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Review of Important Networking Concepts. Introductory material. This module uses the example from the previous module to review important networking concepts: protocol architecture, protocol layers, encapsulation, demultiplexing, network abstractions. Networking Concepts .

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Review of important networking concepts

Review of Important Networking Concepts

Introductory material.

This module uses the example from the previous module to review important networking concepts: protocol architecture, protocol layers, encapsulation, demultiplexing, network abstractions.

Networking concepts
Networking Concepts

  • Layered Architecture to reduce complexity

    • Encapsulation

    • Abstractions

Sending a packet from argon to neon1

DNS: What is the IP address of “”?

DNS: The IP address of “” is

ARP: What is the MAC address of

ARP: What is the MAC address of

ARP: The MAC address of is 00:20:af:03:98:28

ARP: The MAC address of is 00:e0:f9:23:a8:20

Sending a packet from Argon to Neon is not on my local network.

Therefore, I need to send the packet to my

default gateway with address is on my local network.

Therefore, I can send the packet directly.



What s a protocol

human protocols:

“what’s the time?”

“I have a question”


… 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

What’s a protocol?

protocols define format, order of msgs sent and received among network entities, and actions taken on msg transmission, receipt

What s a protocol1

a human protocol and a computer network protocol:

TCP connection



Got the





What’s a protocol?


TCP connection



Q: Other human protocols?

Communications architecture
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 communicationsarchitectureorprotocol 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.

    TCP/IP Protocol Suite

    Functions of the layers
    Functions of the Layers the

    • 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
    TCP/IP Suite and OSI Reference Model the

    The TCP/IP protocol stack does not define the lower layers of a complete protocol stack

    Layered communications
    Layered Communications the

    • An entity of a particular layer can only communicate with:

      1. a peer layer entityusing a common protocol (Peer Protocol)

      2. adjacent layersto provide services and to receive services

    Service primitives

    N+1 Layer Peer Protocol the

    Request Delivery


    Service Primitives

    Communication services are invoked via function calls. The functions are called service primitives

    N+1 LayerEntity

    N+1 LayerEntity

    N LayerEntity

    N LayerEntity

    Service primitives1

    N+1 Layer Peer Protocol the

    Request Delivery


    Service Primitives

    Recall: A layer N+1 entity sees the lower layers only as a service provider

    N+1 LayerEntity

    N+1 LayerEntity

    Service Provider

    Layers in the example1

    Send IP data-gram to the

    Frame is an IP datagram

    Frame is an IP datagram

    IP datagram is a TCP segment for port 80

    Send HTTP Request to neon

    Establish a connection to at port 80

    Open TCP connection to port 80

    Send IP datagram to

    Send a datagram (which contains a connection request) to

    Send the datagram to

    Send the datagram to

    Send Ethernet frame to 00:e0:f9:23:a8:20

    Send Ethernet frame to 00:20:af:03:98:28

    Layers in the Example

    Layers and services
    Layers and Services the

    • 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 and demultiplexing
    Encapsulation and Demultiplexing the

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

    Encapsulation and demultiplexing in our example
    Encapsulation and Demultiplexing the 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 8990808f 4715 065b 0050 0009 465b 0000 0000 6002 2000 598e 0000 0204 05b4

    Encapsulation and demultiplexing tcp header
    Encapsulation and Demultiplexing: the TCP Header

    Option: maximum segment size

    Different views of networking
    Different Views of Networking the

    • 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 ethernet
    Network View of Ethernet the

    • Ethernet’s view of the network

    The evolution of internet

    The Evolution of Internet the

    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
    A Definition the

    • 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: the 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


    ARPAnet demonstrated publicly

    NCP (Network Control Protocol) first host-host protocol

    first e-mail program

    ARPAnet has 15 nodes

    Internet History

    1961-1972: Early packet-switching principles

    Internet history1

    1970: the 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

    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

    Internet History

    1972-1980: Internetworking, new and proprietary nets

    Internet history2

    Early 1990’s: the 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

    Internet History

    1990, 2000’s: commercialization, the Web, new apps

    Applications of the internet
    Applications of the Internet the

    • 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
    Growth of the Internet the

    Source: Internet Software Consortium

    Internet infrastructure1
    Internet Infrastructure the

    • 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 infrastructure2
    Internet Infrastructure the

    • 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
    Tier-1 ISP: e.g., Sprint the

    Sprint US backbone network

    Who is who on the internet
    Who is Who on the Internet ? the

    • 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
    Internet Standardization Process the

    • 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
    Assigning Identifiers for the Internet the

    • Who gives University the domain name “” and who assigns it the network prefix “”? 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).


    • 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 the

    • Layered Internet architecture

      • Reduce complexity

      • Higher layer views lower layer as service provider

      • Application layer, transport layer, network layer, and link layer