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Network Security Lecture 1 Notes

by: A. Dighe

Network Security Lecture 1 Notes 530

Marketplace > Iowa State University > CPR E > 530 > Network Security Lecture 1 Notes
A. Dighe
GPA 3.75

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About this Document

Notes cover the introduction to network security
Network Security
Jacobson Doug
Class Notes
Introductioton, Network, Security
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This 19 page Class Notes was uploaded by A. Dighe on Friday July 29, 2016. The Class Notes belongs to 530 at Iowa State University taught by Jacobson Doug in Summer 2016. Since its upload, it has received 14 views. For similar materials see Network Security in CPR E at Iowa State University.


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Date Created: 07/29/16
CprE 530 Advanced Protocols and Network Security Lecture 1 1 Today’s Topics • Introduction • Layered architecture • Key terms • Protocol Functions • OSI model • TCP/IP Model 2 Course Overview • Protocols • ProtocolImplementations • SSe eccuurriity IIsssuuees s • PerformanceIssues • Several programming assignments – packet sniffer – spam email 3 1840 1844 First Telegraph line 1861 Over 2200 telegraph offices 1875 First words on a telephone 1880 over 30,000 phones 1900 1900 over 600,000 phones 1920 over 11,000,000 phonesf Networking 1950s Point-to-point network to main frames 1960 1968 300 baud modem 1970 1969 ARPA NET(4 nodes) 1973 TCP/IP developmentT 1973 Ethernet was proposal in a Ph.D. Dissertation 1977 TCP/IP test bed 179UUCneett 1980 1980 ARPANETvirus (accidental) 1983 TCP/IP becomes the protocol for ARPANET 1984 over 1000 hosts 1986 NSFNETis started 1987 over 10,000 hosts 1988 Internet worm infects over 6,000 hosts 1989 over 100,000 hosts 1990 1991 WWW released by CERN 1992 over 1,000,000 hosts 1995 First ISPs started 4 1996 over 10,000,000 hosts 2000 Layered Architecture Protocol Application Application Network Services Potocol Network Services Communications Network 5 Layered Architecture SAP Service Access Points Layer N Protocol Layer N Protocol Layer N-1 Layer N-1 6 Layered Architecture • Brought about because of a need for standards • Layers: – take information from above (layer N-1) – and pass information below (layer N+1) • Thhe servces are povvded through theservice access points (SAPs) • Layer functionality is implemented through an entity • Each layer contains one or more entities which are responsible for providing services to the N+1 layer 7 Layered Architecture • In order for layers to carry out functions, they need to communicate • A layer N entity may need to communicate wiih annotheerlayeerN eentity,whhich doees noot reside on the same system, to provide the service. • The layer N entity uses the layer N-1 services to communicate with the remote layer N entity. 8 Layered Architecture Rcv_data Send_data Rcv_data Send_data Protocol A Layer Layer A A Send_packet Send_packet Rcv_packet Rcv_packet Layer Protocol B Layer B B 9 Layered Architecture • PROTOCOLS are the rules that have been defined for the layer N to layer N communication. • They represent extra information – example: saying “hello” on the telephone is a protocol • Protocols indicate when to send data, what language to use, etc. • A layer specification defines – what protocol it uses – what it expects as input (SAPs) – what functions it provides • Layer specifications allow multiple vendors to have the same functionality. – (ie: different ethernet card brands) 10 Protocol Data Unit • Protocol Data Unit (PDU) is the combination of data from the higher layer and the protocol or control information. • The protocol or control information created byy a layyer is calledd thee heaadderr. • Each layer adds it’s own header Data H1 D1 H1 D2 Layer 1 H2 H1 D1 H2 H1 D2 Layer 2 11 Control Information Encapsulation Data Data Layer Protocol A Layer A A AH Data AH Data AH Data AH Data Layer Protocol B Layer B B BH AH Data BH AH Data BHAH Data BHAH Data 12 Key Terms • The protocol defines the rules for PEER entity communication • Service Access Points (SAP) specify how the N entty commmuunicates wih the N-1 enntty. • Services are provided by the N entity to the N+1 entity • Functions are provided by the entity in coordination with the peer entity. 13 Basic Functions of a Protocol 1. Segmentation and reassembly: – Often physical media or error control issues dictate a maximum data size – Therefore the data muustbe divided ino smaalerr packets (Segmentation) – And eventually put back together (Reassembly) – Reassembly instructions are included in the header 14 Basic Functions of a protocol 2. Encapsulation: The addition of control information to the data element in the form of a header. • Address: The address of the sender and/or receiver. • Error Detection Code: Some sort of code is often included for error detection. • Protocol Control: Additional information needed to implement the protocol. 15 Basic functions of a protocol 3. Connection Control: – Connectionless Data Transfer • Data is ransferred withouttpriorcooordnaaion • No set path – Connection-oriented Data Transfer • A logical association, or Connection, is established between entities before any data is transferred • Example: telephone 16 Connection oriented • The three phases of Connection Control – request/connecctphasse – data transfer phase – terminate phase 17 Basic Functions of a protocol 4. Ordered Delivery – Pieces arrive in the same order as sent – Nottprovided by conneccionless prooccoss – Not required to be provided by Connection -oriented protocols, but it is common for most. (needed for file transfer) 18 Basic Functions of a protocol 5. Flow Control: – Technique for assuring that the ranssmiting entiy doessnootoveerwhelm aa receiving entity. – Flow Control is typically implemented in several layers. – Flow control is found in most connection- oriented protocols 19 Basic Functions of a protocol 6. Error Control: – Technique that allows a protocol to recover rom losstor damaagedd PDUUs. – Three mechanisms: • Positive acknowledgment • Retransmit after timeout • Error detection 20 Basic Functions of a protocol 7. Multiplexing: – Upward Multiplexing occurs when multiple higher level connections are multiplexed on a single lower level connection. Example: many applications utilize TCP (telnet, ftp, email) – Downward Multiplexing occurs when a single higher level connection is multiplexed on multiple lower level connections. (not as common) – Addressing is needed to support multiplexing 21 Multiplexing A1 Data A2 Data A3 Data Protocol A1 Layer Layer Layer Protocol A2 A1 A2 A3 PoocoA3 A A1 Data ProtocolB A2 LByer A3 Data BH A1 BH A2 BH A3 22 Protocol Example (part 1) Phone System Caller CentralOffices Called Party Pickup Receiver Time DialTone Dial Number Ring tone Ring the phone Pckup Receiver Stop ring tone Calling party Called party Conversion Answers (see diagram below) says something Either party Either party can hang up can hang up DialTone DialTone Dial Number Busy Signal 23 Protocol Example (part 2) Hello Is John there? Yes, this is John Conversation Good bye, John Good Bye 24 OSI Model • Application • Presentation • SSeesssion • Transport • Network • Data Link • Physical 25 Physical Layer • Responsible for the transparent transmission of bit streams across the physical interconnection of systems • Two configurations: – Point-to-point – Muutpontn • Physical layer must provide the data link entities with a means to identify the end point. • Physical connection can be Full Duplex or Half Duplex • Physical connection can be either bit serial or N bit parallel • Physical layer must deliver the bits in the same order in which they were offered for transmission by the Data Link Layer. 26 Data Link Layer • Main task is to shield higher layers from the characteristics of the physical transmission medium. • Should provide the higher layers with a reliable transmiissonn which is basicaly Error-Freee, alhoough errors may occur in the transmission on the physical connection. • Services provided should be independent of the data transmitted. • Data link layer connects two network entities in adjacent systems called Data link connection. 27 Data Link Layer • Each data-unit from the network layer is mapped into the data link protocol data unit along with the data link protocol information, and is called a Frame. • The data link layer must provide a method of recognizing he startannd end of heeFrramee. • Frames must be presented to the network in the same order they are received. • The data link layer should also implement Flow Control to prevent data overrun. 28 Network Layer • The primary responsibility of the network layer is to provide the transparent transfer of all data submitted by the transport layer to any transport entity anywhhere n the netwoork. • The network layer must handle the routing of data packets. • The network layer can be the highest layer in a device such as a gateway or router. • IP protocol 29 Transport Layer • Responsible for a reliable transparent data transfer between two session layer entities. • Transport connection is provide to the session entities independent of their location. • TTransport ayerrmuust optmiize resources whhiee maintaining a guaranteed quality of service. • Session layer requests a level of service and once the transport connection is provided with a certain quality of service it must be maintained unless notified of the change. • TCP protocol 30 Transport Layer • The transport layer is only concerned with transfer of data between session layers. It is not aware of the structure of the underlying layers or the topology. • The transport layer will use the network layer to get a network connection from one transport entity to another. • DDepeending on the quaaiy offthe network the tannsport ayerr may have to perform additional functions to offer the service. • The transport layer provides flow and error control. 31 Session Layer • The session layer is not concerned with the network. • The session layer’s goal is to coordinate the dialog between presentation layers • TThe seession ayyermuusttprovide the establshmmenntoff a session connection and the management of the dialog on that connection. • Example: An atm maintains a constant connection with a bank (transport service). The session starts when the user logs in. 32 Presentation Layer • The presentation layer provides the application layer with services related to the presentation of information in a form that is meaningful to the application entities. • Thhepresentaton ayyerprovdes the mechannsm forthe application layer to translate its data into a common format that can be translated by the peer application entity. • data format M1 network format data format M2 33 Application Layer • The highest layer and it provides a means for application processes to acccesss the OSSII stackk. • Provides both general services and application specific services. • This is what the user sees • Examples: telnet, ftp, web 34 Layered Network Model • Application software User • Presentation • Seession firmware hardware • Transport • Network OS • Data Link • Physical 35 TCP/IP vs OSI Application Presentation Application Sesson Transport Transport TCP Network IP Data link Physical Physical Network 36 TCP/IP Network Application Application TCP TCP IP IP IP IP Physical Physical Physical Physical Network Network Network Network End System End System Intermediate Intermediate System System 37 Non-layered Services Network Control and Management Applications Application TCP IP Network TCP/IP 4 layer model 38


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