Application • Provides user interface Within the end • Initiates services Stations • Transfer data into standard format 6. Presentation before transmission • Keeps data different applications’ data 5. Session separate • Control the data exchange • Error Correction 4. Transport End to end transmission • Reliable or unreliable delivery 3. Network • Logical addressing for data packets • Routing is performed in this layer • NIC software function 2. Data Link • How data in packaged • Error detection “Not Correction” • Moves bits between devices 1. Physical • Specifies voltages, cables, and cables
  8. 8. Advantages of using the OSI model  Allows multiple-vendor development through standardization  Prevents changes in one layer from affecting other layers
  9. 9. Data Encapsulation
  10. 10. TCP/IP “DoD Model”
  11. 11. Process/Application Layer Protocols  Telnet “Virtual terminal”  File Transfer Protocol “FTP”  Trivial File Transfer Protocol “TFTP”  Network File System “NFS”  Simple Mail Transfer Protocol “SMTP”  Line Printer Daemon “LPD”  X Windows  Simple Network Management Protocol “SNMP”  Domain Name Service “DNS”  Dynamic Host Configuration Protocol “DHCP”
  12. 12. The Transport Layer “Host to Host”  Layer 4 of the OSI model  It segments and reassemble data into a data stream  Examples of transport layer protocols:  TCP  UDP
  13. 13. Transport Layer Concepts  Flow Control  Data integrity is ensured by maintaining flow control  Flow control prevents the sender from overflowing the receiver.  Flow control is established using 1. Connection oriented communication 2. Windowing 3. Acknowledgements
  14. 14. Connection-Oriented Communication
  15. 15. Please stop!! My buffer is full!!
  16. 16. Windowing
  17. 17. Transport Layer Protocols  Transmission Control Protocol “TCP” ACK, SYN, RESET, PUSH, URG, and FIN “See Page 31”
  18. 18. Transport Layer Protocols  User Datagram Protocol “UDP”
  19. 19. TCP versus UDP TCP UDP Sequenced Not sequenced Reliable Not reliable Connection Oriented Connectionless Virtual circuit Low overhead Three-way handshake No acknowledgement Windowing flow control No flow control
  20. 20. 3 way handshake Active participant Passive participant (client) (server)
  21. 21. Port Numbers  Used by TCP and UDP to communicate with upper layers keep track if different conversations crossing the network simultaneously  Sender port number start at 1024
  22. 22. Port Numbers to remember Port Application 21 ftp 23 telnet 53 DNS 69 TFTP 110 POP3 80 HTTP
  23. 23. The Network Layer “Internet”  Layer 3 of the OSI model, which handles data routing and addressing.  The network layer keeps track of the network devices and determines the best way to move data.  It uses IP or IPX address
  24. 24. IP Addressing  IP address x.x.x.x  Net Mask
  25. 25. The Network Layer  Routing Table  Network Addresses  Interface  Metric  Packets used in the network layer  Data packets • Routed protocols (examples: IP and IPX)  Route updates • Routing protocols (examples: OSPF, and RIP)
  26. 26. Routing  IP Routing is the process of moving packets from one network to another network.  To be able to route packets a router needs to know “at least” the following:  Destination address  Neighborhood routers  Possible routes to all remote networks  Best route to each remote network  How to maintain and verify routing information
  27. 27. Routing
  28. 28. Static versus Dynamic Routing  Static routing: The administrator has to enter the routing table MANUALLY!  Dynamic routing: routers update each others routing tables automatically
  29. 29. More About Routing  Routers by default will not forward any broadcast or multicast packets  Routers use the logical address in the network layer header to determine where to send the packet  Routers can use access lists
  30. 30. Internet Layer Protocols  Internet Protocol “IP”  Internet Control Message Protocol “ICMP”  Address Resolution Protocol “ARP”  Reverse Address Resolution Protocol “RARP”  DHCP “Dynamic Host Configuration Protocol”
  31. 31. Internet Protocol
  32. 32. Protocol Numbers Protocol Protocol Number ICMP 1 IGRP 9 IPv6 41 GRE 47 TCP 6 UDP 17
  33. 33. ARP  A machine has an IP but does not know the MAC Address  A table is maintained for IP to MAC translation  A translation is removed after 15 minutes if no update  Broadcast is used
  34. 34. DHCP  Automatically assigns IP addresses
  35. 35. ICMP  Error reporting  Examples  Host unreachable  ICMP-Redirect
  36. 36. The Data Link Layer “Network Access”  Layer 2 of the OSI model that is responsible for data transfer across a single physical connection (or series of bridged connections, between two Network entities).  It also handles error notification.  It uses the hardware address
  37. 37. Data Link Layers  The data link layer has 2 sublayers 1. Media Access Control (MAC) 802.3: – Defines how packets are placed on the media. – Physical addressing is defined here. 2. Logical Link Control (LLC) 802.2: – This layer is responsible for identifying the network protocols, and then encapsulating them  Switches are at the Data link layer. Why?
  38. 38. The Physical Layer “Network Access”  Layer 1 of the OSI model which concerns the mechanical, electrical and functional aspects of connections in a communications medium.  Hubs are at the Physical layer.
  39. 39. NAT and PAT?  Network Address Translation  Port Address Translation

×