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HSN_Unit_1

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    HIGH SPEED

    NETWORKS

    Unit-I

    HIGH SPEED NETWORKS

    By

    K Eugine Raj

    AP/SCAD Engg College

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    FRAME RELAY NETWORKS

    Switching in the data communication physical

    layer is mainly done by three category.

    Circuit switching is used in public telephone

    networks and is the basis for private

    networks.

    Packet switching was designed to provide a

    more efficient circuit switching for bursty data

    traffic.

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    SIMPLE SWITCHING NETWORK

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    CIRCUIT-SWITCHING NETWORKS

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    CIRCUIT ESTABLISHMENT

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    PACKET-SWITCHING PRINCIPLES

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    PACKET SWITCHING: DATAGRAM APPROACH

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    PACKET SWITCHING: DATAGRAM APPROACH

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    PACKET SWITCHING: DATAGRAM APPROACH

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    PACKET SWITCHING: VIRTUAL-CIRCUIT

    APPROACH

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    PACKET SWITCHING: VIRTUAL-CIRCUIT

    APPROACH

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    X.25

    X.25 is an ITU-T standard that

    specifies an interface between a host

    system and a packet-switching

    network.

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    FRAME RELAY

    Frame relay is designed to provide a more

    efficient transmission scheme than X.25.

    The standards for frame relay entered in the

    market before ATM had arrived.

    The traditional approach to packet switchingmakes use of X.25.

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    Frame relay is designed to eliminate much of the

    overhead that X.25 imposes on end usersystems and on the packet-switching network.

    Differences between frame relay and a

    conventional X.25 packet-switching service are.

    Call control signaling

    Multiplexing and switching of logical connections

    takes place at layer 2 instead of layer 3,

    eliminating one entire layer of processingNo hop-by-hop flow control and error control

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    FRAME RELAY USER-NETWORK INTERFACE

    PROTOCOL ARCHITECTURE

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    CONTROL PLANE

    It offers similar service to that of a common

    channel signaling for circuit-switching services,

    in that a separate logical channel is used for

    control information.

    At the data link layer, LAPD (Q.921) is used to

    provide a reliable data link control service, witherror control and flow control, between user

    (TE) and network (NT).

    This data link service is used for the exchange

    of Q.933 control signaling messages.

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    USER PLANE

    For the actual transfer of information

    between end users, the userplane

    protocol is LAPF (Link Access

    Procedure for Frame Mode Bearer

    Services), which is defined in Q.922.

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    USER DATA TRANSFER

    The operation of frame relay for user data

    transfer is best explained by considering the

    frame format, illustrated in Figure

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    ASYNCHRONOUSTRANSFERMODE

    ATM is a streamlined packet transfer interface.

    ATM makes use of fixed-size packets, calledcells.

    The use of a fixed size and fixed format results

    in an efficient scheme for transmission overhigh-speed networks.

    ATM provides both real-time and non-real-time

    services.

    An ATM based network can support a widerange of traffic, include synchronous TDM

    streams

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    ATM PROTOCOL ARCHITECTURE

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    User plane: Provides for user

    information transfer, along with

    associated controls (e.g., flow control,

    error control)

    Control plane: Performs call controland connection control functions

    Management plane: Includes plane

    management and layer management.

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    ATM LOGICAL CONNECTIONS

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    ATM LOGICAL CONNECTIONS

    Logical connections in ATM are referred to as

    virtual channel connections (VCCs).

    A VCC is set up between two end users

    through the network and a variable-rate, full-

    duplex flow of fixed-size cells is exchangedover the connection.

    For ATM, a second sublayer of processing has

    been introduced that deals with the concept of

    virtual path.A virtual path connection (VPC) is a bundle

    of VCCs that have the same end points.

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    ADVANTAGES

    Simplified network architecture

    Increased network performance and

    reliability

    Reduced processing and short connectionsetup time

    Enhanced network services

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    VIRTUAL CHANNEL CONNECTION USES

    The endpoints of a VCC may be end

    users, network entities, or an end user

    and a network entity.

    Between end users.

    Between an end user and a network

    entity

    Between two network entities

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    VIRTUAL PATH/VIRTUAL CHANNEL

    CHARACTERISTICS

    Quality of service (QoS).

    Switched and semipermanent virtual

    channel connections.

    Cell sequence integrity.

    Traffic parameter negotiation and

    usage monitoring.

    Virtual channel identifier restriction

    within a VPC

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    ATM CELLS

    The asynchronous transfer mode

    makes use of fixed-size cells, consistingof a 5-octet header and a 48-octet

    information field.

    Advantages of using small, fixed-sizecells are,

    First, the use of small cells may reduce

    queuing delay.Second, it appears that fixed-size cells

    can be switched more efficiently.

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    HEADER FORMAT

    The Generic Flow Control (GFC) field

    appear in the cell header at the user-network interface.

    Hence, it can be used for control of cell

    flow only at the local user-networkinterface.

    The Virtual Path Identifier (VPI)

    constitutes a routing field for the network.

    It is 8 bits at the user-network interface

    and 12 bits at the network-network

    interface.

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    The Virtual Channel Identifier(VCI) isused for routing to and from the enduser.

    The Payload Type (PT) field indicatesthe type of information in the informationField.

    The Cell Loss Priority (CLP) bit isused to provide guidance to the networkin the event of congestion.

    The Header Error Control (HEC) fieldis used for both error control andsynchronization, as explainedsubsequently.

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    ATM SERVICE CATEGORIES

    An ATM network is designed to be able to

    transfer many different types of trafficsimultaneously, including real-time flows

    such as voice, video, and bursty TCP

    flows.Each data flow is handled within the

    network depends on the characteristics of

    the traffic flow and the requirements of the

    application.

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    ATM SERVICE CATEGORIES

    Real-Time Service

    Constant bit rate (CBR)

    Real-time variable bit rate (rt-VBR)

    Non-Real-Time Service

    Non-real-time variable bit rate (nrt-

    VBR)

    Available bit rate (ABR)Unspecified bit rate (UBR)

    Guaranteed frame rate (GFR)

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    REAL-TIME SERVICES

    In real time applications a flow of information

    to a user that is intended to reproduce thatflow at a source. For example, a user

    expects a flow of audio or video information.

    Constant Bit Rate (CBR) The CBR service

    is perhaps the simplest service to define.

    CBR is commonly used for uncompressed

    audio and video information.

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    CONSTANT BIT RATE

    CBR applications include

    Videoconferencing

    Interactive audio (e.g., telephony)

    Audio/video distribution (e.g.,

    television, distance learning, pay-per-

    view)

    Audio/video retrieval (e.g., video-on-

    demand, audio library)

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    REAL-TIME VARIABLE BIT RATE (RT-VBR)

    The rt-VBR category is intended for time-

    sensitive applications.For example, the standard approach to

    video compression results in a sequence

    of image frames of varying sizes.Because real-time video requires a

    uniform frame transmission rate, the actual

    data rate varies.Statistically multiplex a number of

    connections over the same dedicated

    capacity

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    NON-REAL-TIME SERVICES

    Non-real-time services areintended for applications that

    have bursty traffic.

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    NON-REAL-TIME VARIABLE BIT RATE

    (NRT-VBR)

    For some non-real-time applications, it is

    possible to characterize the expected traffic

    flow so that the network can provide

    substantially improved QoS in the areas ofloss and delay.

    Such applications can use the nrt-VBR

    service.

    Examples include airline reservations, bankingtransactions, and process monitoring.

    U B R (UBR)

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    UNSPECIFIED BIT RATE (UBR)

    At any given time, a certain amount of the

    capacity of an ATM network is consumed incarrying CBR and the two types of VBR traffic.

    Additional capacity is available for one or both

    of the following reasons:

    (1) Not all of the total resources have been

    committed to CBR and VBR traffic, and

    (2) the bursty nature of VBR traffic means that

    at some times less than the committedcapacity is being used.

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    All of this unused capacity could be

    made available for the UBR service.This service is suitable for applications

    that can tolerate variable delays and

    some cell losses, which is typically trueof TCP-based traffic.

    Examples of UBR applications include

    Text/data/image transfer, messaging,distribution, retrieval

    Remote terminal (e.g., telecommuting)

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    AVAILABLE BIT RATE (ABR)

    To improve the service provided to

    bursty sources that would otherwise

    use UBR, the ABR service has been

    defined.

    An application using ABR specifies a

    peak cell rate (PCR) that it will use and

    a minimum cell rate (MCR) that it

    requires.

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    GUARANTEED FRAME RATE (GFR)

    The most recent addition to the set of ATM

    service categories is GFR, which is designed

    specifically to support IP backbone

    subnetworks.

    GFR provides better service than UBR forframe-based traffic, including IP and Ethernet.

    A major goal of GFR is to optimize the

    handling of frame-based traffic that passes

    from a LAN through a router onto an ATMbackbone network.

    HIGH SPEED LANS

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    HIGH SPEED LANS

    The IEEE 802.3 standard, known as Ethernet,

    now encompasses data rates of 10 Mbps, 100Mbps, 1 Gbps, and 10 Gbps.

    For the lower data rates, the CSMA/CD MAC

    protocol is used.

    For the 1-Gbps and 10-Gbps options, a switchedtechnique is used.

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    ETHERNET

    The most widely used high-speed

    LANs today are based on Ethernetand were developed by the IEEE

    802.3 standards committee.

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    IEEE 802.3 100-MBPS SPECIFICATIONS

    (FAST ETHERNET)

    Fast Ethernet refers to a set of

    specifications developed by the IEEE

    802.3 committee to provide a low-cost,

    Ethernet-compatible LAN operating at100 Mbps.

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    GIGABIT ETHERNET

    The strategy for Gigabit Ethernet is the same as

    that for Fast Ethernet.

    Gigabit Ethernet retains the CSMA/CD protocol

    and Ethernet format of its 10-Mbps and

    100Mbps predecessors. It is compatible with 100BASE-T and 10BASE-T,

    preserving a smooth migration path.

    As more organizations move to 100BASE-T,

    putting huge traffic loads on backbonenetworks, demand for Gigabit Ethernet has

    intensified.

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    10-GBPS ETHERNET

    The principle driving requirement for 10

    Gigabit Ethernet is the increase in

    Internet and intranet traffic.

    A number of factors contribute to the

    explosive growth in both Internet and

    intranet traffic.

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    FIBRE CHANNEL

    Fibre Channel is designed to combine

    the best features of both technologies

    the simplicity and speed of channel

    communications with the flexibility andinterconnectivity that characterize

    protocol-based network

    communications.

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    WIRELESS LANS

    Wireless LAN is one that makes

    use of a wireless transmission

    medium.

    Wireless LAN ApplicationsLAN extension, cross building

    interconnect, nomadic access, and

    ad hoc networks.

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    IEEE 802.11 ARCHITECTURE AND

    SERVICES