Lecture2 - Tagged.pdf

Lecture: II  Physical Layer Cupper or Fiber optics Wires & Wireless Connections Just transmits and receives a stream of bits. No data recognition at the physical layer. Operation is controlled by protocols that define the electrical, mechanical, and procedural specifications for data transmission...

Lecture: II  Physical Layer Cupper or Fiber optics Wires & Wireless Connections Just transmits and receives a stream of bits. No data recognition at the physical layer. Operation is controlled by protocols that define the electrical, mechanical, and procedural specifications for data transmission  Serial Transmission Standards Serial transmission is the basis of most data communication between computers. There are several different serial communication standards available for use in modern computers including RS-232, USB. USB as Multi-point connectors replaces RS-232 in basic applications. RS-232 Connectors  USB Connector USB can be used to connect several devices on the same port using hubs. Twisted Pairs Cables Shielded Twisted Pair (STP) & Unshielded Twisted Pair (UTP) Unshielded Twisted Pairs (UTP) Cable  Shielded Twisted Pairs (STP) Cable Wires are Covered by Extra Shields  Signal Degradation  Attenuation is the decrease in the power of signal over a distance in a particular type of wire or media.  Coaxial Cable Coaxial cable, more commonly known as coax or cable TV cable, has specialized insulators and shielding separating two conductors allowing reliable, high speed data transmission over relatively long distances. Coax comes in various thicknesses and has been historically used in Ethernet network architectures. Modern local area network implementations rarely use coaxial cable today.  Coaxial Cable With the advent of cable modems and the use of the cable television system as a mechanism to provide high speed Internet connectivity to homes coaxial cable continues to play an important role in data communication  Fiber-Optic Cable Fiber optic cable is the current reliability and performance champion of the data communication world. Although the most expensive media choice currently available, fiber optic media delivers data transmission speeds measured in Gigabytes (billions of characters) per second over distances of measured in miles.  Fiber-Optic Cable Fiber Optic cable is also one of the most secure of all media: it is relatively un-tappable, transmitting only pulses of light, unlike all other guided media which transmit varying levels of electrical pulses. it is immune to electro-magnetic interference contributing to its high bandwidth and data transmission capabilities. Fiber Optic Cable  Cable Modems A provider of high bandwidth connectivity to customer premises is the television cable company. The cable provider’s infrastructure offers a significantly higher bandwidth to the consumer than the local loop provided by the telephone company due to the coaxial cable media used for cable television transmission  10 mbps to a House hold System 10 Base T line 2 mbps from a House hold System T1 Line  Layer 2: The Datalink Layer The data link layer provides a reliable communications link between devices. Three key functions: – error detection – error correction – flow control In LANs the data link layer can be broken down into two sub-layers: media access control (MAC) and logical link control (LLC).  Recall: Three (3) Critical Elements of Telecom Networks In any Telecom Network Design, Architecture and Analysis, you should Answer the following 3 Questions: 1. Transmission Medium: Are they Land Lines or Radiated (Wireless)? 2. What is (are) Network Access Protocols? TCP/IP, …. What is the Switching Techniques? 3. Network’s Topology (Shape)  LAN Architecture A LAN architecture like other Network’s Architecture consists of a:  Transmission Mode  Access Methodology  Network Topology No single architecture is best in all circumstances. Transmission Mode Copper Wires Wireless  Access Methodology (Protocols) CSMA/CD ( used in Bus and Star LANs) Token Passing (used in Token Rings and Token Bus LANs) Wireless LAN  Network Topology Ring Bus Star LAN Technology Architecture  LAN Topologies LAN’s have three basic physical topologies: –Bus IEEE 802.3 CSMA/CD or Ethernet Bus (Very Popular) –Ring IEEE 802.5 Token Ring –Star IEEE 802.3 Ethernet  LAN Topologies Early Ethernet LAN were typically Bus Architectures: 1. IEEE 802.3 used in Ethernet (CSMA/CD) or Star 2. IEEE 802.5 used in Token Ring Today’s Ethernet LAN were typically Star or Bus Architectures: 1. IEEE 802.3 used in Ethernet (CSMA/CD), Star, or Wireless LANs 2. IEEE 802.5 used in Token Ring.  Ethernet Ethernet can be defined as follows: Transmission Mode: Copper Wires – Access Methodology: CSMA/CD – Physical Topology: Historically—bus, currently—star and Wireless  Ethernet IEEE 802.3 is commonly referred to as “Ethernet”  IEEE 802.3 / CSMA/CD CSMA/CD (Carrier Sense Multiple Access and Collision Detection) –It is also used in Wireless LANs In CSMA each node must wait a Random Time interval after Transmitting IEEE 802.2 For All Types For Ethernet: CSM For Token Ring 80 802.11 For Wireles  LLC and MAC Sublayers LANs use two Data Link Protocols: –Contention (802.3 or CSMA) and 802.5 or Token Ring Data Link layer consists of: –LLC and MAC LLC (logical link control = IEEE 802.2) is Responsible for: –Flow Control, Error Detection, and Error Correction –Message Sequencing and Acknowledgements (ACKs) MAC (Media Access Control-IEEE 802.3 and IEEE 802.5) enables Computers to Access the Link via: –Contention or –Token Passing Ethernet LAN Architecture  Network Design, Analysis & Evaluations Principles Performance Cost Reduction Security/Auditing Availability/Reliability Manageability & Monitoring Quality of Service/Class of Service Support for Business Recovery Planning Choosing Among LAN Architectures Important Factors to be considered when selecting among LAN architectures: –Costs –Number of users supported –Transmission speed –Vendor support –Manageability –Scalability/expandability –Security –Adherence to widely accepted standards  Cost / Performance Tradeoff Ethernet – CSMA/CD Token Ring Star Speed: 10 mbps or 100 mbps in Fast LAN 4mbps or 100mbps 1mbps – 100 mbps Medium: Twisted Pair, Coax, Fiber Twisted Pair or Fiber Twisted Pair or Fiber Distance: 185 Meters Per Segment Can be Extended to 750 Meters 5 layers of Hub’s Hierarchy each up to each Hierarchy up to 20 meters Can go up to 5 segments with Repeaters with Max of 925 Meters No of Stations Supported: Max of 30 Per Cable Segment 255 50 per Hub Standard Used: IEEE 802.3 (Ethernet -CSMA/CD) IEEE 802.5 IEEE802.3 (Simple Ethernet) Cost / NIC & Other Connectors: $100 Per Station $250/Station $100/Station  Wireless LANs IEEE 802.11 standard CSMA/CD at MAC layer 802.11 frames are similar to Ethernet frames  Wireless LAN IEEE 802.11x are the wireless LAN (WLAN) WLANs are based on Star Topology CSMA is the MAC protocol for IEEE 802.11x Wi-Fi (Wireless Fidelity) is for Interoperability among WLAN products Wireless LANs (WLAN) – 802.11b 11 mbps theoretical, 4 mbps practical Shared access – sensitive to number of simultaneous users. Commonly available, inexpensive Range is measured in 100’s of feet, lower indoors. Emerging Alternatives to Full-Fledged LANs Emerging Alternatives: –Personal Area Networks (PANs) Wireless PANs (WPANs) : Bluetooth –Wireless Home Networks HomeRF Wi-Fi & other IEEE 802.11 WLANs Wireless LANs (WLAN) – 802.11b 11 Mbps theoretical, 4 Mbps practical Shared access – sensitive to number of simultaneous users Commonly available, inexpensive Range is measured in 100’s of feet, lower indoors. Voice Network Concepts Telephone calls are connected from source via circuit switching. Circuit switching originally meant that a physical electrical circuit was created from the source to the destination. The modern telephone system is commonly known as the Public Switched Telephone Network or PSTN WAN - Wide Area Network Architectures  WAN Transmission The standard for digital transmission circuits in North America is known as a T-1 with a bandwidth of 1.544Mbps. The E-1 standard for digital transmission utilized in other parts of the world provides a bandwidth of 2.048Mbps.  WAN Transmission T-1 and T-3 are by far the most common service levels delivered. T-1 service is most often delivered via 4 copper wires (2 twisted pair) T-3 service is most commonly delivered via optical fiber T1 Line  T-1 Technology CSU/DSU (Channel Service Unit/Data Service Unit). CSU/DSU device is located on the customer side of the CSU/DSU CSU / DSU device Connects Router / Telecom Switch to the carrier’s (WAN) T-1 lines at the customer premises or it Connects Routers and Telecom Switches to Ethernet LAN. A T-1 is commonly physically terminated with a male RJ-48c connector.  T-1 technology The T-1 CSU/DSU will transfer the 1.544 Mbps of bandwidth to local Ethernet LAN devices over high- speed connections such as V.35, RS-530, or RJ48c Connectors used to connect to WAN. A CSU/DSU are often able to communicate status and alarm information to network management systems via the Simple Network Management Protocol (SNMP). CSU/DSU Network Interface Device CSU/DSU Network Interface Device CSU/DSU Network Interface Device CSU/DSU Network Interface Device RJ48c Connector for T1 series Cables V.35 Cable V.35 Cable V.35 Cable V.35 Cable EIA’s RS 530 Connector  SONET and SDH SONET (Synchronous Optical Network) is an optical transmission service that makes use of TDM techniques to deliver bandwidth. The difference between T-1 and SONET is the higher transmission capacity of SONET due to its fiber optic media and the slightly different framing techniques. ANSI T1.105 and T1.106 standards. SONET and SDH CSU/DSU:  Switching Switching allows temporary connections to be established, maintained and terminated between message sources and message destinations. There are two primary switching techniques employed: circuit switching and packet switching. Recall: Basic Infrastructure Inter Office Connectors ( IOC) The circuit between the central office and customer is called the local loop The local loop is the only remaining analog component in the system.  Basic Infrastructure Telephone calls are established by a device located at the local telephone companies Central Office (CO) known as a telephone switch All voice traffic destined for locations outside of the local LATA must be handed off to the Long Distance or Inter- Exchange carrier (IXC) of the customer's choice  Now: You are hired as an Emergency or Disaster Recover Architect What would be your solution for a customer that wants Additional Access to maintain its access to network during a disaster situation? Connecting to the Internet  Connecting to the PSTN The PSTN provides a switched circuit.  Telephone Number Plans Telephone numbers are a hierarchical address method. United States telephone numbers can be broken into three basic parts: a three digit area code, a three-digit exchange, and a four digit subscriber number. System Signaling In addition to carrying the actual voice signals, the telephone system must also carry information about the call itself. This is referred to as system signaling or inter-office signaling. There are two approaches to system signaling: in band and out of band  SS7 Applications Fully digital voice communication Telephone Numbering plan (14 digits) Caller’s ID *69 to detect crank callers who hang up. *67 for not showing your phone umber.  Voice Digitization The analog POTS system has been supplanted in the modern telephone system by a combination of analog and digital transmission technologies. Converting a voice conversation to digital format and back to analog form before it reaches its destination is completely transparent to phone network users There are a limited ways the electrical pulses can be varied to represent an analog signal  Voice Digitization Pulse Amplitude Modulation  Voice Transmission Alternatives Although the PSTN has traditionally been seen as the cheapest and most effective way to transmit voice, alternative methods for voice transmission do exist. VoIP Frame Relay ATM Voice over Frame Relay Voice over ATM  ISDN Basic Rate (2B +1D) IDSN BRI (Basic Rate Interface) service offers 2 (Two) 64 Kbps channels (also called B Channels or subscriber’s lines) for Voice & Data Services One of these two 64 kbps lines is used for Voice and the other one is used for simultaneous Data communication. There is also a 16 kbps Chanel (called D Channel) Reserved for Control and Signaling  ISDN Primary Rate (2P +1D+) IDSN PRI is Similar to ISDN BRI (Basic Rate Interface) that higher Speeds, service offers two 128 Kbps channels. One of these channels is used for data while the other is used to simultaneously transmit voice. There is a 64 kbps Chanel Reserved for Control and Signaling. ISDN Connection