Who is Who in the Internet ?

Who is Who in the Internet ? • Internet Engineering Task Force (IETF):The IETF is the protocol engineering and development arm of the Internet. Subdivided into many working groups, which specify Request For Comments or RFCs. (www.ietf.org) • IRTF (Internet Research Task Force):The Internet Research Task Force is a composed of a number of focused, long-term and small Research Groups. • E.g., Anti-spam group, delay tolerant networking group, Network management group, Routing research group, Peer-to-peer research group (www.irtf.org) • Internet Architecture Board (IAB) • The Internet Engineering Steering Group (IESG)

Internet Standardization Process • All standards of the Internet are published as RFC (Request for Comments). • A typical way of standardization is: • Internet Drafts • RFC • Proposed Standard • Draft Standard (requires 2 working implementation) • Internet Standard (declared by IAB) • Consensus based standardization

At The Not So Very Beginning

Necessity • Proliferation of Computers in Public and Business Utilities • Availability of Data Based Services (no pun intended) • End User Growth • Communication Technology Evolved • Research and Commercial Motives

Sample Applications • Remote Access to Resources • E.g., Telnet • Shared access to data/files • FTP, NFS, AFS • Remote Computer Aided Learning • Online audio/video lectures, web casting, demos • Remote Data Operations and Computation • E.g., Airline reservation systems, inventory control systems • Other applications like, e-mail, ftp, http, p2p, instant messaging, news groups etc • Now: IP-* (Telephony, TV, Radio, Movies, Music etc)

Network Classification Parameters • Latency • Bandwidth • Loss rate • Number of end systems • Service interface (how to invoke?) • Other details • Reliability • Communication capability: unicast, multicast, broadcast • Applicability: E.g., Real-time (e.g., postal service?) • Switching technology: message vs. packet

Network Classification Parameters... • Communication Medium: Electrons and photons • Links: Optical fiber, copper, satellite, etc • Switches: Electronic/optical, crossbar/Banyan • Protocols: TCP/IP, ATM, MPLS, SONET, Ethernet, PPP, X.25, FrameRelay, AppleTalk, IPX, SNA • Functionalities: Routing, error control, congestion control, Quality of Service (QoS) • Applications: FTP, WEB, X windows, SSH

Types of Computer Networks • Geographical distance • Local Area Networks (LAN): Ethernet, Token ring, FDDI • Metropolitan Area Networks (MAN): DQDB and later, SMDS • Wide Area Networks (WAN): X.25, ATM, frame relay • Information type • Data networks vs. telecommunication networks • Application type • Special purpose networks: airline reservation network, banking network, credit card network, telephony • General purpose network: Internet

Types of Computer Networks • Right to use • private: enterprise networks • public: telephony network, Internet • Ownership of protocols • proprietary: SNA, DNA • open: IP • Technologies • terrestrial vs. satellite • wired vs. wireless • Protocols • IP, AppleTalk, SNA

Definition of Computer Network • A computer network is an interconnected collection of autonomous computers. • Two computer are interconnected if they are able to exchange information • Two computer are autonomous if they are capable of operating independently, that is, neither is capable of forcibly starting, stopping, or controlling the other • Network users (not necessarily application users) are aware of the network existence Autonomous

Just to be clear –What are not Computer Networks • Master/slave systems (ref. any centralized cluster) • Single-host networks (E.g., UNIX) • Multi-computers, such as the hypercube (ref. parallel computing) • In terms of (operating) systems, there is some distinction between network systems and distributed systems • Distributed system gives the view of a single computer to the user (user not aware of networking behind scenes) • Failure of any node in the system might stop other nodes from operating correctly (non-autonomous) • Focus is on software, distributed computation, that can do better resource sharing, concurrent processing etc • Important problems: load balancing, fault-tolerance, mutual exclusion

Now That We are Clear • How to build a computer network? • Agree upon the communication technique (circuit switching or store-and-forward switching) • Develop communication languages for hosts to interact (protocols) • Implement appropriate functionality without affecting the computer’s performance (designing the protocol stack) • Develop network-centric algorithms (routing, reliability, congestion control)

Types of Communication Networks • Exchange mechanism Communication Network SwitchedCommunication Network BroadcastCommunication Network Packet-SwitchedCommunication Network Circuit-SwitchedCommunication Network Virtual Circuit Network Datagram Network

Broadcast vs. Switched Communication Networks • Broadcast communication networks • information transmitted by any node is received by every other node in the network in range • E.g.,: usually in LANs (Ethernet, Wireless) , Radio • Problem: coordinate the access of all nodes to the shared communication medium (Multiple Access Problem) • Switched communication networks • information is transmitted to a sub-set of designated nodes • Examples: WANs (Telephony Network, Internet), ATM • Problem: how to forward information to intended node(s) • This is done by special nodes (E.g., bridges, routers, switches) running routing protocols

A Taxonomy of Communication Networks Communication Network SwitchedCommunication Network BroadcastCommunication Network Packet-SwitchedCommunication Network Circuit-SwitchedCommunication Network Virtual Circuit Network Datagram Network

Circuit Switching • Three phases • circuit establishment • data transfer • circuit termination • If circuit not available: “Busy signal” • Examples • Telephone networks • ISDN (Integrated Services Digital Networks)

Circuit Establishment Data Transmission Circuit Termination Timing in Circuit Switching Host 1 Host 2 Node 1 Node 2 DATA processing delay at Node 1 propagation delay between Host 1 and Node 1 propagation delay between Host 2 and Node 1

Circuit Switching • A node (switch) in a circuit switching network Node incoming links outgoing links

Circuit Switching: Multiplexing/Demultiplexing • Time divided in frames and frames divided in slots • Relative slot position inside a frame determines which conversation the data belongs to • Needs synchronization between sender and receiver • In case of non-permanent conversations • Needs to dynamic bind a slot to a conservation • How to do this?

Packet Switching • Data are sent as formatted bit-sequences, so-called packets. • Packets have the following structure: • Header and Trailer carry control information (e.g., destination address, check sum) • Each packet is passed through the network from node to node along some path (Routing) • At each node the entire packet is received, stored briefly, and then forwarded to the next node (Store-and-Forward Networks) • Typically no capacity is allocated for packets Header Data Trailer

Packet Switching • A node in a packet switching network Node incoming links outgoing links Memory

Packet Switching: Multiplexing/Demultiplexing • Data from any conversation can be transmitted at any given time • How to tell them apart? • use meta-data (header) to describe data

Datagram Packet Switching • Each packet is independently switched • Each packet header contains destination address • No resources are pre-allocated (reserved) in advance • Example: IP networks

Packet 1 Packet 1 Packet 1 Packet 2 Packet 2 Packet 2 Packet 3 Packet 3 Packet 3 Timing of Datagram Packet Switching Host 1 Host 2 Node 1 Node 2 propagation delay between Host 1 and Node 2 transmission time of Packet 1 at Host 1 processing delay of Packet 1 at Node 2

Datagram Packet Switching Host C Host D Host A Node 1 Node 2 Node 3 Node 5 Host B Host E Node 7 Node 6 Node 4

Virtual-Circuit Packet Switching • Hybrid of circuit switching and packet switching • data is transmitted as packets • all packets from one packet stream are sent along a pre-established path (=virtual circuit) • Guarantees in-sequence delivery of packets • However: Packets from different virtual circuits may be interleaved • Example: ATM networks

Virtual-Circuit Packet Switching • Communication with virtual circuits takes place in three phases • VC establishment • data transfer • VC disconnect • On demand circuit setup, several packets may share same virtual link

Packet-Switching vs. Circuit-Switching • Most important advantage of packet-switching over circuit switching: Ability to exploit statistical multiplexing: • efficient bandwidth usage; ratio between peek and average rate is 3:1 for audio, and 15:1 for data traffic • However, packet-switching needs to deal with congestion: • more complex routers • harder to provide good network services (e.g., delay and bandwidth guarantees) • In practice they are combined: • IP over SONET, IP over Frame Relay

Who is Who in the Internet ?