TDC /502, Summer II Unit 1: Introduction. Layering  What is a (communications) network? An interconnected structure that allows attached devices to communicate with each other  Network Applications  Client/Server Model  Example Applications: WWW etc.  Protocols and Standardizations  Network Classifications  LAN, MAN, WAN etc.  Internetwork  Internetworking devices  The Internet as an example  Brief history  Structure of the Internet  RFC (Request for Comments)  Network Architectures  Protocol v.s. Services  OSI and TCP/IP

TDC /502, Summer II Network Protocols = agreed-upon ways in which computers exchange information  Syntax: structure or format of the data  Semantics: meanings  Timing/Procedrue: when data should be sent and how fast it can be sent. Request Service Provide Service v.s. peer-to-peer model

TDC /502, Summer II MAN LAN WAN

TDC /502, Summer II Internetwork Internetworking devices: bridges, routers, brouters, gateways Figure 1-4 The Internet

TDC /502, Summer II The Internet: A collection of networks and routers that span many countries and uses the TCP/IP protocols to form a single, cooperative virtual network. Intranet: connection of different LANs within an organization. Main players in the Internet: Started by U.S. research/military organizations: (D)ARPA: (Defense) Advanced Research Projects Agency  funds technology with military usefulness DoD: U.S. Department of Defense  early adaptor of Internet technology NSF: National Science Foundations  funds university research

TDC /502, Summer II Today: National backbone providers (NBPs) interconnected through exchange points: NAPs (Network Access Points) and MAEs (Metropolitan Area Exchanges) Regional ISPs connects to the NBPs

TDC /502, Summer II Brief History of the Internet 1830: telegraph 1876: telephone (circuit-switching) Development of Early Packet Switching Principles: early 1960's concept of packet switching (Paul Baran) 1965: MIT's Lincoln Laboratory commissions Thomas Marill to study computer networking 1968: ARPAnet contract awarded to Bolt Beranek and Newman (BBN) 1969: ARPAnet has 4 nodes (UCLA, SRI, UCSB, U. Utah), connected by IMPs (Interface message processors); connected by 50 kbps lines 1971: 15 nodes and 23 hosts

TDC /502, Summer II Internetworking, and New and Proprietary Networks 1973: TCP/IP design. First satellite link from California to Hawaii First international connections to the ARPANET:England and Norway 1979: ARPAnet had about 100 nodes 1980s: DARPA funded Berkeley Unix, with TCP/IP : BITNET (IBM protocols) and CSNET (NSF-funded) Early 1980's: split ARPnet (research), MILNET (Military) Proliferation of Networks: 1984: Domain Name Services (Mapping Domain names into IP addresses) 1986: NSFNET created (56kbps backbone) 1989: Internet passes 100,000 nodes First proposal for World Wide Web NSFNET backbone upgraded to T1 (1.544 Mbps)

TDC /502, Summer II Commercialization and the Web: 1990: Original ARPAnet disbanded Fall 1991: CSNET discontinued 1991: Gopher released by University of Minnesota 1992: NSFNET backbone upgraded to T3 ( Mbps) March 1992: First MBONE (Multicast Backbone) video multicast November 1992: First MBONE video multicast Februray 1993: 1,776,000 hosts May 1993: NSF solicited for bids and designated a series of NAPs (e.g. Chicago NAP is run by Ameritech) April 30, 1995: NSFNet backbone disbanded (See for excellent information and links about the architecture of the Internet)

TDC /502, Summer II Some Internet-related organizations ISOC: The Internet SOCiety (ISOC) is a professional membership society with more than 150 organizational and 6,000 individual members in over 100 countries. It provides leadership in addressing issues that confront the future of the Internet, and is the organization home for the groups responsible for Internet infrastructure standards, including the Internet Engineering Task Force (IETF) and the Internet Architecture Board (IAB). IAB: The IAB (Internet Architecture Board) is the Internet Society overseer of the technical evolution of the Internet. The IAB supervises the Internet Engineering Task Force (IETF), which oversees the evolution of TCP/IP, and the Internet Research Task Force (IRTF), which works on network technology.IRTF IETF: The Internet Engineering Task Force (IETF) is a large open international community of network designers, operators, vendors, and researchers concerned with the evolution of the Internet architecture and the smooth operation of the Internet. It is open to any interested individual. Responsible for RFCs (Request for Comments, Internet Standards/drafts) which can be located at ICANN: The Internet Corporation for Assigned Names and Numbers (ICANN) is the non-profit corporation that was formed to assume responsibility for the IP address space allocation, protocol parameter assignment, domain name system management, and root server system management function previously performed under U.S. Government contract by IANA (Internet Assigned Numbers Authority) and other entities.Internet Assigned Numbers Authority --

TDC /502, Summer II Figure 1-1 Maturity levels of an RFC

TDC /502, Summer II Analogy: Application = boss Transport = secretary Network Access = post office

TDC /502, Summer II ISO OSI Model (ISO = International Standard Organization, OSI = Open Systems Interconnection) Bits Frames Packets Error and Flow Control over a single link End-to-end Error and Flow Control Also data compression and encryption Synchronization – mechanism for inserting check points Dialog control – half- duplex or full-duplex

TDC /502, Summer II Figure 2-2 OSI Layers

TDC /502, Summer II Figure 2-3 An exchange using the OSI model Layer 5 PDU (Protocol Data Unit) = Layer 6 PDU + Layer 5 header Virtual communication between layer 5 entities (software implementation ) Encapsulation Decapsulation

TDC /502, Summer II Figure 2-7 Transport Layer

TDC /502, Summer II Figure 2-8 Session Layer

TDC /502, Summer II Figure 2-10 Application Layer Directory Service File transfer and management

TDC /502, Summer II Service: What is provided? Protocol: How is the service provided? Layer N+1 entity Layer N entity Interface. Passing Service Primitives (e.g. request and parameters) Exchange Layer N PDUs

TDC /502, Summer II Services A connection is set up first Full addresses needed to set up. May use connection number for exchanging data and connection release Data delivered in sequence. Full addresses with all data units Data may be delivered out of sequence.

TDC /502, Summer II = connection.request 2.= connection.indication 3.= connection.response 4.= connection.confirm 5.= data.request 6.= data.indication 7.= disconnection.request 8.= disconnection.indication

TDC /502, Summer II Figure 2-11 TCP/IP and OSI Model Connection-oriented Connectionless

TDC /502, Summer II Figure 2-13 Relationship of layers and addresses in TCP/IP Example: web browser implementing HTTP Implemented in TCP and UDP software. HTTP uses TCP. Interface. Eg. WINSOCK on PCs Implemented in IP software Eg. Ethernet Medium Access Control (MAC) implemented in NIC card (Network Interface Card) and driver software Eg. Ethernet PHY layer. Implemented in NIC card Eg. TCP port 80 for web server Eg (32- bit) Eg. Ethernet address (48-bit)

TDC /502, Summer II Figure 2-14 Physical addresses: identify and interface card (Link address, MAC address) Usually contains a checksum/Frame check sequence for detecting errors. Calculated based on the rest of the frame. CRC (Cyclic redundancy check) is commonly used.

TDC /502, Summer II Figure 2-15 IP addresses (A logical address necessary for universal communication over the internet, and is independent of the underlying physical networks) Note: We commonly uses names such as (called Domain Names). To translate from names to IP addresses, needs to use DNS (Domain Name Service) implemented at the Application level.

TDC /502, Summer II Figure 2-16 Port addresses (Different processes communicate through different ports)