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Lecture 03

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Lecture 03 Powered By Docstoc
					                  NETE0510
Introduction to Transmission
                Technologies
                    Supakorn Kungpisdan




     NETE0510: Communication Media and Data   1
                Communications
Outline

 General Network Topologies
 Connecting and Circuit Types and Services
 Private Leased Lines VS Switched Networks
 Transmission Basics
 Hardware Selection in the Design Process




                NETE0510: Communication Media and Data   2
                           Communications
General Network Topologies
 5 most common used network topologies:
    Point-to-point
    Multipoint (bus)
    Star
    Ring (or loop)
    Mesh
 Node: a network data communication element e.g.
  router, switch
 Link: a circuit connection between nodes
    Logical link  PVC (Permanent Virtual Circuit)
    Physical link  dedicated private link


                        NETE0510: Communication Media and Data   3
                                   Communications
Point-to-Point

 Simplest, a single link between two nodes
 Can be composed of multiple physical and/or
  logical circuits
 Most commonly used in MANs and WANs
 E.g. private line or dedicated circuit




                NETE0510: Communication Media and Data   4
                           Communications
Point-to-Point (cont’d)


             A. single link with single physical and logical circuit




                   B. single link with multiple logical circuits




    C. single path with multiple physical circuits, each carrying multiple circuits



                           NETE0510: Communication Media and Data                     5
                                      Communications
Common Bus (Multipoint)
 All nodes are physically connected to a common bus
  structure
 E.g. IEEE802.3 Ethernet protocol




                   NETE0510: Communication Media and Data   6
                              Communications
Common Bus (cont’d)

 Point-to-multipoint (broadcast) used in
  Broadband Integrated Services Digital Network
  (B-ISDN)
 Multipoint-to-point (incast)
 Multipoint-to-multipoint: combination of
  broadcast and incast




                NETE0510: Communication Media and Data   7
                           Communications
Common Bus (cont’d)




           NETE0510: Communication Media and Data   8
                      Communications
Star
 Developed during mainframe era
 Central node only provides point-to-point connections
  between any edge on wither a physical or a logical
  switched basis
 Hub and switch: physical star, logical bus
 Hub-and-spoke: a central hub site where main
  applications reside and to which all remote sites are
  connected




                    NETE0510: Communication Media and Data   9
                               Communications
Star (cont’d)




                NETE0510: Communication Media and Data   10
                           Communications
Ring
 Used in a network in which communications data flow is
  unidirectional
 IEEE 802.5 Token Ring protocol and FDDI (Fiber
  Distributed Data Interface)
    A bandwidth reservation scheme compare to the collision
     scheme used in Ethernet




                     NETE0510: Communication Media and Data    11
                                Communications
Ring (cont’d)




                NETE0510: Communication Media and Data   12
                           Communications
Mesh

 Many nodes are connected to multiple links
 Used in most switched networks, providing
  alternate routes for backup and traffic loads
 Full VS partial mesh
 No. of links in full-mesh network = n(n-1)/2 links
 Networks with n greater than 4 to 8 nodes
  employ partial mesh.



                  NETE0510: Communication Media and Data   13
                             Communications
Mesh (cont’d)




            NETE0510: Communication Media and Data   14
                       Communications
Mesh (cont’d)




            NETE0510: Communication Media and Data   15
                       Communications
Outline

 General Network Topologies
 Connecting and Circuit Types and Services
 Private Leased Lines VS Switched Networks
 Transmission Basics
 Hardware Selection in the Design Process




                NETE0510: Communication Media and Data   16
                           Communications
DCE VS DTE
 Data Communications Equipment (DCE) sits between
  Data Terminal Equipment (DTE) and transmission circuit
 DCE provides a local limited-distance physical
  connection between DTEs and terminal equipment (TE)
  e.g. computer
 DCE: e.g. modems or channel service unit/data service
  unit (CSU/DSU)
    CSU/DSU is a digital-interface device connecting a router to a
     digital circuit e.g. T1 and T3




                       NETE0510: Communication Media and Data         17
                                  Communications
DCE VS DTE (cont’d)
 DCE performs signal conversion and coding and may be
  part of DTE or intermediate equipment
 DTE converts user information into signals and
  reconverts received signals into user information
 DCE device provides clock signal and DTE devices
  synchronizes on the provided clock
 To connect DTEs, a DCE is needed
 Connecting 2 DTEs without DCE requires a null modem
  (over RS-232 interface)
 Physical medium can be two-wire, four-wire, coaxial,
  fiber optic, etc.
                  NETE0510: Communication Media and Data   18
                             Communications
Connection Types:
Simplex, Half-Duplex, and Duplex
Simplex and half-duplex




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                         Communications
Connection Types:
Simplex, Half-Duplex, and Duplex (cont’d)
Full-duplex




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                          Communications
Multidrop Circuits




             NETE0510: Communication Media and Data   21
                        Communications
Multidrop Circuits (cont’d)




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                        Communications
Private Lines and Local Loops
 A circuit leased from a service provide for a specified period
  of time
 Guarantee minimum availability, delay, throughput, and loss
 Access line or local loop: leased line used to connect other
  services
 Leased access lines can be purchased through Local
  Exchange Carriers (LECs), competitive access providers
  (CAPs), or inter-exchange carriers (IXCs)
 Expensive especially transoceanic private-line service,
  statistical multiplexing services like FR is a good alternative
 Ebrium-doping technique uses lasers to activate ebrium ion in
  fiber optic to boost signal transmitted through the fiber.



                      NETE0510: Communication Media and Data    23
                                 Communications
Outline

 General Network Topologies
 Connecting and Circuit Types and Services
 Private Leased Lines VS Switched Networks
 Transmission Basics
 Hardware Selection in the Design Process
 Review




                NETE0510: Communication Media and Data   24
                           Communications
Data Transport Networks

 Private-line or dedicated leased-line networks
 Switched networks
 Hybrid networks




                 NETE0510: Communication Media and Data   25
                            Communications
Private (Leased) Line Networks
 Leased from providers, not share with others, available
  24/7
 Simplest form of point-to-point communications
 Electrical speed conventions
    DS0 (Digital Signal 0) (56/64 Kbps)
    NxDS0 (56/64 Kbps increments)
    1.544 Mbps
    NxDS1 (1.5 Mbps increments)
 Optical speed conventions
    OC-N, where N is in increments of 51.83 Mbps
 Use leased line when always require entire bandwidth
  between two points
 Reach the highest level of security and performance
  predictability
                       NETE0510: Communication Media and Data   26
                                  Communications
Private Line Networks (cont’d)
 Require modem to transfer over analog line, CSU/DSU for digital
  line
 Traditional services:
    Analog grade service DS0, fractional DS0, DS1, fractional DS3, DS3
    Digital Data Service (DDS): more expensive, more reliability
 Optional higher bandwidth access
    SubRate Data Multiplexing (SRDM): same rate as DDS but enables
     aggregation of many low-speed channels into a single DS0 for cost
     savings
    Fractional T1 (FT1) and Fractional T3 (FT3): same type of service but at
     a DS1 and DS3 levels
 To guarantee high availability and reliability, providers has
  configured their SONET backbones to alternate facilities
  during a backbone circuit or node failure

                         NETE0510: Communication Media and Data            27
                                    Communications
Switched Networks

 Circuit and packet switched networks
 Characteristics of switched networks
  Addressing capability
  Multiple protocol and interface support
  One-to-many, many-to-one, and many-to-many
   connectivity
  Network intelligence above the physical Open Systems
   Interconnection Reference Model (OSI) layer




                  NETE0510: Communication Media and Data   28
                             Communications
Hybrid Networks

 Use private lines for predictable volumes of
  constant-bandwidth traffic
 Use switched network for users requiring one-to-
  many connectivity, bandwidth-on-demand, and
  flexible or more dynamic access




                 NETE0510: Communication Media and Data   29
                            Communications
Outline

 General Network Topologies
 Connecting and Circuit Types and Services
 Private Leased Lines VS Switched Networks
 Transmission Basics
 Hardware Selection in the Design Process




                NETE0510: Communication Media and Data   30
                           Communications
Asynchronous and Synchronous Data
Transmission
      No clock, but have start-stop bits instead




                 NETE0510: Communication Media and Data   31
                            Communications
Asynchronous and Synchronous Data
Transmission (cont’d)




            NETE0510: Communication Media and Data   32
                       Communications
Asynchronous VS Synchronous
Time Division Multiplexing




  The current approach is to carry ATDM cells over very high-speed STDM
                            NETE0510: Communication Media and Data           33
  transmission networks, such as SONET/Synchronous Digital Hierarchy (SDH)
                                       Communications
Outline

 General Network Topologies
 Connecting and Circuit Types and Services
 Private Leased Lines VS Switched Networks
 Transmission Basics
 Hardware Selection in the Design Process




                NETE0510: Communication Media and Data   34
                           Communications
Repeaters
 Offer the capability to extend an existing LAN or WAN
  segment at the L1 protocol interface
 Commonly used as signal regenerators, protecting
  against signal attenuation while improving signal quality
 Maintain integrity of all data being passed
 Completely transparent to all data content
 Form the core component of hubs
 May cause jitter
    An unwanted variation of one or more signal characteristics, such as the
     interval between successive pulses, the amplitude of successive cycles,
     or the frequency or phase of successive cycles

                         NETE0510: Communication Media and Data            35
                                    Communications
Modems
 Signals are transmitted and received over unshielded
  twisted pair phone lines
 56 Kbps using V.90 standard derived from the x2
  technology of 3Com (US Robotics) and Rockwell’s
  K56flex technology
 DSL modems use various modulation techniques
  including Discrete Multi-tone Technology (DMT), Carrier
  Amplitude Modulation (CAP), and Multiple Virtual Line
  (MVL)
 Cable modems modulate between analog and digital
  signals, and attach to the coaxial cable with a Cable
  Modem Termination System (CMTS) at the local cable
  TC company office
    27 Mbps downstream/2.5 Mbps upstream

                    NETE0510: Communication Media and Data   36
                               Communications
CSU/DSU
 Originally, Channel Service Unit (CSU) was developed to protect
  CPE (Customer Premises Equipment) from voltage surges in the
  access line
     Higher speed, used at DS1 rates
 Data Service Unit (DSU) was typically the lower-speed device,
  providing signal format and protocol translation, timing recovery, and
  synchronous sampling.
 Currently, CSU/DSU is a device that merges the CSU and DSU
  functionality
     Have the capability of Extended Super Frame (ESF) (a T1 standard that
      includes CRC check) monitoring and testing
     Advanced SNMP monitoring with their own management information
      bases (MIBs)
     Multiplex traffic from multiple input ports into a single point-to-point or
      multidrop circuit
                           NETE0510: Communication Media and Data              37
                                      Communications
CSU/DSU (cont’d)




           NETE0510: Communication Media and Data   38
                      Communications
CSU/DSU (cont’d)




           NETE0510: Communication Media and Data   39
                      Communications
CSU/DSU (cont’d)
 With the emergence of broadband service e.g. SMDS (Switched
  Multi-megabit Data Services) and ATM Data Exchange Interfaces
  (DXIs), CSU has additional function:
    Some SMDS and ATM CSUs perform some protocol conversion and
     cell segmentation
        E.g. with SMDS DXI, special SMDS CSUs takes L3_PDU frame and
         segment it into L2_PDU cells, performing part of the SMDS protocol function
         within the CSU
        Then CSU interfaces to the SMDS network through a SMDS Interface
         Protocol (SIP)
 CSU/DSU standard interfaces include 56-Kbps, FT1 (Fractional T1),
  and DS1 using EIA-232-C, V.35, and HSSI (on DS-3 models)
 CSU/DSU is a layer-1 device (except the SMDS, ATM DSU, and
  some FR CSU/DSUs)




                           NETE0510: Communication Media and Data                  40
                                      Communications
CSU/DSU (cont’d)




           NETE0510: Communication Media and Data   41
                      Communications
Hubs and LAN Switches

 Hub is Layer 1 device used to:
  combine multiple workstations or servers onto a single
   LAN segment
  Combine multiple LAN segments onto a single LAN
   segment




                   NETE0510: Communication Media and Data   42
                              Communications
Hubs and LAN Switches (cont’d)
 1st Generation hubs
    Single bus, single LAN architecture
 2nd Generation hubs
    Single bus, multiple architectures e.g. Ethernet and Token Ring
    Remote network management and configuration
 3rd Generation hubs/switches
    Multiple buses, add L2 bridging functions  L2 switch, aka smart
     hubs
    Network management e.g. SNMP
 4th Generation switching hubs
    MAC-layer switching, transparent bridging, standard wide area
     trunk interfaces
    Simple routing and elementary firewall functions
                       NETE0510: Communication Media and Data          43
                                  Communications
Hubs and LAN Switches (cont’d)
                                                    NM = Network Management




           NETE0510: Communication Media and Data                       44
                      Communications
Hubs and LAN Switches (cont’d)




           NETE0510: Communication Media and Data   45
                      Communications
Hubs and LAN Switches (cont’d)




           NETE0510: Communication Media and Data   46
                      Communications
Hubs and LAN Switches (cont’d)




           NETE0510: Communication Media and Data   47
                      Communications
Bridges
 Normally, bridges provide connectivity between LANs of
  similar architecture
 Translation bridge can translate from one media format
  to another
 Bridging can be performed in intelligent hubs, LAN
  switches, L3 switches or routers
 Pass traffic from one segment to another based on
  destination MAC address
 Store and forward packets between bridges as packet
  switches



                   NETE0510: Communication Media and Data   48
                              Communications
Bridges (cont’d)




             NETE0510: Communication Media and Data   49
                        Communications
Types of Bridging

 Transparent bridging
  Both ends of a transmission support the same physical
   media and link-layer protocols from IEEE 802.X suite
  Transparent, no part in the route discovery or selection
   process




                   NETE0510: Communication Media and Data     50
                              Communications
Transparent bridging




            NETE0510: Communication Media and Data   51
                       Communications
Types of Bridging (cont’d)

 Translating bridging
  Translate data between different physical media and link
   (MAC) protocols
  Protocols in the network layer and higher must still be
   compatible
  Do not provide segmentation services, so the frame size
   must be configured for the same supportable length
 Encapsulating bridging
  Provide a network interconnection or extension by
   placing received frames within a media-specific
   “envelope” and forwarding the encapsulated frame to
   another bridge for delivery to the destination
                   NETE0510: Communication Media and Data   52
                              Communications
Encapsulation Bridging




            NETE0510: Communication Media and Data   53
                       Communications
Source Route Bridging

 Source route bridging
  Has the ability to perform routing based on L2
   information




                   NETE0510: Communication Media and Data   54
                              Communications
Disadvantages of Bridges
 Susceptible to multicast of broadcast storms
    When bridging loop occurs
    Spanning-tree protocol (STP)


 Bridge should not be used in network designs calling for
  multiple protocol support, dynamic networks requiring
  frequent changes, or large networks of greater than 50
  nodes




                     NETE0510: Communication Media and Data   55
                                Communications
Switches

 4 classes of switches
  Workgroup or local switches: switch traffic within a
   workgroup
  Enterprise switches: connect multiple departments or
   workgroups
  Edge switches: serve as access or entry switches to a
   public data service
      Can be packet (X.25 or IP), frame (FR, Ethernet, or
       FDDI), or cell (ATM), or optical SONET/WDM switches.
  Service provider backbone (CO) switches: act as
   high-speed interconnects for edge switches

                   NETE0510: Communication Media and Data     56
                              Communications
Switches (cont’d)




            NETE0510: Communication Media and Data   57
                       Communications
Types of Switches

 L2 switches (LAN switches)
  Ethernet, Token Ring, FDDI, and ATM)
 Hybrid L2 and L3 switches
  Used when some form of packet, frame, or cell
   switching is being used, e.g. when routing IP or
   accessing FR or ATM services
  Used in backbone networks
  Perform the same tasks as routers do, but operate
   faster



                   NETE0510: Communication Media and Data   58
                              Communications
Routers
 Provide interconnectivity between devices on LANs and
  WANs
 Route packets from node to node using packet-defined
  protocol information used by routing protocols
  (routing/forwarding tables)
 Routing protocols e.g. OSPF, IGRP, RIP
 Employ address scheme, 4-byte address
 Router’s main functionality reside in L2 and L3
 Applications of both ends do not need to support the same
  LAN protocol
 Current routers can forward packets in excess of 40 mil
  packets per second

                     NETE0510: Communication Media and Data   59
                                Communications
Routers (cont’d)




            NETE0510: Communication Media and Data   60
                       Communications
Routers (cont’d)




            NETE0510: Communication Media and Data   61
                       Communications
Bridging to routing Comparison




            NETE0510: Communication Media and Data   62
                       Communications
Brouters

 Bridge + router
 Have the capability to route some protocols and
  bridge others
 Routing function is done in L2 based on MAC
  address.
  Transparent to both the network-layer protocols and end
   stations
  Do not look at the network-level addresses



                   NETE0510: Communication Media and Data   63
                              Communications
Gateway
 Provide all interconnectivity provided by routers and
  bridges, up to L7
 Can be performed in hardware, software, and both
 Slower than bridges, switches, and routers
 Protocol translator of architectures e.g. SNA, IPX.
  TCP/IP and OSI
 Translate between IEEE 802.X architectures e.g.
  between Ethernet and Token Ring
 Can reside within workstations, servers, etc.




                    NETE0510: Communication Media and Data   64
                               Communications
Gateway (cont’d)




            NETE0510: Communication Media and Data   65
                       Communications
Disadvantages of Gateway
 Low throughput during peak traffic conditions
    May become the main network’s congestion point
    Spend to much time to translate between many protocol
     suites
 User-to-gateway priority handling
 Store-and-forward characteristics

 However, gateway has a growing need for their
  functionality
 E.g. voice gateway acts as the intermediate node
  connecting a voice call between a packetized voice user
  (from an IP network) and a circuit-switched user (from
  PSTN)

                     NETE0510: Communication Media and Data   66
                                Communications
                                 Questions?
                Next Lecture
  Multiplexing and Switching
 Technologies: An Overview


NETE0510: Communication Media and Data        67
           Communications

				
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