CSCE 813 Internet Security TCP/IP

1. CSCE 813Internet SecurityTCP/IP Internet Security - Farkas

2. Reading Assignment Reading: R. Oppliger, Internet and Intranet Security, Artech House, Google Book, http://books.google.com/books/about/Internet_and_Intranet_Security.html?id=vtyowiyW9BkC, Chapter 2 Recommended Reading: CISCO: TCP/IP Technology, http://www.cisco.com/en/US/tech/tk365/technologies_white_paper09186a008014f8a9.shtml Internet Security - Farkas

3. Before the Internet • Isolated, local packet-switching networks • only nodes on the same network could communicate • Each network was autonomous • different services • different interfaces • different protocols Internet Security - Farkas

4. Before the Internet (cont.) • ARPANET: sponsored by Defense Advanced Research Projects • Agency (DARPA): • 1969: interconnected 4 hosts • 1970: host-to-host protocol: Network Control Protocol (NCP) • 1972: first application: e-mail Stanford Research Institute (SRI) Univ. of California at Santa Barbara (UCSB) Univ. of California at LA (UCLA) Univ. of Utah Internet Security - Farkas

5. Internet Connect Existing Networks: • ARPANET, Packet Radio, and Packet Satellite • NCP not sufficient Develop new protocol • 1970s: Transmission Control Protocol (Kahn and Vinton) • Based on packet switching technology • Good for file transfer and remote terminal access • Divide TCP into 2 protocols • Internet Protocol (IP): addressing and forwarding of packets • Transmission Control Protocol (TCP): sophisticated services, e.g., flow control, recovery • 1980: TCP/IP adopted as a DoD standard • 1983: ARPANET protocol officially changed from NCP to TCP/IP • 1985: Existing Internet technology • 1995: U.S. Federal Networking Council (FNC) defines the term Internet Internet Security - Farkas

6. Goals (Clark’88) Connect existing networks • Survivability • Support multiple types of services • Must accommodate a variety of networks • Allow distributed management • Allow host attachment with a low level of effort • Be cost effective • Allow resource accountability Internet Security - Farkas

7. Internet Challenge • Interconnected networks differ (protocols, interfaces, services, etc.) • Possibilities: • Reengineer and develop one global packet switching network standard: not economically feasible • Have every host implement the protocols of every network it wants to communicate with: too complex, very high engineering cost • Add an extra layer: internetworking layer • Hosts: one higher-level protocol • Network connecting use the same protocol • Interface between the new protocol and network Internet Security - Farkas

8. Layering • Organize a network system into logically distinct entities • the service provided by one entity is based only on the service provided by the lower level entity Internet Security - Farkas

9. Without Layering • Each application has to be implemented for every network technology! FTP HTTP SMTP Application Coaxial cable Fiber optic Transmission Media Internet Security - Farkas

10. HTTP With Layering • Intermediate layer provides a unique abstraction for various network technologies FTP SMTP Application Intermediate layer Coaxial cable Fiber optic Transmission Media Internet Security - Farkas

11. Layering • Advantages • Modularity – protocols easier to manage and maintain • Abstract functionality –lower layers can be changed without affecting the upper layers • Reuse – upper layers can reuse the functionality provided by lower layers • Disadvantages • Information hiding – inefficient implementations Internet Security - Farkas

12. ISO OSI Reference Model • ISO – International Standard Organization • OSI – Open System Interconnection • Goal: a general open standard • allow vendors to enter the market by using their own implementation and protocols Internet Security - Farkas

13. OSI Model Concepts • Service – says what a layer does • Interface – says how to access the service • Protocol – says how is the service implemented • a set of rules and formats that govern the communication between two peers Internet Security - Farkas

14. TCP/IP Protocol Stack Application Layer • Each layer interacts with • neighboring layers above • and below • Each layer can be defined • independently • Complexity of the networkingis hidden from the application Transport Layer Internetwork Layer Network Access Layer Internet Security - Farkas

15. OSI vs. TCP/IP • OSI: conceptually define: service, interface, protocol • Internet: provide a successful implementation Application Application Telnet FTP DNS Presentation Session TCP UDP Transport Transport IP Network Internet Datalink Host-to- network Packet radio LAN Physical Internet Security - Farkas

16. Network Access Layer • Responsible for packet transmission on thephysical media • Transmission between two devices that are physically connected • The goal of the physical layer is to move information across one “hop” • For example: Ethernet, token ring, Asynchronous Transfer Mode (ATM) Internet Security - Farkas

17. Internetwork Layer • Provides connectionlessand unreliable service • Routing (routers): determine the path a path has to traverse to reach its destination • Defines addressing mechanism • Hosts should conform to the addressing mechanism Internet Security - Farkas

18. IP Addresses • IP provides logical address space and a corresponding addressing schema • IP address is a globally unique or private number associated with a host network interface • Every system which will send packets directly out across the Internet must have a unique IP address • IP addresses are based on where the hosts are connected • IP addresses are controlled by a single organization - address ranges are assigned • They are running out of space! Internet Security - Farkas

19. Routing Protocols • Enable routing decisions to be made • Manage and periodically update routing tables, stored at each router • Router : “which way” to send the packet • Protocol types: • Reachability • Distance vector Internet Security - Farkas

20. The Domain Name System • Each system connected to the Internet also has one or more logical addresses. • Unlike IP addresses, the domain address have no routing information - they are organized based on administrative units • There are no limitations on the mapping from domain addresses to IP addresses Internet Security - Farkas

21. Domain Name Resolution • Domain Name Resolution: looking up a logical name and finding a physical IP address • There is a hierarchy of domain name servers • Each client system uses one domain name server which in turn queries up and down the hierarchy to find the address • If your server does not know the address, it goes up the hierarchy possibly to the top and works its way back down Internet Security - Farkas

22. Transport Layer • Provides services to the application layer • Services: • Connection-oriented or connectionless transport • Reliable or unreliable transport • Security (authenticity, confidentiality, integrity) • Application has to choose the services it requires from the transport layer • Limitations of combinations, e.g., connectionless and reliable transport is invalid Internet Security - Farkas

23. Application Layer • Provides services for an application to send and recieve data over the network, e.g., telnet (port 23), mail (port 25), finger (port 79) • Interface to the transport layer • Operating system dependent • Socket interface Internet Security - Farkas

24. Communication Between Layers Application Data Application layer Application layer Transport payload Transport layer Transport layer Network Payload Network layer Network layer Network layer Network layer Data Link layer Data Link layer Data Link layer Data Link layer Data Link Payload Host A Router Router Host B Internet Security - Farkas

25. Security -- At What Level? • Secure traffic at various levels in the network • Where to implement security? -- Depends on the security requirements of the application and the user • Basic servicesthat need to be implemented: • Key management • Confidentiality • Nonrepudiation • Integrity/authentication • Authorization Internet Security - Farkas

26. Network Access Layer Security • Dedicated link between hosts/routers  hardware devices for encryption • Advantages: • Speed • Disadvantages: • Not scaleable • Works well only on dedicates links • Two hardware devices need to be physically connected Internet Security - Farkas

27. Internetwork Layer Security IP Security (IPSec) • Advantages: • Overhead involved with key negotiation decreases <-- multiple protocols can share the same key management infrastructure • Ability to build VPN and intranet • Disadvantages: • Difficult to handle low granularity security, e.g., nonrepudation, user-based security, Internet Security - Farkas

28. Transport Layer Security • Advantages: • Does not require enhancement to each application • Disadvantages: • Difficult to obtain user context • Implemented on an end system • Protocol specific  implemented for each protocol Internet Security - Farkas

29. Transport Layer Security • Advantages: • Does not require enhancement to each application • Disadvantages: • Obtaining user context gets complicated • Protocol specific --> need to duplicated for each transport protocol • Need to maintain context for connection (not currently implemented for UDP) Internet Security - Farkas

30. Application Layer Security • Advantages: • Executing in the context of the user --> easy access to user’s credentials • Complete access to data --> easier to ensure nonrepudation • Application can be extended to provide security (do not depend on the operating system) • Application understand data --> fine tune security • Disadvantages: • Implemented in end hosts • Security mechanisms have to be implemented for each application --> • expensive • greated probability of making mistake Internet Security - Farkas

31. Application Example • E-mail client using PGP • Extended capabilities • Ability to look up public keys of the users • Ability to provide securiy services such as encryption/decrytion, nonrepudation, and authentication for e-mail messages Internet Security - Farkas