2019 FRSecure CISSP Mentor Program: Class Six
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This document summarizes a CISSP mentor program session from April 29, 2019. It discusses completing chapters 1-4 of the curriculum, switching to questions from other sources, and covering network architecture and design topics like network defense in depth, fundamental network concepts of simplex/half-duplex/full-duplex communication, baseband/broadband, analog/digital, LANs/WANs/MANs/GANs/PANs, and circuit-switched vs. packet-switched networks. The session included quizzes and 134 slides to go over these topics.
![The TCP/IP Model - Application Layer
• aka the Process Layer:
• Emphasis is on maximum flexibility for software developers.
• Handles all high level protocols:
• FTP, HTTP, SMTP [ TCP examples ]
• TFTP, SNMP, DHCP, DNS, BOOTP [ UDP examples ]
• Data representation, encoding and dialog control.
• Ensures data is properly packaged for the next layer.
CISSP® MENTOR PROGRAM – SESSION SIX
56
LECTURE
Fundamental Network Concepts](https://image.slidesharecdn.com/frsecurecisspmentorprogram-2019classsix-190429134107/85/2019-FRSecure-CISSP-Mentor-Program-Class-Six-57-320.jpg)
![The TCP/IP Model - Application Layer
• aka the Process Layer:
• Emphasis is on maximum flexibility for software developers.
• Handles all high level protocols:
• FTP, HTTP, SMTP [ TCP examples ]
• TFTP, SNMP, DHCP, DNS, BOOTP [ UDP examples ]
• Data representation, encoding and dialog control.
• Ensures data is properly packaged for the next layer.
CISSP® MENTOR PROGRAM – SESSION SIX
57
LECTURE
Fundamental Network Concepts](https://image.slidesharecdn.com/frsecurecisspmentorprogram-2019classsix-190429134107/85/2019-FRSecure-CISSP-Mentor-Program-Class-Six-58-320.jpg)
2019 FRSecure CISSP Mentor Program: Class Six
- 1. 2019 CISSP MENTOR PROGRAM April 29, 2019 ----------- Class 6 – April 29, 2019 Instructors: • Brad Nigh, FRSecure Director of Professional Services & Innovation • Evan Francen, FRSecure & SecurityStudio CEO
- 2. Great job so far! Keep it up, you can do this! • We’ve completed chapters 1 – 4 so far. • Arguably, the hardest part is behind us! • Check-in. • How many have read Chapter 1 - 4? • Questions? CISSP® MENTOR PROGRAM – SESSION SIX 1 WE’RE ALL BACK! Let’s get on it! OK, maybe 160 slides was a little ambitious. We’re not going as fast tonight, but we’re still going fast. 134 slides tonight!
- 3. Great job so far! Keep it up, you can do this! • We’ve completed chapters 1 – 4 so far. • Arguably, the hardest part is behind us! • Check-in. • How many have read Chapter 1 - 4? • Questions? CISSP® MENTOR PROGRAM – SESSION SIX 2 WE’RE ALL BACK! Let’s get on it! OK, maybe 160 slides was a little ambitious. We’re not going as fast tonight, but we’re still going fast. 134 slides tonight! Other Updates: REMINDER: We’ve got a Slack channel set up for all students. • Did you get the invite?! • If not, email cisspmentor@frsecure.com and we’ll get you one ASAP. • Get some Q&A and activity going up in there!
- 4. 1. What type of sprinkler system would be best for an art gallery? A. Wet pipe B. Dry pipe C. Deluge D. Pre-action CISSP® MENTOR PROGRAM – SESSION SIX 3 QUIZ… Easy peezy – We’ll be switching up questions from other sources soon.
- 5. 1. What type of sprinkler system would be best for an art gallery? A. Wet pipe B. Dry pipe C. Deluge D. Pre-action CISSP® MENTOR PROGRAM – SESSION SIX 4 QUIZ… Easy peezy – We’ll be switching up questions from other sources soon.
- 6. 2. What is the primary drawback in using dogs as a perimeter control? A. Training B. Cost C. Liability D. Appearance CISSP® MENTOR PROGRAM – SESSION SIX 5 QUIZ… Easy peezy – We’ll be switching up questions from other sources soon.
- 7. 2. What is the primary drawback in using dogs as a perimeter control? A. Training B. Cost C. Liability D. Appearance CISSP® MENTOR PROGRAM – SESSION SIX 6 QUIZ… Easy peezy – We’ll be switching up questions from other sources soon.
- 8. 3. The RSA algorithm is based on which one-way function? A. Elliptic curves B. Discrete logarithm C. Frequency distribution D. Factoring composite numbers into their primes CISSP® MENTOR PROGRAM – SESSION SIX 7 QUIZ… Easy peezy – We’ll be switching up questions from other sources soon.
- 9. 3. The RSA algorithm is based on which one-way function? A. Elliptic curves B. Discrete logarithm C. Frequency distribution D. Factoring composite numbers into their primes CISSP® MENTOR PROGRAM – SESSION SIX 8 QUIZ… Easy peezy – We’ll be switching up questions from other sources soon.
- 10. 4. You are surfing the web via a wireless network. Your wireless connection becomes unreliable, so you plug into a wired network to continue surfing. While you changed physical networks, your browser required no change. What security feature allows this? A. Abstraction B. Hardware Segmentation C. Layering D. Process Isolation CISSP® MENTOR PROGRAM – SESSION SIX 9 QUIZ… Easy peezy – We’ll be switching up questions from other sources soon.
- 11. 4. You are surfing the web via a wireless network. Your wireless connection becomes unreliable, so you plug into a wired network to continue surfing. While you changed physical networks, your browser required no change. What security feature allows this? A. Abstraction B. Hardware Segmentation C. Layering D. Process Isolation CISSP® MENTOR PROGRAM – SESSION SIX 10 QUIZ… Easy peezy – We’ll be switching up questions from other sources soon.
- 12. 5. A criminal deduces that an organization is holding an off-site meeting and has few people in the building, based on the low traffic volume to and from the parking lot, and uses the opportunity to break into the building to steal laptops. What type of attack has been launched? A. Aggregation B. Emanations C. Inference D. Maintenance Hook CISSP® MENTOR PROGRAM – SESSION SIX 11 QUIZ… Easy peezy – We’ll be switching up questions from other sources soon.
- 13. 5. A criminal deduces that an organization is holding an off-site meeting and has few people in the building, based on the low traffic volume to and from the parking lot, and uses the opportunity to break into the building to steal laptops. What type of attack has been launched? A. Aggregation B. Emanations C. Inference D. Maintenance Hook CISSP® MENTOR PROGRAM – SESSION SIX 12 QUIZ… Easy peezy – We’ll be switching up questions from other sources soon.
- 14. 6. What is the most important goal of fire suppression systems? A. Preservation of critical data B. Safety of personnel C. Building integrity D. Quickly extinguishing a fire CISSP® MENTOR PROGRAM – SESSION SIX 13 QUIZ… Easy peezy – We’ll be switching up questions from other sources soon.
- 15. 6. What is the most important goal of fire suppression systems? A. Preservation of critical data B. Safety of personnel C. Building integrity D. Quickly extinguishing a fire CISSP® MENTOR PROGRAM – SESSION SIX 14 QUIZ… Easy peezy – We’ll be switching up questions from other sources soon.
- 16. CISSP® MENTOR PROGRAM – SESSION SIX 15 LET’S DO THIS! Picking up where we left off.
- 17. • Network Architecture and Design • Secure Network Devices and Protocols • Secure Communications CISSP® MENTOR PROGRAM – SESSION SIX 16 WHAT ARE WE GOING TO COVER? Agenda – Domain 4: Communication and Network Security Starting on page 219 this evening Great domain for the techies. A little more challenging for the “normal” people…
- 18. Network Defense-in-Depth • Assume that an attacker has already compromised your perimeter. • Network segmentation, isolation, etc. • NSA Methodology for Adversary Obstruction (not testable, but great guidance) - https://www.cdse.edu/documents/cdse/nsa- methodology-for-adversary-obstruction.pdf CISSP® MENTOR PROGRAM – SESSION SIX 17 LECTURE Network Architecture and Design
- 19. Network Defense-in-Depth • Assume that an attacker has already compromised your perimeter. • Network segmentation, isolation, etc. • NSA Methodology for Adversary Obstruction (not testable, but great guidance) - https://www.cdse.edu/documents/cdse/nsa- methodology-for-adversary-obstruction.pdf CISSP® MENTOR PROGRAM – SESSION SIX 18 LECTURE Network Architecture and Design
- 20. Network Defense-in-Depth • Assume that an attacker has already compromised your perimeter. • Network segmentation, isolation, etc. • NSA Methodology for Adversary Obstruction (not testable, but great guidance) - https://www.cdse.edu/documents/cdse/nsa- methodology-for-adversary-obstruction.pdf CISSP® MENTOR PROGRAM – SESSION SIX 19 LECTURE Network Architecture and Design
- 21. Simplex, Half-Duplex, and Full-Duplex Communication • Simplex communication is one-way, like a car radio tuned to a music station. • Half-duplex communication sends or receives at one time only (not simultaneously), like a walkie talkie. • Full-duplex communications sends and receive simultaneously, like two people having a face-to-face conversation. CISSP® MENTOR PROGRAM – SESSION SIX 20 LECTURE Fundamental Network Concepts
- 22. Baseband and Broadband • Baseband networks have one channel, and can only send one signal at a time • Ethernet networks are baseband • “100baseT” UTP cable means 100 megabit, baseband, and twisted pair • Broadband networks have multiple channels and can send multiple signals at a time, like cable TV CISSP® MENTOR PROGRAM – SESSION SIX 21 LECTURE Fundamental Network Concepts
- 23. Analog & Digital • Analog communications are a continuous wave of information • Digital communications transfer data in bits: ones and zeroes CISSP® MENTOR PROGRAM – SESSION SIX 22 LECTURE Fundamental Network Concepts
- 24. LANs, WANs, MANs, GANs, and PANs • PANs are Personal Area Networks • Typically a range of 100 meters or much less • Low-power wireless technologies such as Bluetooth use PANs. • LAN is a Local Area Network • A comparatively small network • Typically confined to a building or an area within one • MAN is a Metropolitan Area Network • Typically confined to a city, a zip code, a campus, or office park • WAN is a Wide Area Network • Typically covering cities, states, or countries • GAN is a Global Area Network; a global collection of WANs. CISSP® MENTOR PROGRAM – SESSION SIX 23 LECTURE Fundamental Network Concepts
- 25. Circuit-Switched Networks • A dedicated circuit or channel (portion of a circuit) is dedicated between two nodes • Can provide dedicated bandwidth to point-to-point connections • Original voice networks were circuit-switched • One drawback of circuit-switched networks: once a channel or circuit is connected, it is dedicated to that purpose, even while no data is being transferred CISSP® MENTOR PROGRAM – SESSION SIX 24 LECTURE Fundamental Network Concepts
- 26. Packet-Switched Networks • Instead of using dedicated circuits, data is broken into packets, each sent individually • If multiple routes are available between two points on a network, packet switching can choose the best route, and fall back to secondary routes in case of failure • Packets may take any path (and different paths) across a network, and are then reassembled by the receiving node • Missing packets can be retransmitted, and out of-order packets can be re-sequenced. • Unlike circuit-switched networks, packet-switched networks make unused bandwidth available for other connections CISSP® MENTOR PROGRAM – SESSION SIX 25 LECTURE Fundamental Network Concepts
- 27. Packet-Switched Networks • Instead of using dedicated circuits, data is broken into packets, each sent individually • If multiple routes are available between two points on a network, packet switching can choose the best route, and fall back to secondary routes in case of failure • Packets may take any path (and different paths) across a network, and are then reassembled by the receiving node • Missing packets can be retransmitted, and out of-order packets can be re-sequenced. • Unlike circuit-switched networks, packet-switched networks make unused bandwidth available for other connections CISSP® MENTOR PROGRAM – SESSION SIX 26 LECTURE Fundamental Network Concepts
- 28. Layered Design • Models such as OSI and TCP/IP • Each layer performs a specific function • The complexity of each layer’s functionality is contained within its layer • Changes in one layer do not directly affect another: changing your physical network connection from wired to wireless (at Layer 1) has no effect on your Web browser (at Layer 7) CISSP® MENTOR PROGRAM – SESSION SIX 27 LECTURE Fundamental Network Concepts
- 29. Models and Stacks • A network model is a description of how a network protocol suite operates • A network stack is a network protocol suite programmed in software or hardware • Protocol - set of rules that end points in a telecommunication connection use when they communicate. Protocols specify interactions between the communicating entities. CISSP® MENTOR PROGRAM – SESSION SIX 28 LECTURE Fundamental Network Concepts
- 30. The OSI Model • OSI (Open System Interconnection) Reference Model is a layered network model • The model is abstract: we do not directly run the OSI model in our systems • Used as a reference point, so “Layer 1” (physical) is universally understood • Has seven layers • Developed by International Organization for Standardization (ISO) • Formally called “X.200: Information technology—Open Systems Interconnection—Basic Reference Model.” - downloaded for free at: http://www.itu.int/rec/T-REC-X.200-199407-I/en CISSP® MENTOR PROGRAM – SESSION SIX 29 LECTURE Fundamental Network Concepts
- 31. The OSI Model • OSI (Open System Interconnection) Reference Model is a layered network model • The model is abstract: we do not directly run the OSI model in our systems • Used as a reference point, so “Layer 1” (physical) is universally understood • Has seven layers • Developed by International Organization for Standardization (ISO) • Formally called “X.200: Information technology—Open Systems Interconnection—Basic Reference Model.” - downloaded for free at: http://www.itu.int/rec/T-REC-X.200-199407-I/en CISSP® MENTOR PROGRAM – SESSION SIX 30 LECTURE Fundamental Network Concepts
- 32. The OSI Model • OSI (Open System Interconnection) Reference Model is a layered network model • The model is abstract: we do not directly run the OSI model in our systems • Used as a reference point, so “Layer 1” (physical) is universally understood • Has seven layers • Developed by International Organization for Standardization (ISO) • Formally called “X.200: Information technology—Open Systems Interconnection—Basic Reference Model.” - downloaded for free at: http://www.itu.int/rec/T-REC-X.200-199407-I/en CISSP® MENTOR PROGRAM – SESSION SIX 31 LECTURE Fundamental Network Concepts
- 33. The OSI Model - Layer 1: Physical • Describes units of data such as bits represented by energy (such as light, electricity, or radio waves) and the medium used to carry them (such as copper or fiber optic cables) • Cabling standards such as Thinnet, Thicknet, and Unshielded Twisted Pair (UTP) exist at layer 1, among many others • Layer 1 devices include hubs and repeaters CISSP® MENTOR PROGRAM – SESSION SIX 32 LECTURE Fundamental Network Concepts
- 34. The OSI Model - Layer 1: Physical • Describes units of data such as bits represented by energy (such as light, electricity, or radio waves) and the medium used to carry them (such as copper or fiber optic cables) • Cabling standards such as Thinnet, Thicknet, and Unshielded Twisted Pair (UTP) exist at layer 1, among many others • Layer 1 devices include hubs and repeaters CISSP® MENTOR PROGRAM – SESSION SIX 33 LECTURE Fundamental Network Concepts
- 35. The OSI Model - Layer 2: Data link • Handles access to the physical layer as well as local area network communication • An Ethernet card and its MAC (Media Access Control) address are at Layer 2, as are switches and bridges. • Divided into two sub-layers: • Media Access Control (MAC) - transfers data to and from the physical layer - touches Layer 1 • Logical Link Control (LLC) -handles LAN communications - touches Layer 3 CISSP® MENTOR PROGRAM – SESSION SIX 34 LECTURE Fundamental Network Concepts
- 36. The OSI Model - Layer 2: Data link • Handles access to the physical layer as well as local area network communication • An Ethernet card and its MAC (Media Access Control) address are at Layer 2, as are switches and bridges. • Divided into two sub-layers: • Media Access Control (MAC) - transfers data to and from the physical layer - touches Layer 1 • Logical Link Control (LLC) -handles LAN communications - touches Layer 3 CISSP® MENTOR PROGRAM – SESSION SIX 35 LECTURE Fundamental Network Concepts
- 37. The OSI Model - Layer 3: Network • Describes routing: moving data from a system on one LAN to a system on another • IP addresses and routers • Protocols include IPv4 and IPv6, among others. CISSP® MENTOR PROGRAM – SESSION SIX 36 LECTURE Fundamental Network Concepts
- 38. The OSI Model - Layer 3: Network • Describes routing: moving data from a system on one LAN to a system on another • IP addresses and routers • Protocols include IPv4 and IPv6, among others. CISSP® MENTOR PROGRAM – SESSION SIX 37 LECTURE Fundamental Network Concepts
- 39. The OSI Model - Layer 4: Transport • Handles packet sequencing, flow control, and error detection • TCP and UDP are Layer 4 protocols • Resending or re-sequencing packets CISSP® MENTOR PROGRAM – SESSION SIX 38 LECTURE Fundamental Network Concepts
- 40. The OSI Model - Layer 4: Transport • Handles packet sequencing, flow control, and error detection • TCP and UDP are Layer 4 protocols • Resending or re-sequencing packets CISSP® MENTOR PROGRAM – SESSION SIX 39 LECTURE Fundamental Network Concepts
- 41. The OSI Model - Layer 5: Session • Manages sessions, providing maintenance on connections • Remote Procedure Calls (RPCs) • A good way to remember the session layer’s function is “connections between applications” • Simplex, half-duplex, and full-duplex communication. CISSP® MENTOR PROGRAM – SESSION SIX 40 LECTURE Fundamental Network Concepts
- 42. The OSI Model - Layer 5: Session • Manages sessions, providing maintenance on connections • Remote Procedure Calls (RPCs) • A good way to remember the session layer’s function is “connections between applications” • Simplex, half-duplex, and full-duplex communication. CISSP® MENTOR PROGRAM – SESSION SIX 41 LECTURE Fundamental Network Concepts
- 43. The OSI Model - Layer 6: Presentation • Presents data to the application (and user) in a comprehensible way • Concepts include data conversion, characters sets such as ASCII, and image formats such as GIF (Graphics Interchange Format), JPEG (Joint Photographic Experts Group), and TIFF (Tagged Image File Format) CISSP® MENTOR PROGRAM – SESSION SIX 42 LECTURE Fundamental Network Concepts
- 44. The OSI Model - Layer 6: Presentation • Presents data to the application (and user) in a comprehensible way • Concepts include data conversion, characters sets such as ASCII, and image formats such as GIF (Graphics Interchange Format), JPEG (Joint Photographic Experts Group), and TIFF (Tagged Image File Format) CISSP® MENTOR PROGRAM – SESSION SIX 43 LECTURE Fundamental Network Concepts
- 45. The OSI Model - Layer 7: Application • Where you interface with your computer application • Web browser, word processor, and instant messaging clients exist at Layer 7 • Protocols Telnet and FTP CISSP® MENTOR PROGRAM – SESSION SIX 44 LECTURE Fundamental Network Concepts
- 46. The OSI Model - Layer 7: Application • Where you interface with your computer application • Web browser, word processor, and instant messaging clients exist at Layer 7 • Protocols Telnet and FTP CISSP® MENTOR PROGRAM – SESSION SIX 45 LECTURE Fundamental Network Concepts
- 47. The OSI Model Many mnemonics exist to help remember the OSI model: • “Please Do Not Throw Sausage Pizza Away” (Physical Data-Link Network Transport Session Presentation Application) • “Please Do Not Tell Sales People Anything.” • “All People Seem to Need Data Processing” CISSP® MENTOR PROGRAM – SESSION SIX 46 LECTURE Fundamental Network Concepts
- 48. The OSI Model Many mnemonics exist to help remember the OSI model: • “Please Do Not Throw Sausage Pizza Away” (Physical Data-Link Network Transport Session Presentation Application) • “Please Do Not Tell Sales People Anything.” • “All People Seem to Need Data Processing” CISSP® MENTOR PROGRAM – SESSION SIX 47 LECTURE Fundamental Network Concepts
- 49. The TCP/IP Model • TCP/IP model (Transmission Control Protocol/Internet Protocol) • Popular network model created by the United States Defense Advanced Research Projects Agency in the 1970s (see: http://www.isoc.org/internet/history/brief.shtml for more information) • A suite of protocols including UDP (User Datagram Protocol) and ICMP (Internet Control Message Protocol), among many others • Some sources use Link Layer in place of Network Access Layer, and Network layer in place of Internet Layer CISSP® MENTOR PROGRAM – SESSION SIX 48 LECTURE Fundamental Network Concepts
- 50. The TCP/IP Model • TCP/IP model (Transmission Control Protocol/Internet Protocol) • Popular network model created by the United States Defense Advanced Research Projects Agency in the 1970s (see: http://www.isoc.org/internet/history/brief.shtml for more information) • A suite of protocols including UDP (User Datagram Protocol) and ICMP (Internet Control Message Protocol), among many others • Some sources use Link Layer in place of Network Access Layer, and Network layer in place of Internet Layer CISSP® MENTOR PROGRAM – SESSION SIX 49 LECTURE Fundamental Network Concepts
- 51. The TCP/IP Model - Network Access Layer • Combines layers 1 (Physical) and 2 (Data Link) of the OSI model • Describes Layer 1 issues such as energy, bits, and the medium used to carry them (copper, fiber, wireless, etc.) • Also describes Layer 2 issues such as converting bits into protocol units such as Ethernet frames, MAC (Media Access Control) addresses, and Network Interface Cards (NICs) • Networks include: • WAN - Wide Area Network • LAN - Local Area Network • Internet CISSP® MENTOR PROGRAM – SESSION SIX 50 LECTURE Fundamental Network Concepts
- 52. The TCP/IP Model - Internet Layer • Aligns with the Layer 3 (Network) layer of the OSI model • IP addresses and routing • IPv4, IPv6, ICMP, and routing protocols (among others) • IP (Internet Protocol) governs the Internet layer. (All packets go through IP!) • Best path determination and packet switching occur at this layer CISSP® MENTOR PROGRAM – SESSION SIX 51 LECTURE Fundamental Network Concepts
- 53. The TCP/IP Model - Host-to-host Transport Layer • Sometimes called either “Host-to-Host” or, more commonly, “Transport” alone • Connects the Internet Layer to the Application Layer • Where applications are addressed on a network, via ports • TCP and UDP are the two Transport Layer protocols CISSP® MENTOR PROGRAM – SESSION SIX 52 LECTURE Fundamental Network Concepts
- 54. The TCP/IP Model - Host-to-host Transport Layer TCP - Transmission Control Protocol: • Connection-oriented protocol. • supports dialogues between source and destination. • packages application information into segments. • provides reliable full-duplex transmission. • supports flow control that exchanges packets. • windowing, acknowledgements. • retransmission - resends anything not received. CISSP® MENTOR PROGRAM – SESSION SIX 53 LECTURE Fundamental Network Concepts
- 55. The TCP/IP Model - Host-to-host Transport Layer UDP - User Datagram Protocol: • Connectionless protocol that exchanges datagrams. • does not provide flow control. • does not support windowing, acknowledgments or guaranteed delivery. • error processing and retransmission must be handled by other protocols. • unreliable. CISSP® MENTOR PROGRAM – SESSION SIX 54 LECTURE Fundamental Network Concepts
- 56. The TCP/IP Model - Application Layer • Combines Layers 5 though 7 (Session, Presentation, and Application) of the OSI mode • Most of these protocols use a client-server architecture, where a client (such as ssh) connects to a listening server (called a daemon on UNIX systems) such as sshd • Clients and servers use either TCP or UDP (and sometimes both) as a Transport Layer protocol • Protocols include SSH, Telnet and FTP, among many others CISSP® MENTOR PROGRAM – SESSION SIX 55 LECTURE Fundamental Network Concepts
- 57. The TCP/IP Model - Application Layer • aka the Process Layer: • Emphasis is on maximum flexibility for software developers. • Handles all high level protocols: • FTP, HTTP, SMTP [ TCP examples ] • TFTP, SNMP, DHCP, DNS, BOOTP [ UDP examples ] • Data representation, encoding and dialog control. • Ensures data is properly packaged for the next layer. CISSP® MENTOR PROGRAM – SESSION SIX 56 LECTURE Fundamental Network Concepts
- 58. The TCP/IP Model - Application Layer • aka the Process Layer: • Emphasis is on maximum flexibility for software developers. • Handles all high level protocols: • FTP, HTTP, SMTP [ TCP examples ] • TFTP, SNMP, DHCP, DNS, BOOTP [ UDP examples ] • Data representation, encoding and dialog control. • Ensures data is properly packaged for the next layer. CISSP® MENTOR PROGRAM – SESSION SIX 57 LECTURE Fundamental Network Concepts
- 59. Encapsulation • Takes information from a higher layer and adds a header to it, treating the higher layer information as data • “One layer’s header is another layer’s data.” • As the data moves down the stack in the TCP/IP model, application layer data is encapsulated in a layer 4 TCP segment. That TCP segment is encapsulated in a Layer 3 IP packet. That IP packet is encapsulated in a Layer 2 Ethernet frame. The frame is then converted into bits at Layer 1 and sent across the local network. • Data, segments, packets, frames, and bits are examples of Protocol Data Units (PDUs) • Reverse of encapsulation is called de-multiplexing (sometimes called de-encapsulation) CISSP® MENTOR PROGRAM – SESSION SIX 58 LECTURE Fundamental Network Concepts
- 60. Encapsulation • Takes information from a higher layer and adds a header to it, treating the higher layer information as data • “One layer’s header is another layer’s data.” • As the data moves down the stack in the TCP/IP model, application layer data is encapsulated in a layer 4 TCP segment. That TCP segment is encapsulated in a Layer 3 IP packet. That IP packet is encapsulated in a Layer 2 Ethernet frame. The frame is then converted into bits at Layer 1 and sent across the local network. • Data, segments, packets, frames, and bits are examples of Protocol Data Units (PDUs) • Reverse of encapsulation is called de-multiplexing (sometimes called de-encapsulation) CISSP® MENTOR PROGRAM – SESSION SIX 59 LECTURE Fundamental Network Concepts
- 61. Encapsulation • Takes information from a higher layer and adds a header to it, treating the higher layer information as data • “One layer’s header is another layer’s data.” • As the data moves down the stack in the TCP/IP model, application layer data is encapsulated in a layer 4 TCP segment. That TCP segment is encapsulated in a Layer 3 IP packet. That IP packet is encapsulated in a Layer 2 Ethernet frame. The frame is then converted into bits at Layer 1 and sent across the local network. • Data, segments, packets, frames, and bits are examples of Protocol Data Units (PDUs) • Reverse of encapsulation is called de-multiplexing (sometimes called de-encapsulation) CISSP® MENTOR PROGRAM – SESSION SIX 60 LECTURE Fundamental Network Concepts
- 62. Network Access, Internet and Transport Layer Protocols and Concepts • TCP/IP is a protocol suite: including (but not limited to): • IPv4 and IPv6 at Layer 3 • TCP and UDP at Layer 4 • A multitude of protocols at layers 5-7, including Telnet, FTP, SSH, and many others • Some protocols, such as IP, fit neatly into one layer (Internet). Others, such as Address Resolution Protocol (ARP), help connect one layer to another (Network Access to Internet in ARP’s case) CISSP® MENTOR PROGRAM – SESSION SIX 61 LECTURE Network Architecture and Design
- 63. MAC Addresses • Unique hardware address of an Ethernet network interface card (NIC) • Typically “burned in” at the factory • MAC addresses may be changed in software • Burned-in MAC addresses should be unique • Historically, MAC addresses were 48 bits long: • Two halves: the first 24 bits form the Organizationally Unique Identifier (OUI) • Last 24 bits form a serial number (formally called an extension identifier) • Organizations that manufacture NICs, such as Cisco, Juniper, HP, IBM, and many others, purchase 24-bit OUIs from the Institute of Electrical and Electronics Engineers (IEEE), Incorporated Registration Authority. A List of registered OUIs is available at http://standards.ieee.org/regauth/oui/oui.txt CISSP® MENTOR PROGRAM – SESSION SIX 62 LECTURE Network Architecture and Design
- 64. MAC Addresses • Unique hardware address of an Ethernet network interface card (NIC) • Typically “burned in” at the factory • MAC addresses may be changed in software • Burned-in MAC addresses should be unique • Historically, MAC addresses were 48 bits long: • Two halves: the first 24 bits form the Organizationally Unique Identifier (OUI) • Last 24 bits form a serial number (formally called an extension identifier) • Organizations that manufacture NICs, such as Cisco, Juniper, HP, IBM, and many others, purchase 24-bit OUIs from the Institute of Electrical and Electronics Engineers (IEEE), Incorporated Registration Authority. A List of registered OUIs is available at http://standards.ieee.org/regauth/oui/oui.txt CISSP® MENTOR PROGRAM – SESSION SIX 63 LECTURE Network Architecture and Design
- 65. EUI-64 MAC addresses • IEEE created the EUI-64 (Extended Unique Identifier) standard for 64-bit MAC addresses • OUI is still 24 bits, but the serial number is 40 bits • Allows far more MAC addresses, compared with 48-bit addresses CISSP® MENTOR PROGRAM – SESSION SIX 64 LECTURE Network Architecture and Design
- 66. IPv4 • Internet Protocol version 4, commonly called “IP” • Fundamental protocol of the Internet • Designed in the 1970s to support packet-switched networking • Used for the ARPAnet, which later became the Internet • IP is a simple protocol, designed to carry data across networks CISSP® MENTOR PROGRAM – SESSION SIX 65 LECTURE Network Architecture and Design
- 67. IPv4 • Requires a “helper protocol” called ICMP • IP is connectionless and unreliable: it provides “best effort” delivery of packets • If connections or reliability are required, they must be provided by a higher level protocol carried by IP, such as TCP • Uses 32-bit source and destination addresses, usually shown in “dotted quad” format, such as “192.168.2.4” • 32-bit address field allows 232, or nearly 4.3 billion addresses • Lack of IPv4 addresses is a fundamental problem: one of the factors leading to the creation of IPv6, which uses 128-bit addresses CISSP® MENTOR PROGRAM – SESSION SIX 66 LECTURE Network Architecture and Design
- 68. IPv4 - Key IPv4 Header Fields • An IP header is 20 bytes long (with no options) • Key fields are: • Version: IP version (4 for IPv4) • IHL: Length of the IP header • Type of Service: sets the precedence of the packet • Identification, Flags, Offset: used for IP fragmentation • Time To Live: to end routing loops • Protocol: embedded protocol (TCP, UDP, etc.) • Source and Destination IP addresses • (Optional) Options and padding CISSP® MENTOR PROGRAM – SESSION SIX 67 LECTURE Network Architecture and Design
- 69. IPv4 - Key IPv4 Header Fields • An IP header is 20 bytes long (with no options) • Key fields are: • Version: IP version (4 for IPv4) • IHL: Length of the IP header • Type of Service: sets the precedence of the packet • Identification, Flags, Offset: used for IP fragmentation • Time To Live: to end routing loops • Protocol: embedded protocol (TCP, UDP, etc.) • Source and Destination IP addresses • (Optional) Options and padding CISSP® MENTOR PROGRAM – SESSION SIX 68 LECTURE Network Architecture and Design
- 70. IPv4 - IP Fragmentation • If a packet exceeds the Maximum Transmission Unit (MTU) of a network • May be fragmented by a router along the path • MTU is the maximum PDU size on a network • Fragmentation breaks a large packet into multiple smaller packets • Typical MTU size for an IP packet is 1500 bytes • IP Identification field (IPID) is used to re-associate fragmented packets (they will have the same IPID) • Flags are used to determine if fragmentation is allowed, and whether more fragments are coming • Fragment offset gives the data offset the current fragment carries: “Copy this data beginning at offset 1480” • Path MTU discovery uses fragmentation to discover the largest size packet allowed across a network path • If a large packet is sent with the DF (do not fragment) flag sent and a router with a smaller MTU than the packet size will drop it, sending a “Fragmentation needed and DF set” ICMP message CISSP® MENTOR PROGRAM – SESSION SIX 69 LECTURE Network Architecture and Design
- 71. IPv6 • Successor to IPv4 • Larger address space (128 bit addresses compared to IPv4’s 32 bits) • Simpler routing • Simpler address assignment • Lack of IPv4 addresses was the primary factor that led to the creation of IPv6 CISSP® MENTOR PROGRAM – SESSION SIX 70 LECTURE Network Architecture and Design Note - IPv6 address space is 2128; there are over 340 undecillion (called 340 sextillion) total addresses, which is a 39-digit number in decimal: 340,282,366, 920,938,463,463,374,607,431,768,211,456.
- 72. IPv6 • The IPv6 header is larger and simpler than IPv4 • Fields include: • Version: IP version (6 for IPv6) • Traffic Class and Flow Label: used for QoS (Quality of Service) • Payload Length: length of IPv6 data (not including the IPv6 header) • Next header: next embedded protocol header • Hop Limit: to end routing loops CISSP® MENTOR PROGRAM – SESSION SIX 71 LECTURE Network Architecture and Design
- 73. IPv6 • The IPv6 header is larger and simpler than IPv4 • Fields include: • Version: IP version (6 for IPv6) • Traffic Class and Flow Label: used for QoS (Quality of Service) • Payload Length: length of IPv6 data (not including the IPv6 header) • Next header: next embedded protocol header • Hop Limit: to end routing loops CISSP® MENTOR PROGRAM – SESSION SIX 72 LECTURE Network Architecture and Design
- 74. IPv6 Addresses and Autoconfiguration • IPv6 hosts can statelessly autoconfigure a unique address, omitting the need for static addressing or DHCP • Stateless autoconfiguration takes the host’s MAC address and uses it to configure the IPv6 address • IPv6 addresses are 128 bits long, and use colons instead of periods to delineate section • One series of zeroes may be condensed into two colons (“::”). • Stateless autoconfiguration removes the requirement for DHCP (Dynamic Host Configuration Protocol) • DHCP may be used with IPv6: this called “stateful autoconfiguration” CISSP® MENTOR PROGRAM – SESSION SIX 73 LECTURE Network Architecture and Design
- 75. IPv6 Addresses and Autoconfiguration • The “ifconfig” (left) shows two IPv6 addresses: • fc01::20c:29ff:feef:1136/64 (Scope:Global) • fe80::20c:29ff:feef:1136/64 (Scope:Link) • The first address (fc01::…) is a “global” (routable) address, used for communication beyond the local network • IPv6 hosts rely on IPv6 routing advertisements to assign the global address • The second address (fe80::…) is a link-local address, used for local network communication only • Systems assign link-local addresses independently, without the need for an IPv6 router advertisement • /64 is the network size in CIDR format; means the network prefix is 64 bits long: the full global prefix is fc01:0000:0000:0000 CISSP® MENTOR PROGRAM – SESSION SIX 74 LECTURE Network Architecture and Design
- 76. IPv6 Addresses and Autoconfiguration • The host uses the following process to statelessly configure its global address: • Take the MAC address: 00:0c:29:ef:11:36 • Embed the “ffee” constant in the middle two bytes: 00:0c:29:ff:fe:ef:11:36 • Set the “Universal Bit”: 02:0c:29:ff:fe:ef:11:36 • Prepend the network prefix & convert to “:” format: fc01:0000:0000:0000:020c:29ff:feef:1136 • Convert one string of repeating zeroes to “::”: fc01::20c:29ff:feef:1136 CISSP® MENTOR PROGRAM – SESSION SIX 75 LECTURE Network Architecture and Design Note: systems may be “dual stack” and use both IPv4 and IPv6 simultaneously
- 77. IPv6 Security Challenges • An IPv6-enabled system will automatically configure a link-local address (beginning with fe80:…) without the need for any other ipv6-enabled infrastructure. The host can communicate with other link-local addresses on the same LAN. This is true even if the administrators are unaware that IPv6 is now flowing on their network. • ISPs are also enabling IPv6 service, sometimes without the customer’s knowledge. Modern network tools, such as networked intrusion detection systems, can “see” IPv6, but are often not configured to do so. • Many network professionals have limited experience or understanding of IPv6. From an attacker’s perspective, this can offer a golden opportunity to launch attacks or exfiltrate data via IPv6. • All network services that are not required should be disabled: this is a fundamental part of system hardening. If IPv6 is not required, it should be disabled CISSP® MENTOR PROGRAM – SESSION SIX 76 LECTURE Network Architecture and Design
- 78. Classful Networks (back to IPv4) • Original IPv4 networks (before 1993) were “classful” • Classified in classes A through E • Class A through C were used for normal network use. Class D was multicast, and Class E was reserved CISSP® MENTOR PROGRAM – SESSION SIX 77 LECTURE Network Architecture and Design
- 79. Classless Inter-Domain Routing • CIDR allows for many network sizes beyond the arbitrary stateful network sizes. • The Class A network 10.0.0.0 contains IP address that begins with 10: i.e. 10.3.96.223. In other words, 10.X.X.X is a Class A address. The first 8 bits of the dotted-quad IPv4 address is the network (10); the remaining 24 bits are the host address: 3.96.223 in the last pervious example • CIDR notation for a Class A network is /8 for this reason: 10.0.0.0/8. The “/8” is the netmask, which means the network portion is 8 bits long, leaving 24 bits for the host • The class C network of 192.0.2.0 contains any IP address that begins with 192.0.2: 192.0.2.177, 192.0.2.253, etc. That class C network is 192.0.2.0/24 in CIDR format: the first 24 bits (192.0.2) describe the network; the remaining 8 bits (177 or 253 in the previous example) describe the host • Once networks are described in CIDR notation, additional routable network sizes are possible • If you only need 128 IP addresses, chop a Class C (/24) in half, resulting in two /25 networks • If you only need 64 IP addresses, chop a /24 network into quarters, resulting in four /26 networks with 64 IP addressed each CISSP® MENTOR PROGRAM – SESSION SIX 78 LECTURE Network Architecture and Design
- 80. RFC 1918 Addressing • RFC 1918 addresses are private IPv4 addresses • Used for internal traffic that does not route via the Internet • Allows conservation of IPv4 addresses • Three blocks of IPv4 addresses are set aside for RFC 1918: • 10.0.0.0-10.255.255.255 (10.0.0.0/8) • 172.16.0.0-172.31.255.255 (172.16.0.0/12) • 192.168.0.0-192.168.255.255 (192.168.0.0/16) • Any public Internet connection using un-translated RFC1918 addresses as a destination will fail • Internet traffic sent with an un-translated RFC 1918 source address will never return • RFC stands for “Request for Comments,” a way to discuss and publish standards on the Internet • More information about RFC 1918 is available at: http://www.rfc- editor.org/rfc/rfc1918.txt CISSP® MENTOR PROGRAM – SESSION SIX 79 LECTURE Network Architecture and Design Note - Memorizing RFC numbers is not generally required for the exam; RFC 1918 addresses are an exception to that rule.
- 81. Network Address Translation • Used to translate IP addresses • Frequently used to translate RFC1918 addresses as they pass from intranets to the Internet • Three types of NAT are: • Static NAT • Makes a one-to-one translation between addresses, such as 192.168.1.47→192.0.2.252 • Pool NAT (also known as dynamic NAT) • Reserves a number of public IP addresses in a pool • Addresses can be assigned from the pool, and then returned. • Port Address Translation (PAT, also known as NAT overloading) • Typically makes a many-to-one translation from multiple private addresses to one public IP address • Common solution for homes and small offices: multiple internal devices such as laptops, desktops and mobile devices share one public IP address CISSP® MENTOR PROGRAM – SESSION SIX 80 LECTURE Network Architecture and Design
- 82. ARP and RARP ARP is the Address Resolution Protocol • Used to translate between Layer 2 MAC addresses and Layer 3 IP addresses • Resolves IPs to MAC addresses by asking “Who has IP address 192.168.2.140, tell me,” for example. An example of an ARP reply is “192.168.2.140 is at 00:0c:29:69:19:66.” • 10.23.51.960019 arp who-has 192.168.2.140 tell 192.168.2.4 • 10.23.51.960019 arp reply 192.168.2.140 is-at 00:0c:29:69:19:66 • Any local system could answer the ARP request, including an attacker. Secure networks should consider hard-coding ARP entries for this reason. CISSP® MENTOR PROGRAM – SESSION SIX 81 LECTURE Network Architecture and Design
- 83. ARP and RARP • RARP is used by diskless workstations to request an IP address • A node asks “Who has MAC address at 00:40:96:29:06:51, tell 00:40:96:29:06:51 • 05:30:01.495795 ARP, Reverse Request who-is 00:40:96:29:06:51 tell 00:40:96:29:06:51 • A RARP server answers with the node’s IP address. CISSP® MENTOR PROGRAM – SESSION SIX 82 LECTURE Network Architecture and Design
- 84. Unicast, Multicast, and Broadcast Traffic • Unicast – one-to-one communication • Multicast – one-to-many communication • Broadcast – one-to-all communication CISSP® MENTOR PROGRAM – SESSION SIX 83 LECTURE Network Architecture and Design
- 85. Limited and Directed Broadcast Addresses • Broadcast traffic is sent to all stations on a LAN • There are two types of IPv4 broadcast addresses: • Limited broadcast • Limited broadcast address is 255.255.255.255 • “limited” because it is never forwarded across a router • Directed broadcast • Also called net-directed • Broadcast address of the 192.0.2.0/24 network is 192.0.2.255 (the host portion of the address is all “1”s in binary, or 255) • Called “directed” broadcast, because traffic to these addresses may be sent from remote networks (it may be “directed”). CISSP® MENTOR PROGRAM – SESSION SIX 84 LECTURE Network Architecture and Design
- 86. Layer 2 Broadcast • Reaches all nodes in a “broadcast domain” • A switch is an example of a broadcast domain • The Ethernet broadcast address is MAC address “FF:FF:FF:FF:FF:FF” • Traffic on an Ethernet switch is received by all connected nodes CISSP® MENTOR PROGRAM – SESSION SIX 85 LECTURE Network Architecture and Design
- 87. Promiscuous Network Access • Accesses all unicast traffic on a network segment • Systems such as Networked Intrusion Detection Systems (NIDS) require promiscuous network access in order to monitor all traffic on a network • Network nodes normally only “see” unicast traffic sent directly to them • Accessing unicast traffic sent to other nodes requires two things: • A network interface card (NIC) configured in promiscuous mode • The ability to access other unicast traffic on a network segment. • Devices such as switches provide traffic isolation, so that each host will only receive unicast traffic sent to it (in addition to broadcast and multicast traffic) • A hub, switch SPAN port, or TAP is typically used to provide promiscuous network access. CISSP® MENTOR PROGRAM – SESSION SIX 86 LECTURE Network Architecture and Design
- 88. TCP • Reliable Layer 4 protocol • Uses a three-way handshake to create reliable connections across a network • Can reorder segments that arrive out of order, and retransmit missing segments CISSP® MENTOR PROGRAM – SESSION SIX 87 LECTURE Network Architecture and Design
- 89. Key TCP Header Fields • A TCP header is 20 bytes long (with no options) • Important fields include: • Source and Destination port • Sequence and Acknowledgement Numbers: Keep full-duplex communication in sync • TCP Flags • Window Size: Amount of data that may be sent before receiving acknowledgement CISSP® MENTOR PROGRAM – SESSION SIX 88 LECTURE Network Architecture and Design
- 90. Key TCP Header Fields • A TCP header is 20 bytes long (with no options) • Important fields include: • Source and Destination port • Sequence and Acknowledgement Numbers: Keep full-duplex communication in sync • TCP Flags • Window Size: Amount of data that may be sent before receiving acknowledgement CISSP® MENTOR PROGRAM – SESSION SIX 89 LECTURE Network Architecture and Design
- 91. TCP Ports • TCP connects from a source port to a destination port, such as from source port 51178 to destination port 22 • The TCP port field is 16 bits, allowing port numbers from 0 to 65535 • There are two types of ports: • Reserved - 1023 or lower • Ephemeral - 1024-65535 • Common services such as HTTP use well-known ports • The Internet Assigned Numbers Authority (IANA) maintains a list of well-known ports at http://www.iana.org/assignments/port- numbers • Most Linux and UNIX systems have a smaller list of well-known ports in /etc/services CISSP® MENTOR PROGRAM – SESSION SIX 90 LECTURE Network Architecture and Design
- 92. Socket Pairs • A socket is a combination of an IP address and a TCP or UDP port on one node • A socket may “listen” (wait for a connection) • A socket pair is then “established” during a connection • A socket pair describes a unique connection between two nodes: • Source port • Source IP • Destination port • Destination IP • Netstat output: CISSP® MENTOR PROGRAM – SESSION SIX 91 LECTURE Network Architecture and Design
- 93. TCP Flags • The original six TCP flags are: • URG: Packet contains urgent data • ACK: Acknowledge received data • PSH: Push data to application layer • RST: Reset (tear down) a connection • SYN: Synchronize a connection • FIN: Finish a connection (gracefully) • Two new TCP flags were added in 2001: • CWR (Congestion Window Reduced) • ECE (Explicit Congestion Notification Echo) CISSP® MENTOR PROGRAM – SESSION SIX 92 LECTURE Network Architecture and Design
- 94. The TCP handshake • TCP uses a three-way handshake to establish a reliable connection • The connection is full duplex, and both sides synchronize (SYN) and acknowledge (ACK) each other • Exchange of these four flags is performed in three steps: SYN, SYN- ACK, ACK • The client chooses an initial sequence number, set in the first SYN packet • The server also chooses its own initial sequence number, set in the SYN/ACK packet • Each side acknowledges each other’s sequence number by incrementing it: this is the acknowledgement number • Once a connection is established, ACKs typically follow for each segment • The connection will eventually end with a RST (reset or tear down the connection) or FIN (gracefully end the connection) CISSP® MENTOR PROGRAM – SESSION SIX 93 LECTURE Network Architecture and Design
- 95. The TCP handshake • TCP uses a three-way handshake to establish a reliable connection • The connection is full duplex, and both sides synchronize (SYN) and acknowledge (ACK) each other • Exchange of these four flags is performed in three steps: SYN, SYN- ACK, ACK • The client chooses an initial sequence number, set in the first SYN packet • The server also chooses its own initial sequence number, set in the SYN/ACK packet • Each side acknowledges each other’s sequence number by incrementing it: this is the acknowledgement number • Once a connection is established, ACKs typically follow for each segment • The connection will eventually end with a RST (reset or tear down the connection) or FIN (gracefully end the connection) CISSP® MENTOR PROGRAM – SESSION SIX 94 LECTURE Network Architecture and Design
- 96. UDP • User Datagram Protocol • A simpler and faster cousin to TCP • No handshake, session, or reliability • Informally called “Send and Pray” • Has a simpler and shorter 8-byte header • Fields include: • Source IP • Destination IP • Packet length (header and data) • Simple (and optional) checksum - if used, the checksum provides limited integrity to the UDP header and data • Operates at Layer 4 • Commonly used for applications that are “lossy” (can handle some packet loss), such as streaming audio and video • Also used for query-response applications, such as DNS queries. CISSP® MENTOR PROGRAM – SESSION SIX 95 LECTURE Network Architecture and Design
- 97. ICMP • Internet Control Message Protocol • Helper protocol that helps Layer 3 (IP) • ICMP is used to troubleshoot and report error conditions • No concept of ports, but instead uses types and codes • Commonly-used ICMP types are echo request and echo reply (used for ping) and time to live exceeded in transit (used for traceroute) CISSP® MENTOR PROGRAM – SESSION SIX 96 LECTURE Network Architecture and Design
- 98. ICMP • Internet Control Message Protocol • Helper protocol that helps Layer 3 (IP) • ICMP is used to troubleshoot and report error conditions • No concept of ports, but instead uses types and codes • Commonly-used ICMP types are echo request and echo reply (used for ping) and time to live exceeded in transit (used for traceroute) CISSP® MENTOR PROGRAM – SESSION SIX 97 LECTURE Network Architecture and Design
- 99. ICMP - Ping • Named after sonar used to “ping” submarines • Sends an ICMP Echo Request to a node and listens for an ICMP Echo Reply • Designed to determine whether a node is up or down • Attackers use ICMP to map target networks; many sites filter types of ICMP such as Echo Request and Echo Reply • An unanswered ping (an ICMP Echo Request with no Echo Reply) does not mean a host is down. The node may be down, or the node may be up and the Echo Request or Echo Reply may have been filtered at some point. CISSP® MENTOR PROGRAM – SESSION SIX 98 LECTURE Network Architecture and Design
- 100. ICMP - Traceroute • Uses ICMP Time Exceeded messages to trace a network route • The Time to Live field is used to avoid routing loops: every time a packet passes through a router, the router decrements the TTL field. If the TTL reaches zero, the router drops the packet and sends an ICMP Time Exceeded message to the original sender • Client’s traceroute client sends a packet to the server with a TTL of 1. The router A decrements the TTL to 0, drops the packet, and sends an ICMP Time Exceeded message to the client. Router A is now identified. • The client then sends a packet with a TTL of 2 to the server. Router A decrements the TTL to 1 and passes the packet to router B. Router B decrements the TTL to 0, drops it, and sends an ICMP Time Exceeded message to the client. Router B is now identified. • This process continues until the server is reached • Most traceroute clients (such as UNIX and Cisco) send UDP packets outbound CISSP® MENTOR PROGRAM – SESSION SIX 99 LECTURE Network Architecture and Design
- 101. ICMP - Traceroute • Uses ICMP Time Exceeded messages to trace a network route • The Time to Live field is used to avoid routing loops: every time a packet passes through a router, the router decrements the TTL field. If the TTL reaches zero, the router drops the packet and sends an ICMP Time Exceeded message to the original sender • Client’s traceroute client sends a packet to the server with a TTL of 1. The router A decrements the TTL to 0, drops the packet, and sends an ICMP Time Exceeded message to the client. Router A is now identified. • The client then sends a packet with a TTL of 2 to the server. Router A decrements the TTL to 1 and passes the packet to router B. Router B decrements the TTL to 0, drops it, and sends an ICMP Time Exceeded message to the client. Router B is now identified. • This process continues until the server is reached • Most traceroute clients (such as UNIX and Cisco) send UDP packets outbound CISSP® MENTOR PROGRAM – SESSION SIX 100 LECTURE Network Architecture and Design
- 102. Application Layer TCP/IP Protocols and Concepts • TCP/IP’s Application Layer - combines the Presentation, Session, and Application Layers of the OSI model • Only standardizes communication and depends upon the underlying transport layer protocols to establish host-to-host data transfer channels and manage the data exchange CISSP® MENTOR PROGRAM – SESSION SIX 101 LECTURE Network Architecture and Design
- 103. Telnet • Provides terminal emulation over a network • “Terminal” means text-based VT100-style terminal access • Telnet servers listen on TCP port 23 • Weak because it provides no confidentiality: all data transmitted during a telnet session is plaintext, including the username and password used to authenticate to the system • Also has limited integrity: attackers with write access to a network can alter data, or even seize control of Telnet sessions • Secure Shell (SSH) provides secure authentication, confidentiality, and integrity and is a recommended replacement for Telnet. CISSP® MENTOR PROGRAM – SESSION SIX 102 LECTURE Network Architecture and Design
- 104. FTP • Used to transfer files to and from servers • FTP has no confidentiality or integrity and should not be used to transfer sensitive data over insecure channels • FTP uses two ports: • The control connection (where commands are sent) is TCP port 21 • “Active FTP” uses a data connection (where data is transferred) which originates from TCP port 20 • The two socket pairs (the next two examples use arbitrary ephemeral ports): • Client:1025→Server:21 (Control Connection) • Server:20→Client: 1026 (Data Connection) • Client:1025→Server:21 (Control Connection) • Client 1026→Server:1025 (Data Connection) • The data connection originates from the server, in the opposite direction of the control channel. Many firewalls will block the active FTP data connection for this reason, breaking Active FTP. Passive FTP addresses this issue by keeping all communication from client to server: • The FTP server tells the client which listening data connection port to connect to; the client then makes a second connection. Passive FTP is more likely to pass through firewalls cleanly, since it flows in classic client-server direction. CISSP® MENTOR PROGRAM – SESSION SIX 103 LECTURE Network Architecture and Design
- 105. TFTP • Trivial File Transfer Protocol • UDP port 69 • Simple way to transfer files; often used for saving router configurations or “bootstrapping” (downloading an operating system) via a network by diskless workstations • No authentication or directory structure: files are read from and written to one directory, usually called /tftpboot. • No confidentiality or integrity CISSP® MENTOR PROGRAM – SESSION SIX 104 LECTURE Network Architecture and Design
- 106. SSH • Designed as a secure replacement for Telnet, FTP, and the UNIX “R” commands (rlogin, rshell, etc) • Provides confidentiality, integrity, and secure authentication, among other features • Includes SFTP (SSH FTP) and SCP (Secure Copy) for transferring files • Can also be used to securely tunnel other protocols, such as HTTP • SSH servers listen on TCP port 22 by default • SSH version 1 was the original version, which has since been found vulnerable to man-in-the middle attacks • SSH version 2 is the current version of the protocol, and is recommended over SSHv1, or Telnet, FTP, etc. CISSP® MENTOR PROGRAM – SESSION SIX 105 LECTURE Network Architecture and Design
- 107. SMTP, POP, and IMAP • SMTP is the Simple Mail Transfer Protocol • Used to transfer email between servers • Servers listen on TCP port 25 • POPv3 (Post Office Protocol) and IMAP (Internet Message Access Protocol) are used for client-server email access, which use TCP ports 110 and 143, respectively CISSP® MENTOR PROGRAM – SESSION SIX 106 LECTURE Network Architecture and Design
- 108. DNS • Domain Name System • A distributed global hierarchical database that translates names to IP addresses, and vice versa • Uses both TCP and UDP: small answers use UDP port 53; large answers (such as zone transfers) use TCP port 53 • Authoritative name servers provide the “authoritative” resolution for names within a given domain • Recursive name servers will attempt to resolve names that it does not already know • Caching name servers will temporarily cache names previously resolved CISSP® MENTOR PROGRAM – SESSION SIX 107 LECTURE Network Architecture and Design
- 109. DNS • Domain Name System • A distributed global hierarchical database that translates names to IP addresses, and vice versa • Uses both TCP and UDP: small answers use UDP port 53; large answers (such as zone transfers) use TCP port 53 • Authoritative name servers provide the “authoritative” resolution for names within a given domain • Recursive name servers will attempt to resolve names that it does not already know • Caching name servers will temporarily cache names previously resolved CISSP® MENTOR PROGRAM – SESSION SIX 108 LECTURE Network Architecture and Design
- 110. DNS Weaknesses • DNS uses the unreliable UDP protocol for most requests, and native DNS provides no authentication. The security of DNS relies on a 16-bit source port and 16-bit DNS query ID. Attackers who are able to blindly guess both numbers can forge UDP DNS responses. • A DNS cache poisoning attack is an attempt to trick a caching DNS server into caching a forged response. If bank.example.com is at 192.0.2.193, and evil.example.com is at 198.18.8.17, an attacker may try to poison a DNS server’s cache by sending the forged response of “bank.example.com is at 198.18.8.17.” If the caching DNS name server accepts the bogus response, it will respond with the poisoned response for subsequent bank.example.com requests (until the record expires). CISSP® MENTOR PROGRAM – SESSION SIX 109 LECTURE Network Architecture and Design
- 111. DNSSEC • Domain Name Server Security Extensions provides authentication and integrity to DNS responses via the use of public key encryption • DNSSEC does not provide confidentiality: it acts like a digital signature for DNS responses • See http://www.kb.cert.org/vuls/id/800113 for more details on the improved cache poisoning attack and defenses CISSP® MENTOR PROGRAM – SESSION SIX 110 LECTURE Network Architecture and Design
- 112. DNSSEC • Domain Name Server Security Extensions provides authentication and integrity to DNS responses via the use of public key encryption • DNSSEC does not provide confidentiality: it acts like a digital signature for DNS responses • See http://www.kb.cert.org/vuls/id/800113 for more details on the improved cache poisoning attack and defenses CISSP® MENTOR PROGRAM – SESSION SIX 111 LECTURE Network Architecture and Design
- 113. HTTP and HTTPS • HTTP (Hypertext Transfer Protocol) - Used to transfer unencrypted Web-based data • HTTPS (Hypertext Transfer Protocol Secure) - transfers encrypted Web-based data via SSL/TLS • HTTP uses TCP port 80 • HTTPS uses TCP port 443 CISSP® MENTOR PROGRAM – SESSION SIX 112 LECTURE Network Architecture and Design
- 114. BOOTP and DHCP • BOOTP is the Bootstrap Protocol • Used for bootstrapping via a network by diskless systems • Many system BIOSs now support BOOTP directly, allowing the BIOS to load the operating system via a network without a disk • Startup occurs in two phases: • Use BOOTP to determine the IP address and OS image name • Use TFTP to download the operating system • DHCP is Dynamic Host Configuration Protocol • Designed to replace and improve on BOOTP by adding additional features • Allows more configuration options, as well as assigning temporary IP address leases to systems • Systems can be configured to receive IP address leases, DNS servers, and default gateways, among other information. • Both BOOTP and DHCP use the same ports: • UDP port 67 for servers • UDP port 68 for clients CISSP® MENTOR PROGRAM – SESSION SIX 113 LECTURE Network Architecture and Design
- 115. Layer 1 Network Cabling • Simplest part of the OSI model • Fundamental network cabling terms to understand: • Electro Magnetic Interference (EMI) is interference caused by magnetism created by electricity • Any unwanted signal (such as EMI) on a network cable is called noise • Crosstalk occurs when a signal crosses from one cable to another • Attenuation is the weakening of signal as it travels further from the source CISSP® MENTOR PROGRAM – SESSION SIX 114 LECTURE Network Architecture and Design
- 116. Layer 1 Network Cabling - Twisted Pair Cabling Unshielded Twisted Pair (UTP) • Uses pairs of wire twisted together • Twisting them together dampens the magnetism and makes cabling less susceptible to EMI CISSP® MENTOR PROGRAM – SESSION SIX 115 LECTURE Network Architecture and Design
- 117. Layer 1 Network Cabling - Twisted Pair Cabling Unshielded Twisted Pair (UTP) • Cables are classified by categories according to rated speed • Tighter twisting results in more dampening: • Category 6 UTP cable designed for gigabit networking has far tighter twisting than a Category 3 fast Ethernet cable • Cisco Press also has a good summary at http://www.ciscopress.com/articles/article.asp?p=31276 CISSP® MENTOR PROGRAM – SESSION SIX 116 LECTURE Network Architecture and Design
- 118. Layer 1 Network Cabling - Twisted Pair Cabling Unshielded Twisted Pair (UTP) • Cables are classified by categories according to rated speed • Tighter twisting results in more dampening: • Category 6 UTP cable designed for gigabit networking has far tighter twisting than a Category 3 fast Ethernet cable • Cisco Press also has a good summary at http://www.ciscopress.com/articles/article.asp?p=31276 CISSP® MENTOR PROGRAM – SESSION SIX 117 LECTURE Network Architecture and Design
- 119. Layer 1 Network Cabling - Twisted Pair Cabling Unshielded Twisted Pair (UTP) • Cables are classified by categories according to rated speed • Tighter twisting results in more dampening: • Category 6 UTP cable designed for gigabit networking has far tighter twisting than a Category 3 fast Ethernet cable • Cisco Press also has a good summary at http://www.ciscopress.com/articles/article.asp?p=31276 CISSP® MENTOR PROGRAM – SESSION SIX 118 LECTURE Network Architecture and Design
- 120. Layer 1 Network Cabling - Coaxial Cabling • Coaxial cables are often used for satellite and cable TV service • More resistant to EMI, allows higher bandwidth and longer connections compared with twisted pair cable. • Two older types of coaxial cable are Thinnet and Thicknet, used for Ethernet bus networking. CISSP® MENTOR PROGRAM – SESSION SIX 119 LECTURE Network Architecture and Design
- 121. Layer 1 Network Cabling - Coaxial Cabling • Coaxial cables are often used for satellite and cable TV service • More resistant to EMI, allows higher bandwidth and longer connections compared with twisted pair cable. • Two older types of coaxial cable are Thinnet and Thicknet, used for Ethernet bus networking. CISSP® MENTOR PROGRAM – SESSION SIX 120 LECTURE Network Architecture and Design
- 122. Layer 1 Network Cabling - Fiber Optic Network Cable • Uses light to carry information • Can be used to transmit via long distances: past 50 miles • Advantages are speed, distance, and immunity to EMI • Disadvantages include cost and complexity • Multimode fiber carrier • Uses multiple modes (paths) of light, resulting in light dispersion • Used for shorter distances • Single-mode fiber • Uses a single strand of fiber, and the light uses one mode (path) down the center of the fiber • Used for long-haul, high-speed networking • Multiple signals may be carried via the same fiber using Wavelength Division Multiplexing (WDM) • Multiple light “colors” are used to transmit different channels of information on the same fiber • Combined speeds of over a terabit/second can be achieved when WDM is used to carry 10-gigabits per color CISSP® MENTOR PROGRAM – SESSION SIX 121 LECTURE Network Architecture and Design
- 123. Layer 1 Network Cabling - Fiber Optic Network Cable • Uses light to carry information • Can be used to transmit via long distances: past 50 miles • Advantages are speed, distance, and immunity to EMI • Disadvantages include cost and complexity • Multimode fiber carrier • Uses multiple modes (paths) of light, resulting in light dispersion • Used for shorter distances • Single-mode fiber • Uses a single strand of fiber, and the light uses one mode (path) down the center of the fiber • Used for long-haul, high-speed networking • Multiple signals may be carried via the same fiber using Wavelength Division Multiplexing (WDM) • Multiple light “colors” are used to transmit different channels of information on the same fiber • Combined speeds of over a terabit/second can be achieved when WDM is used to carry 10-gigabits per color CISSP® MENTOR PROGRAM – SESSION SIX 122 LECTURE Network Architecture and Design
- 124. LAN Technologies and Protocols - Ethernet • Most common local area networking technology • Transmits network data in frames • Originally used a physical bus topology, and later added support for physical star • Describes Layer 1 issues such as physical medium and Layer 2 issues such as frames • Baseband (one channel) CISSP® MENTOR PROGRAM – SESSION SIX 123 LECTURE Network Architecture and Design
- 125. LAN Technologies and Protocols - Ethernet • Most common local area networking technology • Transmits network data in frames • Originally used a physical bus topology, and later added support for physical star • Describes Layer 1 issues such as physical medium and Layer 2 issues such as frames • Baseband (one channel) CISSP® MENTOR PROGRAM – SESSION SIX 124 LECTURE Network Architecture and Design
- 126. LAN Technologies and Protocols - Ethernet • Carrier Sense Multiple Access (CSMA) addresses collisions • Carrier Sense Multiple Access with Collision Detection (CSMA/CD): • 1. Monitor the network to see if it is idle • 2. If the network is not idle, wait a random amount of time • 3. If the network is idle, transmit • 4. While transmitting, monitor the network • 5. If more current is detected than sent, another station must also be sending a) Send Jam signal to tell all nodes to stop transmitting b) Wait a random amount of time before retransmitting • CSMA/CD is used for systems that can send and receive simultaneously, such as wired Ethernet • CSMA/CA (Collision Avoidance) is used for systems such as 802.11 wireless that cannot send and receive simultaneously • CSMA/CA relies on receiving an acknowledgement from the receiving station: if no acknowledgement is received, there must have been a collision, and the node will wait and retransmit CISSP® MENTOR PROGRAM – SESSION SIX 125 LECTURE Network Architecture and Design
- 127. LAN Technologies and Protocols - ARCNET & Token Ring • ARCNET (Attached Resource Computer Network) and Token Ring are two legacy LAN technologies • Pass network traffic via tokens • Possession of a token allows a node to read or write traffic on the network • No collisions - Predictable network behavior • ARCNET ran at 2.5 mbps and popularized the star topology • The last version of Token Ring ran at 16 mbps using a physical star/logical ring topology CISSP® MENTOR PROGRAM – SESSION SIX 126 LECTURE Network Architecture and Design
- 128. LAN Technologies and Protocols - FDDI • Fiber Distributed Data Interface • Legacy LAN technology • Logical network ring via a primary and secondary counter-rotating fiber optic ring • Secondary ring was typically used for fault tolerance • A single FDDI ring runs at 100 megabits • Uses a “token bus,” a different token-passing mechanism than Token Ring CISSP® MENTOR PROGRAM – SESSION SIX 127 LECTURE Network Architecture and Design
- 129. LAN Physical Network Topologies - Bus • Connects network nodes in a string • Each node inspects the data as it passes along the bus • Fragile: should the network cable break anywhere along the bus, the entire bus would go down CISSP® MENTOR PROGRAM – SESSION SIX 128 LECTURE Network Architecture and Design
- 130. LAN Physical Network Topologies - Tree • Also called hierarchical network • A network with a root node, and branch nodes that are at least three levels deep (two levels would make it a star) • The root node controls all tree traffic • Legacy network design; the root node was often a mainframe CISSP® MENTOR PROGRAM – SESSION SIX 129 LECTURE Network Architecture and Design
- 131. LAN Physical Network Topologies - Tree • Also called hierarchical network • A network with a root node, and branch nodes that are at least three levels deep (two levels would make it a star) • The root node controls all tree traffic • Legacy network design; the root node was often a mainframe CISSP® MENTOR PROGRAM – SESSION SIX 130 LECTURE Network Architecture and Design
- 132. LAN Physical Network Topologies - Ring • Connects network nodes in a ring • Logical ring, physical star • MAU/MSAU CISSP® MENTOR PROGRAM – SESSION SIX 131 LECTURE Network Architecture and Design
- 133. LAN Physical Network Topologies - Star • The dominant physical topology for LANs • First popularized by ARCNET, and later adopted by Ethernet • Each node is connected directly to a central device such as a hub or a switch CISSP® MENTOR PROGRAM – SESSION SIX 132 LECTURE Network Architecture and Design
- 134. LAN Physical Network Topologies - Star • The dominant physical topology for LANs • First popularized by ARCNET, and later adopted by Ethernet • Each node is connected directly to a central device such as a hub or a switch CISSP® MENTOR PROGRAM – SESSION SIX 133 LECTURE Network Architecture and Design
- 135. LAN Physical Network Topologies - Mesh • Interconnects network nodes to each other • Full mesh and partial mesh • Superior availability and are often used for highly available (HA) server clusters CISSP® MENTOR PROGRAM – SESSION SIX 134 LECTURE Network Architecture and Design
- 136. Technical, but not too technical. Please try to catch up in your reading. You’ve got Thursday (5/2) and the weekend off to catch up. • We left off on page 253 in the book. • Wednesday (5/1) we’ll finish this chapter and domain. • Come with questions! Have a great evening, talk to you Wednesday! CISSP® MENTOR PROGRAM – SESSION SIX 135 WE MADE IT THROUGH SESSION #6!