Review of Important Networking Concepts Introductory material using Prof. Liebeherr on-line notes Review of important networking concepts: protocol architecture, protocol layers, encapsulation, demultiplexing, network abstractions.

Networking Concepts Layered Architecture to reduce complexity Encapsulation Abstractions

Sending a packet from Argon to Neon

Sending a packet from Argon to Neon 128.143.71.21 is not on my local network. Therefore, I need to send the packet to my default gateway with address 128.143.137.1 128.143.71.21 is on my local network. Therefore, I can send the packet directly. DNS: What is the IP address of “neon.netlab.edu”? DNS: The IP address of “neon.netlab.edu” is 128.143.71.21 ARP: What is the MAC address of 128.143.137.1? ARP: The MAC address of 128.143.137.1 is 00:e0:f9:23:a8:20 ARP: What is the MAC address of 128.143.71.21? ARP: The MAC address of 128.143.137.1 is 00:20:af:03:98:28 frame frame

What’s a protocol? human protocols: “what’s the time?” “I have a question” introductions … specific msgs sent … specific actions taken when msgs received, or other events network protocols: machines rather than humans all communication activity in Internet governed by protocols protocols define format, order of msgs sent and received among network entities, and actions taken on msg transmission, receipt

What’s a protocol? Hi Hi 2:00 <file> time a human protocol and a computer network protocol: Hi TCP connection req Hi TCP connection response Got the time? Get http://www.awl.com/kurose-ross 2:00 <file> time Q: Other human protocols?

Communications Architecture The complexity of the communication task is reduced by using multiple protocol layers: Each protocol is implemented independently Each protocol is responsible for a specific subtask Protocols are grouped in a hierarchy A structured set of protocols is called a communications architecture or protocol suite

TCP/IP Protocol Suite The TCP/IP protocol suite is the protocol architecture of the Internet The TCP/IP suite has four layers: Application, Transport, Network, and Data Link Layer End systems (hosts) implement all four layers. Gateways (Routers) only have the bottom two layers.

Functions of the Layers Data Link Layer: Service: Reliable transfer of frames over a link Media Access Control on a LAN Functions: Framing, media access control, error checking Network Layer: Service: Move packets from source host to destination host Functions: Routing, addressing Transport Layer: Service: Delivery of data between hosts Functions: Connection establishment/termination, error control, flow control Application Layer: Service: Application specific (delivery of email, retrieval of HTML documents, reliable transfer of file) Functions: Application specific

TCP/IP Suite and OSI Reference Model The TCP/IP protocol stack does not define the lower layers of a complete protocol stack

Assignment of Protocols to Layers

Layered Communications An entity of a particular layer can only communicate with: 1. a peer layer entity using a common protocol (Peer Protocol) 2. adjacent layers to provide services and to receive services

Service Primitives Communication services are invoked via function calls. The functions are called service primitives N+1 Layer Entity N+1 Layer Peer Protocol N+1 Layer Entity Request Delivery Indicate Delivery N Layer Entity N Layer Entity

Service Primitives Recall: A layer N+1 entity sees the lower layers only as a service provider N+1 Layer Entity N+1 Layer Peer Protocol N+1 Layer Entity Request Delivery Indicate Delivery Service Provider

Layers in the Example

Layers in the Example Send the datagram to 128.143.7.21 Send HTTP Request to neon Establish a connection to 128.143.71.21 at port 80 Open TCP connection to 128.143.71.21 port 80 IP datagram is a TCP segment for port 80 Send a datagram (which contains a connection request) to 128.143.71.21 Send IP data-gram to 128.143.71.21 Send IP datagram to 128.143.71.21 Frame is an IP datagram Frame is an IP datagram Send the datagram to 128.143.137.1 Send the datagram to 128.143.7.21 Send Ethernet frame to 00:e0:f9:23:a8:20 Send Ethernet frame to 00:20:af:03:98:28

Layers and Services Service provided by TCP to HTTP: reliable transmission of byte streams over a logical connection Service provided by IP to TCP: unreliable transmission of IP datagrams across an IP network Service provided by Ethernet to IP: transmission of a frame across an Ethernet segment Other services: DNS: translation between domain names and IP addresses ARP: Translation between IP addresses and MAC addresses

Encapsulation & Demultiplexing As data is moving down the protocol stack, each protocol is adding layer-specific control information

Encapsulation & Demultiplexing in our Example Let us look in detail at the Ethernet frame between Argon and the Router, which contains the TCP connection request to Neon. This is the frame in hexadecimal notation. 00e0 f923 a820 00a0 2471 e444 0800 4500 002c 9d08 4000 8006 8bff 808f 8990 808f 4715 065b 0050 0009 465b 0000 0000 6002 2000 598e 0000 0204 05b4

Encapsulation & Demultiplexing

Encapsulation & Demultiplexing: Ethernet Header

Encapsulation & Demultiplexing: IP Header

Encapsulation & Demultiplexing: IP Header

Encapsulation & Demultiplexing: TCP Header Option: maximum segment size

Encapsulation & Demultiplexing: TCP Header

Encapsulation & Demultiplexing: Application data

Different Views of Networking Different Layers of the protocol stack have a different view of the network. This is HTTP’s and TCP’s view of the network.

Network View of IP Protocol

Network View of Ethernet Ethernet’s view of the network

The Evolution of Internet Introductory material. An overview lecture that covers Internet related topics, including a definition of the Internet, an overview of its history and growth, and standardization and naming.

A Definition On October 24, 1995, the FNC unanimously passed a resolution defining the term Internet. RESOLUTION: The Federal Networking Council (FNC) agrees that the following language reflects our definition of the term "Internet". "Internet" refers to the global information system that -- (i) is logically linked together by a globally unique address space based on the Internet Protocol (IP) or its subsequent extensions/follow-ons; (ii) is able to support communications using the Transmission Control Protocol/Internet Protocol (TCP/IP) suite or its subsequent extensions/follow-ons, and/or other IP-compatible protocols; and (iii) provides, uses or makes accessible, either publicly or privately, high level services layered on the communications and related infrastructure described herein.

Internet History 1961-1972: Early packet-switching principles 1972: 1961: Kleinrock - queueing theory shows effectiveness of packet-switching 1964: Baran - packet-switching in military nets 1967: ARPAnet conceived by Advanced Research Projects Agency 1969: first ARPAnet node operational 1972: ARPAnet demonstrated publicly NCP (Network Control Protocol) first host-host protocol first e-mail program ARPAnet has 15 nodes

Internet History 1972-1980: Internetworking, new and proprietary nets Cerf and Kahn’s internetworking principles: minimalism, autonomy - no internal changes required to interconnect networks best effort service model stateless routers decentralized control define today’s Internet architecture 1970: ALOHAnet satellite network in Hawaii 1973: Metcalfe’s PhD thesis proposes Ethernet 1974: Cerf and Kahn - architecture for interconnecting networks late70’s: proprietary architectures: DECnet, SNA, XNA late 70’s: switching fixed length packets (ATM precursor) 1979: ARPAnet has 200 nodes

Internet History Late 1990’s – 2000’s: 1990, 2000’s: commercialization, the Web, new apps Early 1990’s: ARPAnet decommissioned 1991: NSF lifts restrictions on commercial use of NSFnet (decommissioned, 1995) early 1990s: Web hypertext [Bush 1945, Nelson 1960’s] HTML, HTTP: Berners-Lee 1994: Mosaic, later Netscape late 1990’s: commercialization of the Web Late 1990’s – 2000’s: more killer apps: instant messaging, P2P file sharing network security to forefront est. 50 million host, 100 million+ users backbone links running at Gbps

Applications of the Internet Traditional core applications: Email News Remote Login File Transfer The killer application: World-Wide Web (WWW), P2P Future applications: Videoconferencing and Telephony Multimedia Services Internet Broadcast

Growth of the Internet Source: Internet Software Consortium

Internet Infrastructure

Internet Infrastructure The infrastructure of the Internet consists of a federation of connected networks that are each independently managed (“autonomous system”) Note: Each “autononmous system may consist of multiple IP networks Hierarchy of network service providers Tier-1: nation or worldwide network (US: less than 20) Tier-2: regional networks (in US: less than 100) Tier-3: local Internet service provider (in US: several thousand)

Internet Infrastructure Location where a network (ISP, corporate network, or regional network) gets access to the Internet is called a Point-of-Presence (POP). Locations (Tier-1 or Tier-2) networks are connected for the purpose of exchanging traffic are called peering points. Public peering: Traffic is swapped in a specific location, called Internet exchange points (IXPs) Private peering: Two networks establish a direct link to each other.

Tier-1 ISP: e.g., Sprint Sprint US backbone network

Who is Who on the Internet ? Internet Society (ISOC): Founded in 1992, an international nonprofit professional organization that provides administrative support for the Internet. Founded in 1992, ISOC is the organizational home for the standardization bodies of the Internet. Internet Engineering Task Force (IETF): Forum that coordinates the development of new protocols and standards. Organized into working groups that are each devoted to a specific topic or protocol. Working groups document their work in reports, called Request For Comments (RFCs). IRTF (Internet Research Task Force): The Internet Research Task Force is a composed of a number of focused, long-term and small Research Groups. Internet Architecture Board (IAB): a technical advisory group of the Internet Society, provides oversight of the architecture for the protocols and the standardization process The Internet Engineering Steering Group (IESG): The IESG is responsible for technical management of IETF activities and the Internet standards process. Standards. Composed of the Area Directors of the IETF working groups.

Internet Standardization Process Working groups present their work i of the Internet are published as RFC (Request for Comments). RFCs are the basis for Internet standards. Not all RFCs become Internet Standards ! (There are >3000 RFCs and less than 70 Internet standards A typical (but not only) way of standardization is: Internet Drafts RFC Proposed Standard Draft Standard (requires 2 working implementation) Internet Standard (declared by IAB)

Assigning Identifiers for the Internet Who gives University the domain name “netlab.edu” and who assigns it the network prefix “128.143.0.0/16”? Who assigns port 80 as the default port for web servers? The functions associated with the assignment of numbers is referred to as Internet Assigned Number Authority (IANA). Early days of the Internet: IANA functions are administered by a single person (Jon Postel). Today: Internet Corporation for Assigned Names and Numbers (ICANN) assumes the responsibility for the assignment of technical protocol parameters, allocation of the IP address space, management of the domain name system, and others. Management of IP address done by Regional Internet Registries (RIRs): APNIC (Asia Pacific Network Information Centre) RIPE NCC (Réseaux IP Européens Network Coordination Centre) ARIN (American Registry for Internet Numbers) Domain names are administered by a large number of private organizations that are accredited by ICANN.

Summary Layered Internet architecture Reduce complexity Higher layer views lower layer as service provider Application layer, transport layer, network layer, and link layer