OSI Model_Unit 4_ Networking_Devices_ATM_ISDN.pptx

basics of the osi model fundamentals of the applications of the application layer

1. Communication Networks Prof. Yeshudas Muttu Assistant Professor Don Bosco College of Engineering, Goa Prof. Yeshudas Muttu

2. DATA COMMUNICATIONS Data communications are the exchange of data between two devices via some form of transmission medium such as a wire cable. Prof. Yeshudas Muttu

3. NETWORKS A network is a set of devices (often referred to as nodes ) connected by communication links . A node can be a computer, printer, or any other device capable of sending and/or receiving data generated by other nodes on the network . A link can be a cable, air, optical fiber, or any medium which can transport a signal carrying information. Prof. Yeshudas Muttu

4. Node 1 Node 2 Node 3 Node 4 Node 5 Link Network

5. PROTOCOLS A protocol consists of a set of rules that govern data communications. It determines what is communicated, how it is communicated and when it is communicated. Prof. Yeshudas Muttu

6. PROTOCOLS Prof. Yeshudas Muttu The key elements of a protocol are syntax, semantics and timing. Syntax Structure or format of the data so that other side can interpret it properly Indicates how to read the bits Semantics Interprets the meaning of the bits ( eg : grammar in language) Knows which fields define what action Timing When data should be sent and what Speed at which data should be sent or speed at which it is being received.

7. OSI Model Prof. Yeshudas Muttu Assistant Professor Don Bosco College of Engineering

8. International Standard Organisation (ISO) It is a body that gives all standards. One of the standards is OSI OSI is not a protocol Jus a framework that we use to define networking device It has 7 layers that have different functions but somehow interconnected. Open System Interconnection (OSI) Prof. Yeshudas Muttu

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10. Support Layers Network Support layers  Physically Sending data from one machine to another ( Hardware Part ) Physical, Datalink, Network layers User Support Layers  Software Part Prof. Yeshudas Muttu

11. The interaction between layers in the OSI model Prof. Yeshudas Muttu

12. The interaction between layers in the OSI model Prof. Yeshudas Muttu

13. An exchange using the OSI model Prof. Yeshudas Muttu

14. Physical Layer Just sends data from one device to another physically. Not bothered (1 – 1) Handles mechanical & Electrical Specifications Representation of bits Data Rate Synchronisation Line Configuration Topologies Transmission mode Prof. Yeshudas Muttu

15. Physical layer Prof. Yeshudas Muttu

16. Physical layer Prof. Yeshudas Muttu

17. The physical layer is responsible for movements of individual bits from one hop (node) to the next. Note Prof. Yeshudas Muttu

18. Datalink Layer Makes function of Physical Layer reliable. Confirms (1 – 1) Used within Network Eg : Switches Framing Physical addresses Flow Control Error Control Access Control Prof. Yeshudas Muttu

19. Data link layer Prof. Yeshudas Muttu

20. Data link layer Prof. Yeshudas Muttu

21. The data link layer is responsible for moving frames from one hop (node) to the next. Note Eg : Two PCs Connected together on same network Prof. Yeshudas Muttu

22. Network Layer If data is to be sent between two different networks, Network Layers plays important role. Eg : Router Entire message is divided into Packets Does not treat all packets together as one message. It considers one packet as one entity Logical Addressing Routing Prof. Yeshudas Muttu

23. Network layer Prof. Yeshudas Muttu

24. Network layer Prof. Yeshudas Muttu

25. The network layer is responsible for the delivery of individual packets from the source host to the destination host. Note Prof. Yeshudas Muttu

26. Transport Layer Finds relation between the packets, brings them together & reforms the message. Service Point Addressing (Same Processes) – responsible for getting entire message correctly on to the process. Connection Control Connection less (every packet is different but when it receives, puts them in proper order) Connection oriented (establishes one link & then distributes) Flow Control & Error Control (end to end) Prof. Yeshudas Muttu

27. Transport layer Prof. Yeshudas Muttu

28. Transport layer Prof. Yeshudas Muttu

29. The transport layer is responsible for the delivery of a message from one process to another. Note Prof. Yeshudas Muttu

30. Session Layer Allows system to enter into dialog Dialog Control (start up a process) – commn between two processes in half duplex or full duplex Synchronisation (big message divided into frames) – allows a process to add check points. Prof. Yeshudas Muttu

31. Session layer Prof. Yeshudas Muttu

32. Session layer Prof. Yeshudas Muttu

33. The session layer is responsible for dialog control and synchronization. Note Prof. Yeshudas Muttu

34. Presentation Layer Translation (Common Format) Encryption Compression Prof. Yeshudas Muttu

35. Presentation layer Prof. Yeshudas Muttu

36. Presentation layer Prof. Yeshudas Muttu

37. The presentation layer is responsible for translation, compression, and encryption. Note Prof. Yeshudas Muttu

38. Application Layer Applications that we use provide services to the user Services provided: Network Virtual Terminal – software that allows a user to log on to the host File Transfer, access & Management (FTAM) – allows user to access files in a remote computer Mail Services – basis for email forwarding & storage Prof. Yeshudas Muttu

39. Application layer Prof. Yeshudas Muttu

40. Application layer Prof. Yeshudas Muttu

41. The application layer is responsible for providing services to the user. Note Prof. Yeshudas Muttu

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43. Summary of layers Prof. Yeshudas Muttu

44. Networking & Internetworking Devices Prof. Yeshudas Muttu Assistant Professor Don Bosco College of Engineering

45. Network Two or more devices connected together to share data or resources. LAN = Local Area Network More cabling Overcrowd places Repeaters  to increase the coverable distance Bridge  Traffic Management Prof. Yeshudas Muttu

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47. Internetworking devices Two or more separate networks are connected. Many LANs into an internetwork Routers and Gateways Used to connect individual networks Prof. Yeshudas Muttu

48. PAN (Personal Area Network) Local Area Network Prof. Yeshudas Muttu WAN (Wide Area Network)

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51. Each of them interacts with protocols at different levels of OSI Prof. Yeshudas Muttu

52. Repeaters Act only on electrical components of a signal & are therefore active only at Physical Layer. Prof. Yeshudas Muttu

53. Bridges Utilize addressing Protocols Affect flow control of Single LAN Most active at Data Link Layer Prof. Yeshudas Muttu

54. Routers Provides link for two separate but same type LANs. Most active in Network Layer. Prof. Yeshudas Muttu

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59. Gateways Provide link two separate but different type LANs. Most active in Network Layer. Prof. Yeshudas Muttu A gateway is a hardware device that acts as a "gate" between two networks . It may be a router, firewall, server, or other device that enables traffic to flow in and out of the network.

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62. Prof. Yeshudas Muttu Switch

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64. Prof. Yeshudas Muttu HUB

65. Prof. Yeshudas Muttu HUB

66. Hub Switch Router Works on Physical Layer of OSI Model Works on Data Link Layer of OSI Model works on Network Layer of OSI Model Broadcast Device Multicast Device Router is a routing device use to create route for transmitting data packets Used to connect device in the same network Used to connect devices in the same network Used to connect two or more different network. sends data in the form of binary bits sends data in the form of frames sends data in the form packets Hub only works in half duplex: Only one device can send data at a time Switch works in full duplex: Multiple devices can send data at the same time Router works in full duplex: Multiple devices can send data at the same time Hub does not store any MAC address or IP address Switch store MAC Address Router stores IP address Difference Between Hub, Switch and Router Prof. Yeshudas Muttu

67. Firewall Prof. Yeshudas Muttu

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72. Connecting devices and OSI model Prof. Yeshudas Muttu

73. Repeaters Regenerator Signal carrying information within a network can travel fixed distance b4 attenuation. But later, if signal becomes weak, repeater needs to be placed in a network. It regenerates the original bit pattern Also, puts it back onto the link Prof. Yeshudas Muttu

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75. Repeater operates on physical layer. It allows to extend the physical length of the network. It doesn’t change the functionality of network. A repeater forwards every frame; it has no filtering capability. Prof. Yeshudas Muttu

76. A repeater in OSI model Prof. Yeshudas Muttu

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78. Not an amplifier A repeater does not amplify the signal, it regenerates it. bit for bit copy remove noise, but do not correct/detect error Recover the signal strength Prof. Yeshudas Muttu

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80. The location of the repeater on the link is vital: It must be placed so that a signal reaches it before any noise changes the meaning of the carried information. A little noise can alter the precision of a bit voltage without destroying its identity; if the corrupted bit travels much further, voltage level changes drastically; & the original voltage is unrecoverable. A repeater placed on the line before this complete lost takes place, so that we can recover the original bit patterns. Prof. Yeshudas Muttu

81. Advantages Of Repeaters Extend network physical distance Do not seriously affect network performance Special repeaters connect different media Copper to fiber Prof. Yeshudas Muttu

82. Disadvantages Of Repeaters Cannot connect different network architectures Token Ring and Ethernet (Star) Cannot reduce network traffic Repeaters do not filter data Do not segment (divide) the network Repeat everything without discrimination Number of repeaters must be limited Prof. Yeshudas Muttu

83. Bridges Prof. Yeshudas Muttu

84. Bridges Operate in both physical and data link layer of OSI Can divide a large network into smaller segments Can relay frames between two originally separate LANs Keep the traffic for each segment separated, filtering the traffic. They are useful to keep the congestion low Prof. Yeshudas Muttu

85. Bridges… Prof. Yeshudas Muttu

86. The bridge will check the physical address of the destination and forwards the new copy only to the segment to which the address belongs It reads the address contained in the frame and it compares it against an internal table with all the addresses of the stations on both segments. When it finds a first match, it discovers to which segment the station belongs and relays the packet only to that segment. Prof. Yeshudas Muttu

87. Bridges… Prof. Yeshudas Muttu

88. The bridge will block a packet from station A addressed to station D from crossing into the lower segment. The bridge will allow a packet from station A to station G to cross into the lower segment and relays it to the entire lower segment where it is received by station G Prof. Yeshudas Muttu

89. Simple bridge Links two segments and contains a table that lists the addresses of all the stations included in each of them Addresses must be entered manually (before a simple bridge can be used, an operator has to sit down and enter the addresses of every station) Prof. Yeshudas Muttu

90. Whenever a new station has been added, the table has to be modified; when a station is removed, the table has to be modified, the newly invalid address has to be deleted The bridge is simple to build and inexpensive to manufacture but installation and maintenance are time consuming, probably more expensive than the price saving resulted out of the cheap manufacturing cost Simple bridge Prof. Yeshudas Muttu

91. Multiport bridge Connects more than two LANs For this bridge, there are three tables, each holding the physical addresses of stations reachable through the corresponding port Prof. Yeshudas Muttu

92. Transparent bridge/ Learning bridge This learning bridge builds its table of station addresses on its own as it performs bridge functions When first installed, its table is empty; as it encounters each packet, it looks at both the destination and the source addresses. It checks the destination and decides where to send the packet; if it doesn’t recognize yet the destination address, it sends the packet on all of the ports Prof. Yeshudas Muttu

93. It uses the source address to build its table; with the first packet transmitted by each station, it learns the segment associated with that station Continuing this process even after each station has been learned, it assures that it is self-updating Prof. Yeshudas Muttu

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95. Loop Problem & its Avoidance Transparent bridges work fine as long as there are no redundant bridges in the system. Bridges are normally installed redundantly, which means that two LANs may be connected by more than one bridge. In this case, if the bridges are transparent bridges, they may create a loop, which means a packet may be going round and round, from one LAN to another and back again to the first LAN. To solve the looping problem, the IEEE specification requires that bridges use the spanning tree algorithm to create a loop less topology. Source Routing: Source of the packet decides to which bridge to go before reaching the destination (Selection of Bridge by Source) Prof. Yeshudas Muttu

96. Bridges connecting different LANs Frame format – frames from different LANs have different formats (i.e. Ethernet frame and Token Ring frame) Payload size – the size of the data that can be encapsulated in a frame varies from protocol to protocol (i.e. Ethernet has 1500 + headers while Token Ring has 4500 + headers) Data rate – different protocols use different data rates (i.e. 10 Mb/s for Ethernet and 16Mb/s for Token Ring) Address bit order – the bit order of addresses in different types of LANs is not the same (i.e. a bridge should reverse an address if it is connecting an Ethernet LAN to a Token Ring LAN) Other issues: collision, acknowledgements, priority, etc… Prof. Yeshudas Muttu

97. Routers Relay packets among multiple interconnected networks and operate at physical, data link and network layer of OSI model. Have access to network layer addresses and have two or more networks at the same time. Prof. Yeshudas Muttu

98. Routers A packet sent from a station on one network to a station on a neighboring network, goes first to the jointly held router, which forwards it to the destination network. If the router is not connected to both source and destination network, then the sending router transfers the packet across one of its connected networks to the next router, in the direction of the destination, and so on, until the destination is reached Prof. Yeshudas Muttu

99. Issues involved in Routers Thru’ which path the data to be sent Non – Adaptive Routing Adaptive Routing Packet Life time or Time to live (TTL) - avoids looping & bouncing

100. TTL A says shortest Path to C is thru’ B B4 ‘B’ Rxes , it comes to knw tht its link to C is disabled. B updates itself & Finds tht shortest path to C is thru’ A A has not Txed the info about B & C links & still believes that best path is thru’ B. B sends A  A sends B………………… This is looping & Bouncing In TTL, each packet is given lifetime.

101. Gateways/ Firewall Operates in all 7 layers in OSI model. Protocol converter Router  transfers, accepts, relays packets only across a network using similar protocols. Gateway  can accept a packet formatted for one protocol & convert it to a packet formatted for other protocol Prof. Yeshudas Muttu

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103. Gateways It is software installed within a router. It understands the protocols linked to each network by a router. Header & Trailer Packets are necessarily modified. In other cases, gateway must adjust the data rate, size, format also. Prof. Yeshudas Muttu

104. SNA(System Network Architecture) network (IBM) Netware network (Novell) Prof. Yeshudas Muttu

105. What is difference between? Bridge: device to interconnect two LANs that use the SAME logical link control protocol but may use different medium access control protocols. Router: device to interconnect SIMILAR networks, e.g. similar protocols and workstations and servers Gateway: device to interconnect DISSIMILAR protocols and servers, like Macintosh and IBM LANs and equipment Switch: device to allow different nodes of a network to communicate directly with each other. Allow several users to send information over a network at the same time without slowing each other down. Prof. Yeshudas Muttu

106. Asynchronous Transfer Mode (ATM) Prof. Yeshudas Muttu

107. Introduction T he different types of traffic and their demands on a communication channel: Voice Its generation is asynchronous (a speaker may speak anytime) Its transmission must be synchronous (once the message starts, it must flow continuously as it is spoken) The bandwidth required for a voice conversation in digital communication is relatively small and constant (64K) The signals may contain a high degree of error and the information can still be retrieved correctly Prof. Yeshudas Muttu

108. Introduction T he different types of traffic and their demands on a communication channel: Video The generation is synchronous (continuous) Its transmission is synchronous (you wouldn't like to see first a half a head, then a pair of feet, then the rest of the image of a person) The bandwidth required is variable and it could range from under 64 Kbps to several Mbps in the same session. (Humans require 25-30 images/second and sometimes, with a sudden change in scenery and a lot of excitement before the camera, there is a tremendous amount of information to be sent in an awfully short time; some other times only very small changes between consecutive screens need be transmitted) Error control should be tight - otherwise the wrong information on the monitor may trigger severe wrongful actions (security misinformation, wrong reaction of robots, etc .) Prof. Yeshudas Muttu

109. Introduction The different types of traffic and their demands on a communication channel: Data Its generation could be either asynchronous (text) or synchronous (telemetry) Its transmission in general can be asynchronous (data typically can wait patiently in buffers), so no special timing relationship between the transmitter and the receiver is required The amount of bandwidth varies enormously from a few bits per second to billions of bits per second The information is extremely error-sensitive, so extreme caution must be exercised in transmission and error control must be very tight. Prof. Yeshudas Muttu

110. ATM Cell relay protocol ✓ Adopted by ITU-T ✓ International Telecommunication Union-Telecommunications Standards Section Prof. Yeshudas Muttu

111. ATM ✓ Cell-switching and multiplexing technology. ✓ Combines the benefits of – Circuit switching ✓(guaranteed capacity and constant transmission delay) Packet switching ✓ (flexibility and efficiency for intermittent traffic). ✓ It provides scalable bandwidth from a few megabits per second (Mbps) to many gigabits per second ( Gbps ). Prof. Yeshudas Muttu

112. Circuit Switched Network Prof. Yeshudas Muttu

113. Packet Switched Network Prof. Yeshudas Muttu

114. Packet Switched Network Prof. Yeshudas Muttu

115. Why ATM ? Optical fibre offered new transmission media less susceptible to noise with very high data rates. • Existing system not utilising its full potential. • A new system is required which  Prof. Yeshudas Muttu

116. Design Goals for ATM High BW Txn media having lesser P e (X.25, frame relay) Interfacing capability with existing systems for packet Txn Cost effective implementation Connection oriented to ensure accuracy & predictability More functionality in hardware than in software for higher speed. Prof. Yeshudas Muttu

117. PROBLEMS WITH EXISTING SYSTEM Different protocols use packets of different sizes and different bit distribution. • More complex network result in larger header. • Data field should be increased to increase Data : Header ratio. • Field is wasted in absence of large data. • VISIBLE REMEDY: Variable packet size Prof. Yeshudas Muttu

118. PROBLEMS WITH VARIABLE PACKET SIZE Unpredictable traffic. • Switches, multiplexers and routers need elaborate S/W to manage variable packet sizes. • Large header information. • Inter-networking different n/ ws is slow, expensive and sometimes impossible. • Difficult to provide consistent data rate. • A smaller packet waiting on a larger packer will be severely delayed… Prof. Yeshudas Muttu

119. Multiplexing Using Different Packet Sizes Prof. Yeshudas Muttu

120. Cell Switching Concept Cell = fixed size block of Info ATM uses Asynchronous TDM Cells coming from different sources will reach the destination more quickly Advantages: None suffers long delay coz of high speed & small cell size. Switching & Mux by h/w at cell level makes implementation inexpensive Disadvantages: Overhead is more ( 5/53 = 9.4%) Delays in packetization (speaking on telephone) Prof. Yeshudas Muttu

121. ATM SOLUTION -- ATM Network Packet switched network. • Supports multiplexing of multiple logical connections over single physical channel. • No error/flow control at intermediate stages. • Can serve as LAN or WAN backbone to existing system without major change. • Other protocol packets can be transformed to ATM cell. • Can deliver voice, data and video. Prof. Yeshudas Muttu

122. ATM SOLUTION -- ATM Network Uses ATM switch in star. Communication via switch. Network is highly scalable. Extremely high data rates – 1.544Mbps to 155Mbps. 2 OFC between host and switch for full duplex line. ATM caters to all requirements of data, audio and video. Prof. Yeshudas Muttu

123. ATM SOLUTION -- ATM Network Audio – Real time and fast. Data – Very high accuracy Video – Very high bandwidth, to create continuity. Size cannot be large and variable. Fixed size cells of 53 octets (bytes). 5 octet headers + 48 octets data. Achieves higher data rates. Avoids transmission delays. Prof. Yeshudas Muttu

124. No Delay in Multiplexing Small and Equal size cells. Delay suffered is very small and uniform. Due to high speed of link and small cell size, packet appear to reach almost continuously. Very suitable for video and audio. Switching and MUX can be implemented in H/W. Prof. Yeshudas Muttu

125. ATM Multiplexing (Asynchronous) Prof. Yeshudas Muttu

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127. Architecture of an ATM Network UNI – user-to-network interface NNI – network-to-network interface User access devices (End points) are connected through UNI to the switches inside network. Switches are connected through NNIs. Prof. Yeshudas Muttu

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129. TP, VPs, and VCs TP – Transmission path VP – Virtual path VC – Virtual circuit Prof. Yeshudas Muttu

130. Architecture of an ATM Network Connection accomplished through TPs, VPs and VCs. ■ TP – Physical connection (wire, cable, satellite ..) between an end point and a switch or between two switches.. ■ VP –set of connections between two switches. ( combination of VCs bundled together because parts of their path are same) ■ VCs – All cells belonging to a single message follow same virtual circuit, in original order till destination. (logical connections) Prof. Yeshudas Muttu

131. ATM Network Analogy ■ Two switches as two cities. ■ TP - Set of all highways that directly connects two highways. ■ VP – Highway that connects two cities. ■ VCs – Lanes of a highway Prof. Yeshudas Muttu

132. VPs and VCs Prof. Yeshudas Muttu

133. ■ 8 end points communicating using 4 VCs. ■ Two VCs share same VP from switch I to switch III, bundled together in one VC. ■ Other two VCs share same path from switch I to switch IV, hence bundled together in one VP. Prof. Yeshudas Muttu

134. Advantages of Virtual Paths Simplified Architecture Increased network performance & reliability Reduced processing & short connection set up time Enhanced network services Prof. Yeshudas Muttu

135. Connection Identifiers VPI – Virtual path identifier VCI – Virtual circuit identifier Prof. Yeshudas Muttu

136. Connection Identifiers ■ ATM gives hierarchical identifier for two levels. ■ Virtual path identifier (VPI)- defines specific VP ■ Virtual circuit identifier (VCI)- defines a particular VC inside the VP. ■ Virtual connection is identified by pair of VPI and VCI together. ■ UNI – VPI is 8 bits, VCI is 16 bits. (Total 24) ■ NNI – VPI is 12 bits, VCI is 16 bits (Total 28) Prof. Yeshudas Muttu

137. Virtual Connection Identifiers in UNIs and NNIs Prof. Yeshudas Muttu

138. Cells Basic data unit in ATM network It is 53 bytes long with 5 bytes allocated to header & 48 bytes carrying payload. User data may be less than 48 bytes Most of header is occupied by VPI & VCI that defines virtual connection thru’ which a cell shud travel from end pt to a switch or from one switch to another switch. Prof. Yeshudas Muttu

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140. Connection Establishment & Release ATM uses two kind of connections Permanent VC (PVC) Switched VC (SVC) Prof. Yeshudas Muttu

141. PVC It is the connection established between two end points by the network provider . VPIs & VCIs are defined for permanent connections Values are entered for the tables of each switch Prof. Yeshudas Muttu

142. SVC Here, each tym an end point wants to make connection with another end point, a new VC shud be established. ATM cannot do job by itself, but needs network layer addresses & services of another protocol. The signalling mechanism of this other protocol makes a connection request using the network layer addresses of the two end points. Actual mechanism depends on network layer protocol. Prof. Yeshudas Muttu

143. Integrated Services Digital Network (ISDN) Prof. Yeshudas Muttu

144. GOAL To use existing infrastructure of telephone lines and networks and to be able to transmit ✓ Voice ✓ Digital data ✓ Other services like reservations, alarm etc. To form a WAN that provides universal end-to-end connectivity over digital media, by integrating all transmission services into one without adding new links. Prof. Yeshudas Muttu

145. ISDN Services Prof. Yeshudas Muttu

146. ISDN Services Bearer Services: Provides means to transfer information between users without network manipulating content of information. Belongs to first 3 layers of OSI model. Can be provided using circuit-switched, packet-switched, frame-switched or cell-switched networks. Tele-services: Network may change or process the data. Corresponds to layers 4-7 of OSI model. Rely on the facilities of bearer services. designed to accommodate complex user needs. Includes telephony, teletext , telefax , telex, teleconferencing. Supplementary Services: Provides additional functionality to above. E.x . Reverse charging, cell waiting, message handling.. Prof. Yeshudas Muttu

147. History: Voice Communication over an Analog Telephone Network Used for transmission of analog information in the form of voice. Local loops connecting the subscriber’s handset to telephone company’s central office were also analog. Prof. Yeshudas Muttu

148. History: Voice and Data Communication over an Analog Telephone Network With advent of digital processing, subscribers needed to exchange data as well as voice. Modems were developed to allow digital exchanges over existing analog lines. Prof. Yeshudas Muttu

149. History: Analog and Digital Services over the Telephone Network To reduce cost and improve performance, digital technologies added with backward compatibility. Three types of customers: Traditional costumers using local loops for analog purposes most prominent. Customers using analog facilities for digital information via modem. Customers using digital facilities for digital information. Prof. Yeshudas Muttu

150. IDN: Integrated Digital Network Prof. Yeshudas Muttu

151. IDN: Integrated Digital Network To meet need for packet-switched and circuit-switched networks. A combination of networks available for different purposes. Access to these networks by digital pipes( time-multiplexed channels sharing very high speed paths). Customers can use their local loops to transmit both voice and data to telephone central office. Central office directs these calls to appropriate digital networks via digital pipes. Prof. Yeshudas Muttu

152. ISDN Prof. Yeshudas Muttu

153. ISDN Integrates customer services with IDN. Fully digital services are more efficient and flexible. Need to replace analog local loop with digital subscriber loop. Voice transmission can be digitised at source. Possible to send data, voice, image etc. over it. With all services digital, flexibility allows services available on demand. Allows all connections in home or building via single interface. Digital pipes allow different transmission rates and support different subscriber needs. Prof. Yeshudas Muttu

154. ISDN Architecture – Digital Bit Pipe Bidirectional conceptual pipe through which bits flow between end user and CO/ ISDN exchange. Bits may correspond to any of the services. Supports TDM Two categories defined. Home user – Low bandwidth Business user – High bandwidth Total BW divided into Channels. Each channel equal to one home user channel. Business users can have multiple bit pipe each having multiple channels. Prof. Yeshudas Muttu

155. ISDN Architecture – ISDN channel Type BEARER CHANNEL B 64 kbps data rate. Used for digitized voice, data or other low data rate information. Full duplex. 8000 samples/s X 8 bits/sample = 64kbps. One B channel per subscriber per exchange of information. Subscriber will contend for B channel. For higher data rates , two B channel can be combined to give 128kbps. Prof. Yeshudas Muttu

156. DATA CHANNEL D Contrast to name, does NOT carry data. Carries controlling signals as establishing a call, ringing, call interrupt etc. Carries control signals for all using Out-band signalling. (Protocol-Signalling system Number 7, SS7) 16 / 64 kbps Subscriber secures a B connection by using D channel . In case of no signalling, it can be used to carry data as videotext, tele -text, emergency services alarms etc.. ISDN Architecture – ISDN channel Type Prof. Yeshudas Muttu

157. ISDN Architecture – ISDN channel Type HYBRID CHANNEL H Used at high BW requirements. 384 / 1536 / 1920 kbps. Used for video, video-conferencing, high speed data/audio etc. Can be sub divided as per need. Can be used as B channel for high BW needs. Prof. Yeshudas Muttu

158. ISDN Interfaces - BRI Basic rate interface, used for home users. Specifies a digital pipe with 2 B channels and 1 D channel (16kbps). 2 X 64 + 16 = 144kbps In addition, BRI services requires 48 kbps of management overheads. Total data rate - 192 kbps. User can use one B channel for a call and other for browsing. Both B channel can be combined for faster connection to internet. Prof. Yeshudas Muttu

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160. ISDN Interfaces - PRI Primary rate interface, used for business users. Specifies a very big digital pipe with 23 B channels and 1 D channel (64kbps). In addition, BRI services requires 8 kbps of management overheads. 23 X 64 + 64+ 8 = 1.544Mbps. A User can use more than one B channel. Prof. Yeshudas Muttu

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162. Functional Grouping Prof. Yeshudas Muttu

163. Functional Grouping--Terminal Equipment TE1 ➢ All ISDN equipments as digital telephone, digital fax, digital voice and data terminals ➢ Can be directly connected to ISDN. TE2 ➢ All non-ISDN equipments as normal analog telephone, analog fax etc. ➢ Helps backward compatibility. ➢ Cannot be directly connected to ISDN. Prof. Yeshudas Muttu

164. Functional Grouping--Network Termination NT1 ➢ Controls electrical and physical termination of ISDN at user’s premise. ➢ Analogous to physical layer . ➢ Organises data streams into frames and back. ➢ Though not a MUX, it interleaves bytes to act like a MUX. ➢ Connected to ISDN using twisted pair wires of telephone network. ➢ Can connect up to 8 devices at one premise . ➢ It supports multiple channels using TDM Prof. Yeshudas Muttu

165. Functional Grouping--Network Termination NT2 ➢ For large business, need to support more telephone conversation at a time.. ➢ Analogous to PBX ( Private Branch Exchange ). ➢ It multiplexes multiple incoming links to be given to NT1. ➢ Works in three layers. ➢ Multiplexing - layer 1 ➢ Flow control - layer 2 ➢ Packetizing – layer 3 Prof. Yeshudas Muttu

166. Functional Grouping--Terminal Adapter TA ➢Converts information from non-ISDN equipments to ISDN format. ➢ Acts as converter ➢ Kept at user’s premise. Prof. Yeshudas Muttu

167. Reference points Prof. Yeshudas Muttu

168. What is a reference point ? It defines the interface between two functional groupings. Indicates how a device from two functional grouping should be connected, how they will exchange data, etc. Prof. Yeshudas Muttu

169. Reference – R defines a connection between TE2 & TA. Provides non – ISDN interface between the user equipment that is not ISDN compatible & adapter equipment Prof. Yeshudas Muttu

170. Reference – S Defines connection between TE or TA & NT1 or NT2 Corresponds to interface of individual ISDN terminals. It separates user terminals equipment from network related communication functions. Prof. Yeshudas Muttu

171. Reference – T Defines connection between NT1 & NT2 Corresponds to minimal ISDN network termination at customers premises It separates the network providers equipment from the users equipment Prof. Yeshudas Muttu

172. Reference – U Defines the interface between an NT1 & ISDN office Prof. Yeshudas Muttu

173. ISDN Layers 7 layer OSI model cannot be applied to ISDN because… ISDN specifies two different channels (B and D) with different functionalities requiring different protocols. B channel - user to user communication. D channel - user to network signalling. ISDN also differs from OSI in management needs. Global integration, maintaining the flexibility required to keep the network truly integrated using public services requires huge management. ITU-T has devised an expanded model for ISDN layers in defining three separate planes: User plane, Control plane, Management plane. Prof. Yeshudas Muttu

174. ISDN Layers Prof. Yeshudas Muttu

175. ISDN Layers At physical layer , B and D channels are same, use either BRI/PRI interface. At data link layer , B/D channel uses LAPB/LAPD (Link Access Protocol). At network layer , B channel has many options in connecting to circuit switched/ packet switched/Frame relay/ATM networks. User plane options for layers 4 through 7 is left to user. Prof. Yeshudas Muttu

176. Simplified Layers of ISDN Prof. Yeshudas Muttu

177. Physical Layer Specified by ITU-T standard: I.430 for BRI and I.431 for PRI access. Primary aspects defined by these standards are: The mechanical and electrical specifications of interface R, S, T and U. Encoding. Multiplexing channels for BRI and PRI digital pipes. Power supply. Prof. Yeshudas Muttu

178. Eg : Physical Layer BRI Interface-U Between NT1 and ISDN exchange. Single pair twisted pair cable in each direction. 2 binary 1 quaternary Encoding, 4 voltage levels for two bits 00, 01, 10 and 11. Lowers baud rate, high efficiency in using available BW. 2B/1Q Encoding Prof. Yeshudas Muttu

179. BRI Frame Each B channel is sampled twice and D channel four times in a frame. 12 Overhead bits are for framing and synchronizing. 48 bits long frame helps in making ATM cell. Prof. Yeshudas Muttu

180. BRI Topology Prof. Yeshudas Muttu

181. BRI Topology A bus or a Star based on distance of devices from NT1. Point-to-point Bus connection —1000 meters maximum. Multipoint Bus connection — less than 200meters if devices are spaced apart. Distance limitation to ensure synchronization. Propagation delay between first and last device can deteriorate synchronisation during multiplexing. If devices are clustered, distance can be 500 meters. Propagation delay will be almost same for all. Star topology link can be 1000 meters long. Prof. Yeshudas Muttu

182. BRI Topology Maximum 8 devices. Only 2 devices can access B channel at a time, one exchange per channel. All devices can contend for D channel using CSMA ( Carrier-sense multiple access: a node verifies the absence of other traffic before transmitting on a shared transmission medium) . Winning device then requests for B channel. On availability of B channel, connection is made by D channel for user to send data. Prof. Yeshudas Muttu

183. Physical Layer for PRI 23 B channels and 1 D channel. Interface used are R, S, T, U. R and S standards same as BRI. T standard is identical to S standard with substitution of B8ZS encoding. U interface is also same except PRI rate is 1.544 Mbps instead of 192 Kbps of BRI. Prof. Yeshudas Muttu

184. PRI Interfaces T interface – Same as S interface. Encoding is B8ZS Prof. Yeshudas Muttu

185. PRI Frame and Topology B and D channels multiplexed using synchronous TDM to create PRI frame. PRI frame samples each B channel and D channel only once per frame. Connection and topology between devices and NT2 can be same as that described between devices to NT1 in BRI. Depending on specific application it can change as — If NT2 LAN, topology specified by LAN. If NT2 PBX, topology specified by PBX… Link from NT2 to NT1 must always be point to point. Prof. Yeshudas Muttu

186. PRI Frame Prof. Yeshudas Muttu

187. DATA LINK LAYER B and D channels use different data link protocols. Link Access Protocol for B channel LAPB. Link Access Protocol for D channel LAPD. LAPD is same as HDLC with few modifications. 1. LAPD can be used in either unacknowledged (without sequence numbering) or acknowledged (with sequence numbering) formats. 2. Addressing: 2 bytes address field in LAPD… Prof. Yeshudas Muttu

188. DATA LINK LAYER LAPD – 2 bytes long C/R – Whether command (“0”) or response(“1”) frame. 8th bit “0” indicates continuation to next frame. SAPI – Service access point identifier. Identifies type of upper layer service using a frame. 6 – bit field & therefore define up to 64 different service access points. Prof. Yeshudas Muttu

189. Only 4 of the bit combinations have been assigned 000000- call control for network layer (signalling used of D – channel) 000001 – call control for upper layer (end to end signalling) 010000 – Packet communication (Data use of D – channel) 111111 - Management TEI Field: Unique address of TE Consists of 7 bits & identify up to 128 different TEs Prof. Yeshudas Muttu

190. After connection establishment by D channel, B channel sends data using circuit switching, X.25, or other similar protocols. Network layer functions of D channel defined by ITU-T Q.931. Network layer packet, called message, is encapsulated in information field of a LAPD I-frame for transport across link. Various fields are.. Prof. Yeshudas Muttu NETWORK LAYER

191. Network Layer Packet Format Single 1 byte field – Message type Protocol Discriminator identifies protocol in use— 00001000 for Q.931. 2 or 3 bytes field Call Reference as—- Prof. Yeshudas Muttu

192. Call Reference Field Call reference is sequence number of the call. Length – Length of the remainder of sub field. BRI – 8 bits and PRI – 16 bits. Prof. Yeshudas Muttu

193. Call Reference Value Field Call reference value – number assigned to the call. This number should be quoted while future operation on this call. Number is assigned by TE1 if requesting connection OR assigned by NT if incoming call. First bit is called Flag. Flag – 0 – Message from the originator. Flag – 1 – Message To the originator. Flag needed in case both NT and TE1 allot same number. Call reference value is local between NT and TE1 at each end. Prof. Yeshudas Muttu

194. Message Type Field Message Type – Define application they support and functions they perform. 4 types : Call establishment, Call information, Call clearing messages and miscellaneous messages . Defines Circuit mode connection control, Packet mode, connection control etc. Prof. Yeshudas Muttu

195. Call Establishment Messages Setup: Sent by calling user to network or by network to called user to initiate a call. Setup Acknowledgement: Sent by called user to network or by network to calling user to initiate a indicate— setup received. Connect: Sent by called user to network or by network to calling user to indicate acceptance of the call. Connect Acknowledgement: Sent by network to called user to say that desired connection has been achieved.. Progress: Sent by network to called user to indicate that call establishment is in progress. “Please standby” if needs more time. Alerting: Sent by called user to network or by network to calling user to indicate that call user alert (ringing) has been alerted. Call Processing: Sent by called user to network or by network to calling user to indicate that requested Call Establishment has been initiated. Prof. Yeshudas Muttu

196. Call Information Messages Resume: Sent by a user to the network to request resumption of a suspended call. Resume Acknowledgement: Sent by network the user to acknowledge a request to resume the call. Suspend: Sent by a user to request that the network suspends a call. Suspend Acknowledgement: Sent by the network to the user to acknowledge the requested suspension of the call. Suspend Reject: Sent by the network to the a user to reject the requested suspension. User Information: Sent by the user to the network to be delivered to the remote user. Allows user information sending using out-of band signalling. Prof. Yeshudas Muttu

197. Call Clearing Messages Disconnect: Sent by the calling user to network or by network to the called user to clear end-to-end connection. Release: Sent by user or network to indicate the intention to disconnect and release the channel. Release Complete: Sent by a user or network to show that the channel has been released. Miscellaneous: Protocol specific. Not used in routine communication. Prof. Yeshudas Muttu

198. Information Elements Information elements – Used in setup message to request a bearer service. Contains specific details about required connection. Address of sender and receiver. Routing information. Type of network desired for B channel exchange. Circuit switched, X.25, ATM or frame relay. Contains specific details about the choice of bearer service. Eg . Unrestricted digital information. Contains information about terminal or intended call. Eg .- Destination terminal capability or possibility of inter- networking with other N/W. Prof. Yeshudas Muttu

199. Information Element Types Prof. Yeshudas Muttu

200. Information Element consists of one or more byte. One byte information element can be : Type 1: 1st bit ‘0’, next 3 bits identify information being sent. Remaining 4 bits carry the specific content or attribute of the element. Type 2: 1st bit ‘1’, Next reserved for ID. Information Element Types Prof. Yeshudas Muttu

201. Variable Length: 1st bit of 1st Byte is ‘0’, next 7 bits ID. Second byte defines length of content in bytes. Remaining bytes are content. Information Element Types Prof. Yeshudas Muttu

202. Addressing in ISDN Address Field Description Country Code destination country code of ISDN Number National Destination Code If more than one ISDN service providers serve the subscriber within a single country, this two digit field identifies one of them uniquely Subscriber Number Identifies subscribers ISDN number. Contains 3 digit area code & 7 digit ISDN phone number Sub – Address Additional information Prof. Yeshudas Muttu

203. ISDN Addressing - Example 453 – 716 – 8919 – 788 Number dialled by ISDN subscriber to make a call within the country on same ISDN Network. There is no need for country code & NDC Hence 1 st 10 digits simply identify the called person’s subscriber number. The last 3 digits represent the extension number of the called person (Sub – address) Prof. Yeshudas Muttu

204. Broadband ISDN Data rates originally 64 Kbps – 1.544 Mbps Original BW was narrow Could not support many applications For this B – ISDN was introduced. Provides data rates in range of 600 Mbps  400 times faster than PRI rate. Change from Metallic cables to OFC Prof. Yeshudas Muttu

205. Services Provided by B - ISDN Two types : Interactive & Distributive Interactive: Two way exchange between either 2 subscribers or between a subscriber & a service provider. 3 types: Conversational Telephone calls that support real time services can be used for telephony, video conferencing, data transfer. Prof. Yeshudas Muttu

206. Messaging They are store & forward exchanges All parties in the exchange can use the services at the same time These services include voice mail, data mail, video mail. One subscriber asking another for information may have to wait for an answer even though both parties are available at the same time. i.e. actual exchange may not occur in real time. Prof. Yeshudas Muttu

207. Retrieval Used to retrieve information from a central source called information center. These services are like libraries, they must allow public access & allow the users to retrieve information on demand. Bidirectional service eg : Selecting a video data from an online library. Prof. Yeshudas Muttu

208. Distributive Services Unidirectional services sent from a provider to subscribers without the subscribers having to transmit a request each time a service is desired. They are of two types: Without User Control With User Control Prof. Yeshudas Muttu

209. Without User Control They broadcast to users without the users request. Users Choice is limited whether to receive the service or not. Eg : Commercial TV – Broadcast time & contents are decided by provider alone. Cannot decide the own broadcast time. Prof. Yeshudas Muttu

210. With User Control Broadcast to user in round robin fashion. Services are repeated periodically to allow the user a choice of which time to receive at which services are to be broadcast at which time is providers choice only. Eg : Pay TV  here program is made available in limited time slot. A user wishing to view the program must activate the television to receive it but he/she has no other control. Prof. Yeshudas Muttu

211. Physical Specification for B - ISDN Not related to ATM Provides 3 levels of user needs by 3 access methods: 155.52 Mbps full duplex 155.52 Mbps output/ 622.08 Mbps input 622.08 Mbps full duplex Prof. Yeshudas Muttu

212. 155.520 Mbps Full duplex It is high enough to support customers who need access to all N – ISDN services & one or more regular video transmission services. It caters the need of most residential & many business subscribers. Prof. Yeshudas Muttu

213. 155.520 Mbps output/622.080 Mbps input It provides asymmetrical full – duplex network access Outgoing rate is 155.520 Mbps but, incoming rate is 622.080 Mbps. It is designed to fill the needs of businesses that require the simultaneous reception of multiple services & video conferencing but that are not service providers & do not broadcast distributive services Input needs of such subscribers are much more than their output needs. If only one rate is provided, it may either limit their reception of services or wastage of the link. Asymmetrical configuration provides balanced use of resources. Prof. Yeshudas Muttu

214. 622.080 Mbps Full duplex This is designed for businesses that provide & receive distributive services Functional Grouping These are same as those of N – ISDN. Here they are called B – NT1, B – NT2, B – TE1, B – TE2 & B – TA.   Reference Points B – ISDN also uses the same reference points as N – ISDN (R, S, T, U). Some of these, however are currently under scrutiny & may be redefined. Prof. Yeshudas Muttu

215. Bit Rates for Different Applications Prof. Yeshudas Muttu

216. References https:// gfycat.com/gifs/search/computer+network https:// www.networkacademy.io/ccna/ethernet/type-of-lans https://teachcomputerscience.com/computer-networks / https://blog.packet-foo.com/2016/10/the-network-capture-playbook-part-1-ethernet-basics / https:// www.lifewire.com/layers-of-the-osi-model-illustrated-818017 https://realpars.com/osi / http:// loveocampo.blogspot.com/2018/11/types-of-computer-network.html https://lightwirebusiness.com/wan/