Internet Security - Farkas1 CSCE 813 Internet Security TCP/IP

Internet Security - Farkas2 Reading Assignment Reading: R. Oppliger, Internet and Intranet Security, Artech House, Google Book, ecurity.html?id=vtyowiyW9BkC, Chapter 2 ecurity.html?id=vtyowiyW9BkC Recommended Reading: CISCO: TCP/IP Technology, paper09186a008014f8a9.shtml paper09186a008014f8a9.shtml

Internet Security - Farkas3 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 - Farkas4 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: Univ. of California at LA (UCLA) Stanford Research Institute (SRI) Univ. of California at Santa Barbara (UCSB) Univ. of Utah

Internet Security - Farkas5 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 - Farkas6 Goals (Clark’88) Connect existing networks 1. Survivability 2. Support multiple types of services 3. Must accommodate a variety of networks 4. Allow distributed management 5. Allow host attachment with a low level of effort 6. Be cost effective 7. Allow resource accountability

Internet Security - Farkas7 Internet Challenge Interconnected networks differ (protocols, interfaces, services, etc.) Possibilities: 1. Reengineer and develop one global packet switching network standard: not economically feasible 2. Have every host implement the protocols of every network it wants to communicate with: too complex, very high engineering cost 3. 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 - Farkas8 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 - Farkas9 Without Layering Each application has to be implemented for every network technology! SMTP FTPHTTP Coaxial cable Fiber optic Application Transmission Media

Internet Security - Farkas10 With Layering Intermediate layer provides a unique abstraction for various network technologies SMTP FTP Coaxial cable Fiber optic Application Transmission Media HTTP Intermediate layer

Internet Security - Farkas11 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 - Farkas12 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 - Farkas13 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 - Farkas14 TCP/IP Protocol Stack Application Layer Transport Layer Internetwork Layer Network Access Layer Each layer interacts with neighboring layers above and below Each layer can be defined independently Complexity of the networking is hidden from the application

Internet Security - Farkas15 OSI vs. TCP/IP OSI: conceptually define: service, interface, protocol Internet: provide a successful implementation Application Presentation Session Transport Network Datalink Physical Internet Host-to- network Transport Application IP LAN Packet radio TCPUDP TelnetFTPDNS

Internet Security - Farkas16 Network Access Layer Responsible for packet transmission on the physical 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 - Farkas17 Internetwork Layer Provides connectionless and 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 - Farkas18 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 - Farkas19 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 - Farkas20 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 - Farkas21 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 - Farkas22 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 - Farkas23 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 - Farkas24 Communication Between Layers Transport layer Network layer Data Link layer Network layer Data Link layer Network layer Data Link layer Network layer Transport layer Application layer Application Data Transport payload Network Payload Data Link Payload Host ARouter Host B

Internet Security - Farkas25 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 services that need to be implemented: Key management Confidentiality Nonrepudiation Integrity/authentication Authorization

Internet Security - Farkas26 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 - Farkas27 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 - Farkas28 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 - Farkas29 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 - Farkas30 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 - Farkas31 Application Example 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 messages