Protocol Architecture and Design: Understanding Layers and Communication in Networking, Slides of Data Communication Systems and Computer Networks

Download Protocol Architecture and Design: Understanding Layers and Communication in Networking and more Slides Data Communication Systems and Computer Networks in PDF only on Docsity! Chapter 2 Protocols and Architecture Docsity.com Need For Protocol Architecture • E.g. File transfer – Source must activate comms. Path or inform network of destination – Source must check destination is prepared to receive – File transfer application on source must check destination file management system will accept and store file for his user – May need file format translation • Task broken into subtasks • Implemented separately in layers in stack • Functions needed in both systems • Peer layers communicate Docsity.com Simplified File Transfer Architecture Computer X File transfer application Communication service module Network access module Network interface logic ommunications network Files and file transfer commands ae ee ee > Communications-related messages ee ee > Network interface logic Computer Y File transfer application Communication service module Network access module Docsity.com A Three Layer Model • Network Access Layer • Transport Layer • Application Layer Docsity.com Network Access Layer • Exchange of data between the computer and the network • Sending computer provides address of destination • May invoke levels of service • Dependent on type of network used (LAN, packet switched etc.) Docsity.com Protocol Architectures and Networks Applications ervice access point Transport Network address Network access Applications 1 2 -—{ }-—{ Transport Computer A Communications network Network access Applications Computer C 1 2 3 HK Transport Network access Computer B Docsity.com Addressing Requirements • Two levels of addressing required • Each computer needs unique network address • Each application on a (multi-tasking) computer needs a unique address within the computer – The service access point or SAP – The port on TCP/IP stacks Docsity.com Protocols in Simplified Architecture Computer X Computer Y Application Protocol Application Application [oy 8 8 8 8 8 0 eee eee ee ee > Transport Protocol Transport Pj------ ct err rr rr rrr r rrr >| ‘Transport ommunications network Network access Network access Network access protocol (®) Docsity.com Network access protocol Network PDU • Adds network header – network address for destination computer – Facilities requests Docsity.com Source X Application Transport ¥ Network Access Operation of a Protocol Architecture Record DSAP Transport PDU DHost DSAP = destination service access point DHost = destination host Packet Record DSAP Z > [DHost Destination Y Application zx Transport Network Access a 4 Docsity.com Standardized Protocol Architectures • Required for devices to communicate • Vendors have more marketable products • Customers can insist on standards based equipment • Two standards: – OSI Reference model • Never lived up to early promises – TCP/IP protocol suite • Most widely used • Also: IBM Systems Network Architecture (SNA) Docsity.com Application Provides access to the OSI environment for users and al O S | Lal provides distributed information services. Presentation Provides independence to the application processes from differences in data representation (syntax). Session Provides the control structure for communication between applications; establishes, manages, and terminates connections (sessions) between cooperating applications. Transport Provides reliable, transparent transfer of data between ena} points; provides end-to-end error recovery and flow contiol Network Provides upper layers with independence from the data transmission and switching technologies used to connec} systems; responsible for establishing, maintaining, and terminating connections. Data Link Provides for the reliable transfer of information across the physical link; sends blocks (frames) with the necessary synchronization, error control, and flow control. Physical Concerned with transmission of unstructured bit stream gv@er physical medium; deals with the mechanical, electrical, functional, and procedural characteristics to acggss the bm physical medium. y I The OSI Environment Outgoing PDU Construction Y AH| User Data DL-PDU Application Xp Application Session Transport Data Link Communications Path (e.g., point- to-point link, network) Physical Application Session Transport Data Link Physical Incoming PDU Reduction DL-PDU Docsity.com OSI as Framework for Standardization Layer 7 (Application) . . Service to Layer N+1 * s ¥ Protocol Total Layer N Layer a pith peer ‘Communication — entity Layer .V Function Decompose FY (modularity, oe information-hiding) . . Service from Layer -1 . Layer 1 OSI-wide standards ; (eg., network management, security) Docsity.com { (Physical) B S— Service Primitives and Parameters • Services between adjacent layers expressed in terms of primitives and parameters • Primitives specify function to be performed • Parameters pass data and control info Docsity.com Primitive Types REQUEST A primitive issued by a service user to invoke some service and to pass the parameters needed to specify fully the requested service INDICATION A primitive issued by a service provider either to: indicate that a procedure has been invoked by the peer service user on the connection and to provide the associated parameters, or notify the service user of a provider-initiated action RESPONSE A primitive issued by a service user to acknowledge or complete some procedure previously invoked by an indication to that user CONFIRM A primitive issued by a service provider to acknowledge or complete some procedure previously invoked by a request by the service user Docsity.com Timing Sequence for Service Primitives Service user Service provider Service user Service user Service provider Service user “és. Indication wee Indication Kanes (a) Confirmed Service (b) Nonconfirmed Service Docsity.com OSI Layers (3) • Session – Control of dialogues between applications – Dialogue discipline – Grouping – Recovery • Presentation – Data formats and coding – Data compression – Encryption • Application – Means for applications to access OSI environment Docsity.com Use of a Relay END RELAY END SYSTEM SYSTEM SYSTEM 7 fi - ee rr ee Application-layer protocol— — — — — — — — Py 7 ' 1 T ' 1 6, |mae -------- Presentation-layer protocal— — — — — — — — wy | 6 1 7 t ' 1 5) Me -------- Session-layer protocol? — — — — — — — — a 1 1 1 t ' 1 4 1 ff >>> oct Transport-layer protocol — — — — — — — — —m id 1 1 1 ' 1 31) [pf — — -Network— — ie ,------ . — — -Network— — -} | 3 ' 1 1 1 T 1 1 T ' 1 1 ' 2, |f@— — -Data Link- — 4 ! ' — — DataLink- — wy] 12 1 1 1 1 T 1 1 1 1 1 1 1 1 1 [f= — -Physical— — ot 1 — — “Physical — ey! 1 iv 1 1 \ I media for OSI ' $ ; ' Physical media for OSI U 4 wee ee ee eee See ee eee eee et Docsity.com TCP/IP Protocol Architecture • Developed by the US Defense Advanced Research Project Agency (DARPA) for its packet switched network (ARPANET) • Used by the global Internet • No official model but a working one. – Application layer – Host to host or transport layer – Internet layer – Network access layer – Physical layer Docsity.com Internet Layer (IP) • Systems may be attached to different networks • Routing functions across multiple networks • Implemented in end systems and routers Docsity.com Transport Layer (TCP) • Reliable delivery of data • Ordering of delivery Docsity.com Application Layer • Support for user applications • e.g. http, SMPT Docsity.com UDP • Alternative to TCP is User Datagram Protocol • Not guaranteed delivery • No preservation of sequence • No protection against duplication • Minimum overhead • Adds port addressing to IP Docsity.com Host A TCP/IP Concepts [\ Port or service access point (SAP) Oo Oo Logical connection TCP ne (TCP connection) = --077 Global network IP 4 > address Network Access Protocol #1 Logical connection Physical Subnetwork attachment (e.g., virtual circuit) pointaddress Router J , ae a IP NAP 1] NAP 2 Physical] Physical Network Access . Protocol #2 7 - Physical Docsity.com Addressing level • Level in architecture at which entity is named • Unique address for each end system (computer) and router • Network level address – IP or internet address (TCP/IP) – Network service access point or NSAP (OSI) • Process within the system – Port number (TCP/IP) – Service access point or SAP (OSI) Docsity.com Example Header Information • Destination port • Sequence number • Checksum Docsity.com Some Protocols in TCP/IP Suite MIME BGP FTP | | HTTP | | SMTP] |TELNET| | SNMP TCP UDP ICMP | | IGMP || OSPF | | RSVP IP BGP = Border Gateway Protocol OSPF = Open Shortest Path First FTP = File Transfer Protocol RSVP = Resource ReSerVation Protocol HTTP = Hypertext Transfer Protocol SMTP = Simple Mail Transfer Protocol \MP = Internet Control Message Protocol SNMP = Simple Network Management Protocol IP = Internet Group Management Protocol TCP = Transmission Control Protocol = Internet Protocol UDP = User Datagram Protocol D it MIME = Multi-Purpose Internet Mail Extension ocsity .com