![Protocols
● Definition: A protocol defines the format and the order of messages exchanged between
two or more communicating entities, as well as the actions taken on the transmission and/or
receipt of a message or other event.
● Transmission Control Protocol (TCP): The Internet’s principal protocols
● Internet Protocol (IP): specifies the format of the packets that are sent and received
among routers and end systems
● Internet standards are developed by the Internet Engineering Task Force (IETF)
● The IETF standards documents are called requests for comments (RFCs)
● RFCs tend to be quite technical and detailed. They define protocols such as TCP, IP, HTTP
(for the Web), and SMTP (for e-mail). There are currently nearly 9000 RFCs.
● for network links.
● The IEEE 802 LAN Standards Committee [IEEE 802 2020], for example, specifies the
Ethernet and wireless WiFi standards.](https://image.slidesharecdn.com/internet-introduction-210827050521/85/Internet-introduction-6-320.jpg)
Internet introduction
- 1. INTERNET - Introduction M.M. Sajith Graduate Electrical and Electronics Engineering mmssajith@gmail.com
- 2. Internet Explanation is categorized into 2: 1. Basic h/w and s/w components 2. Networking infrastructure
- 3. Basic H/W and S/W ● End user is called Host ● End systems are connected together by a network of communication links and packet switches. ● Transmission rate of a link measured in bits/second ● Data are sent in Packets ● A packet switch takes a packet arriving on one of its incoming communication ● links and forwards that packet on one of its outgoing communication links. ○ Routers: in network core ○ Link-Layer Switches: Used in access network ● Route/Path: The sequence of communication links and packet switches traversed by a packet from the sending end system to the receiving end system ● Packet-switched networks/ Circuit Switched Network ● Internet Service Providers (ISPs)
- 4. Internet ● Definition: an infrastructure that provides services to applications ● Distributed applications: Internet applications run on end systems—they do not run in the packet switches in the network core. Although packet switches facilitate the exchange of data among end systems, they are not concerned with the application ● Socket interface: Specifies how a program running on one end system asks the Internet infrastructure to deliver data to a specific destination program running on another end system. ● Hardware level Definition: Connection between multiple devices.
- 5. Protocols ● A protocol defines the format and the order of messages exchanged between two or more communicating entities, as well as the actions taken on the transmission and/or receipt of a message or other event. ● All activity in the Internet that involves two or more communicating remote entities is governed by a protocol ● Hardware-implemented protocols in two physically connected computers control the flow of bits on the “wire” between the two network interface cards ● Congestion-control protocols in end systems control the rate at which packets are transmitted between sender and receiver ● Protocols in routers determine a packet’s path from source to destination
- 6. Protocols ● Definition: A protocol defines the format and the order of messages exchanged between two or more communicating entities, as well as the actions taken on the transmission and/or receipt of a message or other event. ● Transmission Control Protocol (TCP): The Internet’s principal protocols ● Internet Protocol (IP): specifies the format of the packets that are sent and received among routers and end systems ● Internet standards are developed by the Internet Engineering Task Force (IETF) ● The IETF standards documents are called requests for comments (RFCs) ● RFCs tend to be quite technical and detailed. They define protocols such as TCP, IP, HTTP (for the Web), and SMTP (for e-mail). There are currently nearly 9000 RFCs. ● for network links. ● The IEEE 802 LAN Standards Committee [IEEE 802 2020], for example, specifies the Ethernet and wireless WiFi standards.
- 7. Network Edge ● End systems of Internet are called network Edge. (Server, PC, Mobile Phones) ● End systems = Hosts (They host(run) the web browser program, web server program, e-mail client program, e-mail server program) ● Hosts are catogarized as ○ Server: powerful machines that store and distribute Web pages, stream video, relay e-mail, and so on. Severs resides in Data Centers ○ Client: desktops, laptops, smartphones
- 8. Access N/W ● The network that physically connects an end system to the first router (also known as the “edge router”) on a path from the end system to any other distant end system.
- 9. Home Access Network ● DSL (Digital Subscriber Line), Cable are used in Home Access Networks mostly. DSL is obtained from Local phone company that provides wired local phone access. They act as an ISP for their customers. ● Splitters: separates the data and telephone signals arriving to the home and forwards the data signal to the DSL modem ● In the Telephone Company side DSLAM do the work of Splitter. ● Downstream (24 & 52 Mbps)and Upstream (3.5 & 16 Mbps) rates (speeds are limited by: ○ The package chosen by customer/ Payment ○ Distance between the home and Company (5-10 miles is okay to receive internet) ○ Gauge of twisted pair line ○ Degree of Electric Interference Digital Signal Analog Signal ● DSLAM - Digital Subscriber Line Access Multiplexer ● Modem - Modulator Demodulator
- 10. ● Cable Internet access uses television company’s existing lines. ● Cable internet access requires cable modems which is an external device and connects to the home PC through an Ethernet port. ● Cable modem Divide HFC into 2 ○ Downstream 40Mbps/ 1.2 Gbps ○ Upstream 30 Mbps/100Mbps ● DOCSIS- International standards to add high bandwidth data to an existing Cable TV system. CMTS - Cable Modem Termination System HFC - Hybrid Fibre Optics DOCSIS- Data Over Cable Service Interface Specification
- 11. ● FTTH: Divided into 2 ○ Active Optical Network (AON) ○ Passive Optical Network (PON) ● OLT, providing conversion between optical and electrical signals ● 5G Wireless Networks OLT: Optical Line Terminal ONT: Optical Network Terminal PON
- 12. Access in the Enterprise ● Ethernet users use twisted-pair copper wire to connect to an Ethernet switch ● users typically have 100 Mbps to tens of Gbps access to the Ethernet switch, whereas servers may have 1 Gbps 10 Gbps access. ● For Wireless network users get WiFi (IEEE 802.11 standard) (100Mbps) from an Access Point. Eg. Wireless WAN - 3G,LTE 4G,5G LTE - Long Term Evolution 3G - 3rd Generation
- 13. Physical Media ● Each bit travel between receiver and sender need to pass several transmitters and receivers. ● For each transmitter-receiver pair, the bit is sent by propagating electromagnetic waves or optical pulses across a physical medium. ● Eg for Physical Media. twisted-pair copper wire, coaxial cable, multimode fiber-optic cable, terrestrial radio spectrum, and satellite radio spectrum. ● 2 types ○ Guided Media (the waves are guided along a solid medium, Eg. fiber-optic cable, a twisted-pair copper wire, or a coaxial cable) ○ Unguided Media (the waves propagate in the atmosphere and in outer space)
- 14. Twisted-Pair Copper Wire ● The wires are twisted together to reduce the electrical interference from similar pairs close by ● 2 Types ○ Shielded Twisted Pair ○ Unshielded Twisted Pair (Used in LANs 10Mbps to 10Gbps) ● Data rates depend on ○ Thickness of the wire ○ Distance between Tx and Rx
- 15. Coaxial Cable ● coaxial cable consists of two copper conductors ● Use in cable TV system ● Data rate - 100Mbps ● Coaxial cable can be used as a guided shared medium. Specifically, a number of end systems can be connected directly to the cable, with each of the end systems receiving whatever is sent by the other end systems.
- 16. Fiber Optics ● a thin, flexible medium that conducts pulses of light, with each pulse representing a bit ● They are immune to electromagnetic interference, have very low signal attenuation up to 100 kilometers, and are very hard to tap ● Good for Long Haul because of speed ● Not suitable for short haul because of cost
- 17. Terrestrial Radio Channels ● Carry signals in the electromagnetic spectrum ● They require no physical wire to be installed, can penetrate walls, provide connectivity to a mobile user, and can potentially carry a signal for long distances ● Depends on ○ Propagation environment ■ Path loss ■ Shadow fading ■ Multipath fading ■ interference ○ Distance ● 3 groups ○ operate over very short distance (wireless headsets, keyboards, and medical devices) ○ operate in local areas (100m) (local-area radio channels) ○ Operate in the wide area (10km) (cellular access technologies)
- 18. Satellite Radio Channels ● A communication satellite links two or more Earth-based microwave transmitter/receivers, known as ground stations. ● 2 types are used in communication: ○ geostationary satellites(GEO): permanently remain above the same spot on Earth. placing the satellite in orbit at 36,000 kilometers above Earth’s surface. This distance create a delay of 280ms ○ low-earth orbiting (LEO) satellites: placed much closer to Earth and do not remain permanently above one spot on Earth They rotate around Earth and may communicate with each other, as well as with ground stations.
- 19. Network Core - Packet Switching ● There are two fundamental approaches to moving data through a network of links and switches: ○ circuit switching ○ packet switching. ● Store and Forward transmission in each Packet switches (Routers and link layer switches) ● Queuing Delays and Packet Loss: ○ Packet switch has an Output buffer (Output Queue) for each attached link ○ If the link the packet to be transmitted is busy then it will wait in the output buffer ○ Here Queuing delay will occur ○ If the buffer is full the receiving packet or one of the already stored packet will be dropped. Packet Loss ● Forwarding Table and Routing Protocol
- 20. Pros and Cons of Packet Switching + works well for transferring data that does not require constant transfer rate + provides better network resource sharing + No reservation - opportunities for accumulation, which in turn leads to losses and delays (no time guarantees) - thus there is a need for protocols that provide reliable transfer - no bandwidth guarantees - because of.accumulation and packet loss
- 21. Network Core - Circuit Switching ● The resources needed along a path (buffers, link transmission rate) to provide for communication between the end systems are reserved for the duration of the communication session between the end systems. But in packet switching there is no reserved path for communication ○ Earlier telephone networks. Each Sender to receiver line is called as circuit.
- 22. Multiplexing in Circuit-Switched Networks ● circuit in a link is implemented with either ○ frequency-division multiplexing (FDM): ■ the frequency spectrum of a link is divided up among the connections established across the link. Specifically, the link dedicates a frequency band to each connection for the duration of the connection. The width of the band is called bandwidth. ○ time-division multiplexing (TDM). ■ Time is divided into frames of fixed duration, and each frame is divided into a fixed number of time slots. When the network establishes a connection across a link, the network dedicates one time slot in every frame to this connection. These slots are dedicated for the sole use of that connection, with one time slot available for use (in every frame) to transmit the connection’s data. ● In circuit switching, the dedicated circuits are idle during silent periods.
- 23. Packet Switching vs Circuit Switching Packet Switching Circuit Switching Transferring data that does not require constant transfer rate Has constant transfer rate simpler, more efficient, and less costly to implement Complex system (Routing Algorithm and Forwarding Table) and more cost not suitable for real-time services because of its variable and unpredictable end-to-end delays Suitable for real time sharing No bandwidth guarantee Dedicated circuit is allocated for each data transfer
- 24. Types of Delays inside Network ● Nodal processing delay ● Queuing delay ● Transmission delay ● Propagation delay
- 25. Transmission Delay ● End systems exchange messages with each other ● To send a message from a source end system to a destination end system, the source breaks long messages into smaller chunks of data known as packets. Packet travels through communication links and packet switches. ● Transmission Delay: This is the amount of time required to push (that is, transmit) all of the packet’s bits into the link. ● L bits size packet is sent with R bits/second rate. ● first-come-first-served manner ● For single link Transmission time = L/R ● Most packet switches use store and forward transmission method. Store-and-forward transmission means that the packet switch must receive the entire packet before it can begin to transmit the first bit of the packet onto the outbound link. ● For N number of links Transmission time = NL/R
- 26. Propagation Delay ● Once a bit is pushed into the link, it needs to propagate to router B. The time required to propagate from the beginning of the link to router B is the propagation delay ● Propagation delay depends on Medium of propagation. ● Propagation Delay = d/s ○ d = Distance ○ s = Speed
- 27. Processing Delay ● The time required to examine the packet’s header and determine where to direct the packet is part of the processing delay. Queuing Delay ● At the queue, the packet experiences a queuing delay ● Depends on number of packets before a packet dnodal = dproc + dqueue + dtrans + dprop
- 28. Protocol Layering ● Network protocol defines ○ The format of messages being exchanged ○ The order of messages exchanged between the nodes ○ Which actions are initiated upon receipt and sending messages ● To provide structure to the design of network protocols, network designers organize protocols—and the network hardware and software that implement the protocols— in layers. ● each layer provides its service by ○ performing certain actions within that layer and by ○ using the services of the layer directly below it ● A protocol layer can be implemented in software, in hardware, or in a combination of the two. ● Advantage: ○ Easy to identify functionality ○ Easy to discuss problem area using common reference model ○ Easy to maintain (Changes to the implementation in a team will be transparent for the rest of the system) ● Disadvantage: ○ one layer may duplicate lower-layer functionality ● The protocols of the various layers are called the protocol stack.
- 29. ● Challenges faced before introducing the layered protocol ○ Representation of digital data ○ Data rate (bits per second - bps) ○ Shared or dedicated media ○ Routing through the network ○ Addressing ○ Error detection ● Reference models: ○ ISO's OSI model ○ TCP / IP model
- 30. OSI Model ● Developed by ISO (International Standards Organization) ● OSI model describes what each team should do ○ each team is based on services in the underlying team and offers services to the team above ○ ISO has also produced protocols for each team ● Implementations of the OSI model were never some success, due ○ poor implementations, due to over organization i.e. for many layers ○ origin from the telecom industry - not well received inside the IT world ○ TCP / IP was already in use when the OSI model arrived
- 31. TCP/IP (Transmission Control Protocol/ Internet Protocol) Model ● The model consists of 5 layers and is actually one simplified OSI model ● Each team has different protocols defined in various RFCs administered by the IETF ● Basis for today's Internet
- 32. Application Layer ● HTTP (which provides for Web document request and transfer) ● SMTP (which provides for the transfer of e-mail messages) ● FTP (which provides for the transfer of files between two end systems) ● Domain Name System (DNS)
- 33. Transport Layer ● The Internet’s transport layer transports application-layer messages between application endpoints. 2 types: ○ UDP:provides a connectionless service to its applications. This is a no-frills service that provides no reliability, no flow control, and no congestion control. ○ TCP: provides a connection- oriented service to its applications. This service includes guaranteed delivery of application-layer messages to the destination and flow control (that is, sender/receiver speed matching).TCP also breaks long messages into shorter segments and provides a congestion-control mechanism, so that a source throttles its transmission rate when the network is congested. ○
- 34. Network Layer ● network layer is responsible for moving network-layer packets known as datagrams from one host to another ● The Internet transport-layer protocol (TCP or UDP) in a source host passes a transport-layer segment and a destination address to the network layer, The network layer then provides the service of delivering the segment to the transport layer in the destination host. ● This includes ○ Internet Protocol (IP): which defines the fields in the datagram as well as how the end systems and routers act on these fields ○ Routing protocols: determine the routes that datagrams take between sources and destinations ●
- 35. Link Layer ● In the sender side Link layer pass the datagram from Network layer to physical layer. In the receiver side the Link layer get the datagram from Physical layer and pass it to Network layer ○ Eg: Ethernet, WiFi, and the cable access network’s DOCSIS protocol
- 36. Physical Layer ● The physical layer is to move the individual bits within the frame from one node to the next. ○ Eg. twisted-pair copper wire, single-mode fiber optics
- 37. Encapsulation ● At the sending host, an application-layer message (M) is passed to the transport layer. ● the transport layer takes the message and appends additional information (transport-layer header information, Ht) that will be used by the receiver-side transport layer. The application-layer message and the transport-layer header information together constitute the transport-layer segment. ● The transport layer then passes the segment to the network layer, which adds network-layer header information (Hn) such as source and destination end system addresses, creating a network-layer datagram ● The datagram is then passed to the link layer, which will add its own link-layer header information and create a link-layer frame. ● a packet has two types of fields: ○ header fields ○ payload field ●
- 38. History ● 1961: Kleinrock - meat theory shows great efficiency with packet switching ● 1964: Baran - packet switching i military networks ● 1967: ARPAnet started off Advanced Research Projects Agency ● 1969: first operational ARPAnet packet switch (IMP),4 package switches- precursor to today's Internet ● 1972: ○ ARPAnet public demonstrated ○ NCP (Network Control Protocol, RFC-001) first machine-to-machine protocol ○ first email program based at NCP ○ ARPAnet has 15 packet switches (IMPs)
- 39. ● 1972-1980: "Internetworking", new and proprietary networks ● 1970: ALOHAnet package-based radio network in Hawaii ● 1973: R. Metcalfe's doctoral dissertation about Ethernet ● 1974: Vint Cerf and Kahn - architecture for networking ● late 70s: ○ The basis for TCP, UDP and IP laid ○ other architectures: DECnet, SNA m.fl. ○ switching with fixed pack sizes ● 1979: ARPAnet has 200 nodes ● Cerf and Kahn's principles for "internetworking" ● minimalism, autonomy - none internal changes required to networking ● service model based on best- effort ● stateless routers ● decentralized control
- 40. 1980-1990: new protocols ● 1983: TCP / IP is used on ARPAnet ● 1982: SMTP email protocol defined ● 1983: DNS defined for translation between domain names and IP addresses ● 1985: FTP protocol defined ● 1988:TCP accumulation control
- 41. 1990, early 2000: commercialization, introduction of WWW ● The beginning of the 1990s: WWW ○ Hypertext ○ html, http: Tim Berners-Lee ○ 1994: Mosaic, later Netscape ○ 1996: Microsoft "discovers" Internet ○ 1992: ca. 200 operational web-servants ● Late 1990s, 2000: ○ commercialization of WWW ○ Ca. 50 million computers on the Internet ○ Ca. 100 million + users ○ Backbone links at many Gbps ○ new services such as IRC, IM and file sharing (P2P) mm ○ Safety becomes important! ● 2007 ○ ~ 750 million PCs online ○ Extensive development of broadband ○ Voice and video over IP ○ P2P applications: BitTorrent (file sharing) Skype (VoIP),PPLive (video) ○ More applications: YouTube, Facebook, Twitter, online games etc. ○ Wireless networks, mobility ○ Microsoft & Google with their own content provider networks ○ Cloud computing - services in the «cloud»