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Terms Defined


Terms Defined SONET is a method (not a network) of providing a high-speed, low error-rate, international, fiber-optic multiplexed transmission standard for interface ... – PowerPoint PPT presentation

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Title: Terms Defined

  • Terms Defined
  • SONET is a method (not a network) of providing a
    high-speed, low error-rate, international,
    fiber-optic multiplexed transmission standard for
    interface between the PTTs, IXCs, and LECs.
  • It also provides a technology that allows the
    major IXCs and PTTs to internationally
    standardize and control broadband network
    transport media through a common fiber interface
    called a midspan meet.
  • Vendors and service providers consider SONET a
    common interconnectivity medium for direct fiber
    services such as SMDS and ATM

  • SONET uses both synchronous and asynchronous
    transfer modes through the use of a fixed
    data-transfer frame format including user data,
    management, maintenance, and overhead.
  • SONET standards have been introduced in three
  • Phase I Hardware specifications
  • Phase II multiple vendor connectivity and
  • Phase III builds upon Phase II providing
    additional network management, performance
    monitoring, and control functions.

  • The SONET Optical Carrier (OC-N) structure
    consists of OC-N levels multiplexed to form
    higher-speed transport circuits that range into
    the gigabits range and provide an alternative to
    aggregating multiple DS1 and DS3 transmission
  • The basic structure of SONET is built around
    Synchronous Transport Signal level 1 (STS-1)
    transport through an Optical Carrier (OC-N)
    signal over fiber optics.
  • An aggregate 51,84 Mbps STS-1 bit stream, when
    converted from electrical to fiber optic is
    called Optical Carrier-1 (OC-1)
  • It is composed of a transmission of 810-byte
    frames sent at a rate of 8000 times per second.

  • SONET STRUCTURE (Continue)
  • Current SONET speeds range from 51.84 Mbps (OC-1)
    to 9.95328 Gbps (OC-192)
  • Any subrate signals below OC-1 are multiplexed to
    form a single OC-1 channel.
  • Refer to Table 15.1 (p. 597)
  • Refer to Table 15.2 (p. 597)

  • Multiplexing
  • SONET provides direct multiplexing of both SONET
    speeds and current asynchronous and synchronous
    services into the STS-N payload.
  • Payload types range from DS1 and DS3 to OC-3c and
    OC-12c ATM and SDH/PDH payloads.
  • Refer to Figure 15.1 (p.598)
  • Other major advantage of SONET is that each
    individual signal down to the DS1 level can be
    accessed without the need to demultiplex and
    remultiplex the entire OC-N level signal.
  • This is commonly accomplished through a SONET
    Digital Cross-Connect (DXC)

  • Multiplexing (Continue)
  • It is important to note that SONET multiplexing
    requires an extremely stable clocking source with
    a stable reference point.
  • Thus, the frequency of every clock within the
    network must be the same or synchronous with one
  • This central clocking source must be at least a
    Stratum level 3 source, with a Stratum 1
    preferred for greatest accuracy.

  • SONET Architecture Layers
  • There are four layers to the SONET architecture
  • physical defines the physcial fiber type, path,
    and characteristics
  • section builds the SONET frames from either
    lower SONET interfaces or electrical interfaces
  • line provides synchronization, channel
    multiplexing, and protection switching.
  • path manages the actual data transport across
    the SONET network, as well as the pointer
  • Refer to Figure 15.2 (p. 599)
  • Refer to Figure 15.3 (p. 600)

  • OC-N Midspan Fiber Meet
  • The OC-N midspan fiber meet allows CPE, LEC, and
    IXC hardware from different vendors to interface
    with each other via SONET.
  • It provides a single platform base for access
    from the central office to the CPE
  • Refer to Figure 15.5 (p. 601)

  • Data communications Channels (DCC)
  • SONET transmissions also contain communications
    channels which transmit network management
    information between network elements.
  • This information includes alarm, control,
    maintenance, and general monitoring status.
  • Each SONET terminal and regenerator uses a 192
    kbps channel, and each optical line between
    terminal multiplexers uses a 576 kbps channel for
    the DDC

  • Frame Format and OAM Elements
  • SONET frame payloads are not synchronized by a
    common clock even though SONET is a synchronous
  • The standard SONET frame has two major pieces -
    payload and overhead - functional in Phase I
  • Refer to Figure 15.6
  • Payload
  • The payload is defined as the actual data to be
    transported across the SONET path.
  • Payloads can vary depending on the OC speed of

  • Payload (continue)
  • Payloads can take many forms, such as typical
    T-carrier channels (e.g., DS3), FDDI, SMDS, ATM,
    or Virtual Tributaries (VTs) of various sizes.
  • Payloads are backward compatible with the North
    American, European, and Pacific Rim standard
    transport technologies (DS and CEPT)
  • The payload envelope of the frame can vary in
    size in 774-byte increments, and the term used
    for the envelope is Synchronous Payload Envelope
  • SONET uses pointers to provide synchronization
    to avoid having timing and slipping problems

  • Virtual Tributary
  • Virtual tributaries are the building blocks of
    the CPE.
  • The label VTxx designates virtual tributaries of
    xx Mbps.
  • These virtual tributaries are labeled as VT1.5
    for DS1, VT3 for DS1C (3 Mbps), VT2 for CEPT E1,
    and VT6 for DS2 (6 Mbps).
  • Refer to Table 15.3 (p. 607)
  • VTs are combined to form VT groups. These VT
    groups consist exclusively of three VT1.5s, four
    VT2s, two VT3s, or one VT6 within a 9-row by
    12-column portion of the SPE

  • Virtual Tributary (continue)
  • VTs can either operate in
  • locked mode - fixes the VT structure within an
    STS-1 and is designated for channelized operation
  • floating mode - allows these values to be
    changed by cross-connects and switches and is
    designated for unchannelized operation.
  • The common tributary is VT1.5, which supports a
    virtual tributary of 1.5 Mbps through a DS1
    transport envelope.
  • VTs run from the VT1.5 through a VT6 (DS2)
  • Refer to Table 15.4 (p. 608)

  • Synchronization and Pointers
  • pointers are used by SONET devices to easily
    identify subchannels down to the DS0 level within
    a SONET transmission.
  • These pointers are located within the line
    overhead portion of each frame.
  • Refer to Figure 15.12 (p. 609)
  • pointers are lso used to identify virtual
    tributaires (VTs) within an SPE

  • Overhead and the Control Field
  • The SONET overhead structure parallels the
    existing telephone network, with three layers to
    match section, line, and path segments.
  • Refer to Figure 15.13 (p. 609)
  • Bit Interleave Parity Check (BIP-8)
  • Parity is provided through a 1-byte Bit
    Interleave Parity (BIP-8) code at each section,
    line and path segment of the frame.
  • The section BIP assures error-free transport
    between regenerators,
  • The line BIP assures error-free transport between
    terminating devices
  • The path BIP assures error-free transport between
    line termination equipment.

  • Bit Stuffing
  • When the incoming tributary data rates cannot
    fully meet the STS-N rate, the SONET device
    performs bit stuffing to achieve the desired
  • This is as simple as inserting extra bits into
    the data stream, which are then stripped off at
    the destination SONET device.
  • Bit stuffing is also used for frame
    synchronization. This technique is used when the
    access hardware and network hardware are using
    different timing sources having clock frequency

  • OAM Structure
  • The Operations, Administration, and Maintenance
    (OAM) functions of SONET are divided into three
  • F1 defines OAM flows between regenerator
    sections and between regenerators and LTE
  • F2 defines OAM flows between LTEs at the
    termination of section end points.
  • F3 defines OAM flows between PTE elements that
    perform payload assembly and disassembly, error
    check operations, and cell delineation over the
    transmission path.

  • SONET Hardware
  • The most common equipment term used is the SONET
  • The word terminal, or terminal adapter, is used
    at times to represent a SONET multiplexer, DXC,
    and even a switch.
  • OC-N -to-OC-N SONET devices, those that provide
    the interface of OC-12 and OC-48 speeds to
    higher-speed tributaries like OC-192, are most
    often called terminals as well.
  • The primary benefit of SONET Central Office (CO)
    terminal equipment - terminals, multiplexers,
    terminal multiplexers, DXCs, and switches - is
    the reduction of equipment required for DS1, DS3,
    and OC-N connectivity and interswitch trunking.

  • SONET Terminating Multiplexers
  • Terminating multiplexers provide user access to
    the SONET network
  • Terminating multiplexers, also called PTE, turn
    electrical interfaces into optical signals by
    multiplexing multiple DS1, DS1C, DS2, DS3, or E1
    VTs into the STS-N signals required for OC-N
  • These devices are configured in point-to-point
    configurations. The most common is the
    point-to-point, four-fiber configuration over the
    line, where two fibers are connected between
    two terminals
  • Refer to Figure 15.16 (p. 614)

  • SONET Terminating Multiplexers
  • SONET terminals are typically connected in fiber
    rings, with each device connected to another
    through a two-pair fiber configuration.
  • Refer to Figure 15.17 (p. 614)
  • For SONET transmission LTE terminal adapters are
    also used which interface up to 84 DS1s into a
    single OC-3 interface
  • Refer to Figure 15.18 (p. 615)

  • SONET Concentrators
  • SONET concentrators operate the same way as
    electrical concentrators and hubs, concentrating
    OC-3, OC-12, and OC-48 interfaces into
    higher-transmission rates like OC-192.
  • SONET Add/Drop Multiplexer (SADM)
  • SONET add/drop multiplexers allow the provider to
    drop and add not only the lower SONET rates, but
    also electrical interface rates down to the DS1
  • Drop-and-insert, drop-and-continue, and broadcast
    mode are standard features.
  • Refer to Figure 15.19 (p. 616)

  • SONET Digital Loop Carrier Systems (DLCs)
  • Digital Loop Carrier systems (DLCs) are used to
    concentrate multiple DS0 traffic from remote
    terminals into a single OC-3 signal.
  • These devices are typically situated at the LEC
    and handle both voice and data traffic, providing
    an interface for non-SONET CPE, LEC, and CO
    switches to the SONET public network.\
  • DLCs have many capabilities and can handle access
    for many of the data services such as N-ISDN and

  • SONET Digital Cross-Connects (SDXCs)
  • SDXCs allow switching and circuit grooming across
    all levels fo the transmission down to the DS1
    level, including those that interface to the SDXC
    without being on the incoming or outgoing
  • SDXCs provide SONET OC-N level cross-connect
    provisioning capabilities and can also act as a
    SONET hub to provide both asynchronous and
    synchronous user or network access.

  • SONET Digital Cross-Connects (SDXCs) (Continue..)
  • SONET DXCs use pointers rather than traditional
    DXC slip buffers to mark the beginning of a DS1
    frame and allow insertion/extraction with minimal
  • The additional SDXC features include
  • Network monitoring and testing
  • Network provisioning
  • Maintenance
  • Network restoration
  • Refer to Figure 15.20 (p. 618)

  • SONET Digital Cross-Connects (SDXCs) (Continue..)
  • SDXCs come into two types
  • Wideband (WDXC) lower-speed device which
    provides cross-connect capability for floating
    VTs within an STS-N
  • Broadband (BDXC) higher-speed device which can
    both cross-connect at DS3 (asynchronous or
    synchronous) and STS-1 signals and provide
    concatenation of multiple STS-1 signals to STS-N

  • SONET Broadband Switches
  • SONET broadband switches provide the switching
    capability found in major voice switches, but
    operate at the higher OC-N levels.
  • Many SONET terminal and switch vendors are now
    including SDXC capabilities within their
  • A need also exists for this functionality in the
    CPE environment interfacing many LAN and MAN
  • Refer to Figure 15.23 (p. 620)

  • SONET Regenerators and Optical Amplifiers
  • Regenerators reshape and boost signals that have
    incurred dispersion or attenuation over long
    transmission distances.
  • SONET Equipment Vendors
  • SONET hardware terminal vendors can be separated
    into three categories
  • category 1 vendors pushing the SONET DXC
  • category 2 vendors offer drop-and-insert
    multiplexer products.
  • Category 3 vendors advocate integrated SONET
    message switches.
  • Most systems today are being installed at OC-48
    speeds, with some deployment of OC-192 systems,
    and are all new hardware devices.

  • Interfaces
  • The Network-Node Interface (NNI) specifies the
    link between existing in-place digital
    transmission facilities and the SONET network
    node, as well as the process for converting the
    electrical signal into optical pulses for network
  • This is the primary interface from the electronic
    world into the optical world.
  • There are three major SONET interface options
  • Direct CPE or CO hardware interface
  • Gateway device to convert to OC levels
  • Conversion within the SONET switch itself

  • Services Support
  • Typical services to ride over SONET networks
  • Digital Data Service (DDS)
  • N-ISDN
  • ATM
  • X.25/X.75
  • Frame Relay
  • 802.6/SMDS
  • With SONET, users will be able to dial up
    whatever bandwidth increments are needed.

  • Configuring the Catalyst 1900 Switch

  • Configure the Catalyst 1900 Switch CLI
  • Configure the Catalyst 1900 Switch Hostname and
  • Configure the Catalyst 1900 Switch Security
  • Configure Virtual LANs
  • Configure ISL Routing

Features of the 1900 Switch
  • Types of Operating Systems
  • IOS-based
  • Set-based
  • The Three Configuration Options
  • Command Line Interface (CLI)
  • Visual Switch Manager (VSM)
  • Original Menu System
  • Menu-based options

Catalyst 1900 Switch
Cisco 1900 IOS Configuration Commands
  • Set the passwords
  • Set the hostname
  • Configure the IP address and subnet mask
  • Identify the interfaces
  • Set a description on the interfaces
  • Define the duplex of a port
  • Verify the configuration

IOS Commands (cont.)
  • Setting the Passwords
  • Setting the User Mode and Enable Mode Passwords
  • Setting the Enable Secret Password

IOS Commands (cont.)
  • Setting the Hostname
  • Setting IP Information
  • Configuring Switch Interfaces
  • 10BaseT Interfaces
  • FastEthernet Interfaces
  • Setting Descriptions
  • Viewing Descriptions

IOS Commands (cont.)
  • Configuring the Port Duplex
  • Options
  • Verifying IP Connectivity
  • Erasing the Switch Configuration
  • Managing the MAC Address Table
  • Setting Permanent MAC Address Entries
  • Setting Static MAC Address Entries

IOS Commands (cont.)
  • Configuring Port Security
  • Using the Show Version command
  • Changing the LAN Switch Type

Configuring VLANs
  • Example
  • gten
  • config t
  • Enter configuration commands, one per line. End
  • CNTL/Z
  • (config)hostname 1900EN
  • 1900EN(config)vlan 2 name sales
  • 1900En(config)vlan 3 name marketing
  • 1900En(config)vlan 4 name mis
  • 1900EN(config)exit

Configuring VLANs
  • Assigning Switch Ports to VLANs
  • Configuring Trunk Ports
  • Clearing VLANs from Trunk Ports
  • Verifying Trunk Ports
  • Configuring ISL Routing

Configuring VTP
  • Configuring the Domain
  • Adding to a VTP Domain
  • VTP Pruning

Restoring or Upgrading the Catalyst 1900 IOS
  • Command
  • copy tftp//tftp_host_address/IOS_filename opcode
  • Backing Up and Restoring the Catalyst 1900

CDP with the 1900 Switch
  • Commands
  • sh cdp
  • cdp timer
  • cdp holdtime

  • Configured the Catalyst 1900 Switch CLI
  • Configured the Catalyst 1900 Switch Hostname and
  • Configured the Catalyst 1900 Switch Security
  • Configured Virtual LANs
  • Configured ISL Routing
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