Network Access and Transmission Methods

1. Network Access and Transmission Methods Tan Alam School of IT Bond University

2. LAN Topologies • Physical Topology – the physical/geographical layout of the network or segment. • Logical Topology – how information flows on the network

3. Physical Bus Topology (traditionally called a Daisy Chain)

4. Physical Ring Topology

5. Physical Star Topology

6. Hybrid Physical Topologies (combinations of topologies to form an extended network)

7. WAN Topologies • Layout of connected networks • Mesh – network connected to many other networks directly • Partial Mesh – not connected to all others • Full mesh – everyone connected directly to each other • Also Star and Bus like LAN

8. Mesh Topologies

9. Mesh Topologies

10. ETHERNET • A network access method originally developed by Xerox in the 1970s and later improved by Xerox, Digital Equipment Corporation (DEC), and Intel. • Can be implemented with a variety of network media, including both wireline and wireless channels • Traditionally a physical and logical Bus topology – Daisy Chain directly connecting one host or node to the next. • This network was limited in length by the connecting medium – but this was quite long. • Our networks grew bigger – we wanted to connect more hosts and also peripheral devices (eg. Printers)

11. ETHERNET Next Generation Ethernet used a Hub as a central point to connect all hosts – this is still a bus – think of it as just making the drop cable longer. • Each hub became a network segment that we could connect to another network segment. • This allowed us to extend the physical length of the network by connecting hubs together. • Ethernet is a Data Link Layer protocol – it transmits FRAMES between nodes.

12. Ethernet transmissions • Ethernet Frame - each frame contains a 15-byte header (4 fields) and a 4-byte frame check sequence (FCS) field. • CSMA/CD – Access method - rules for how nodes are able to transmit and receive frames. • CS - Carrier Sense – each host must check if the connection is free before starting its transmission process. • MA - Multiple Access - refers to the fact that multiple nodes can be connected to a network segment and all have equal opportunity to monitor and transmit information. • CD - Collision Detection – If more then one host transmits at the same time the two transmissions will collide on the connection. Collision detection process defines how to recognise this, what to do if it happens and how/when to retransmit the original message.

13. Ethernet – CSMA/CD

14. Ethernet • Coaxial Cable – insulted single strand copper wire cabling • 10Base5 - Coaxial Cable(Thick-net) – 10Mbps, baseband, 500m maximum segment length • 10Base2 – Coaxial Cable(Thin-net) – 10Mbps, baseband, 185m (200approx) maximum segment length • 10BaseT - 10Mbps, Baseband transmission and Twisted pair media(T), 100m max segment length. • All of these are ideal physical connection for Ethernet to send its frames over.

15. Ethernet

16. Ethernet

17. Common Physical layer partners for Ethernet • 10BaseFL – 10Mbps, Baseband transmission, Fibre optic cable, 2000m max segment length. • 100BaseT (also called FastEthernet) - 100Mbps, baseband transmission, Twisted pair cabling (CAT 5), 100m max segment length. • 100BaseF - 100Mbps, Baseband transmission, Fiber optic cable.

18. Switched Ethernet • Replace the Hub as a connecting device with a Switch • A Switch provides dedicated circuits to connected hosts, nodes or segments. • Switches can be used to • connect multiple segments together OR • to connect hosts within a segment together OR • Both. • Switch separates traffic and selectively forwards frames based on their destination address. • Rather then broadcasting the frames to everyone in other segments like a hub. • They do this by address allocation tables that match MAC (Media Access Control) addresses to the physical connection ports on the switch.

19. Ethernet

20. Token Ring (TR) • Transmits at either 4, 16, or 100 Mbps over STP or UTP. • Uses the token-passing routine and a star-ring hybrid physical topology. • TR switch: Ex. 16 Mbps TR network supports 40 users, each workstation has access to 0.4 Mbps. Install a TR switch that can subdivide the network into 4 logical subnetworks  provides each workstation with approximately 1.6 Mbps  effectively quadruples the bandwidth in this example

21. FDDI • FDDI - Fibre Distributed Data Interface • A network access method whose standard was originally specified by ANSI in the mid-1980s and later refined by ISO. • Uses a double ring of multimode or single mode fiber to transmit data speeds of up to 100 Mbps. • Second ring only used if there is Primary ring failure and reroutes the information back in the opposite direction to make a large folded ring.

22. FDDI

23. ATM • Asynchronous Transfer Mode - a WAN access method that enables the sending of small fixed size cells and supports multiple channels. • -data transfer rate up to 9.95 Gbps • Cells - consist of 48 bytes of data plus a five-byte header for a 53-byte cell. • Virtual circuits - logical connections between network nodes. • Switched Virtual Circuits (SVC) – exist for the duration of the individual transmission. • Permanent Virtual Circuits (PVC) – exist for the network and can be used whenever needed (always use the same route).

24. ATM • Quality of Service (QoS) - a standard that specifies that data will be delivered within a certain time period after its transmission. • Compatibility - ATM cells can support multiple types of higher-layer protocols, including IP and TCP (Internet Protocols) and (Novell Protocols).

25. Network Transmission Methods • X.25 - a set of protocols designed for long-distance data transmission and standardized by the ITU in the mid-1970s. • Maximum throughput of 2.048Mbps • Frame Relay - an updated, digital version of X.25 that also relies on packet switching. It does not guarantee the delivery of data by removing much of the error checking and correction from the X.25 protocol. • Throughput range  64kbps-45Mbps

26. ISDN • An international standard, established by the ITU for transmitting data over digital lines. • All ISDN connections are based on two types of channels: • B-Channels: employ circuit-switching techniques to carry voice, video and other types of data over the ISDN connection. (56kbps-64kbps) • D-Channels: employ packet-switching techniques to carry information about the call, such as session initiation and termination signals, caller identity, call forwarding, and conference calling signals. (16-64kbps) • You need one D-channel and can add together multiple B-channels. • ISDN is a bonding of B and D channels • 23B+D1.544 Mbps (Primary Rate Interface) • 2B+D128kbps (basic Rate Interface)

27. T-Carrier Services • The general name for a group of transmission methods that includes T1s, fractional T1s, and T3s. • T-carriers are examples of dedicated leased lines. • They are also private lines.

28. Types of T-Carriers • Signal level - the T-carrier’s Physical layer electrical signaling characteristics as defined by ANSI standards in the early 1980s. • T3 Circuit - can carry the equivalent of 672 voice or data channels, giving a maximum data throughput of 44.736 Mbps.

29. Types of T-Carriers

30. T-Carrier Connectivity • Transmission Media - T1 technology can use unshielded or shielded twisted-pair copper wiring. • CSU/DSU (Channel Service Unit/Data Service Unit) – is needed as the connection point for a T-carrier line at the customer’s site. • CSU: provides termination monitoring. • DSU: converts the digital signals used by bridges, routers and multiplexers into the digital signal sent via the cabling.

31. T-Carrier Connectivity

32. DSL – Digital Subscriber Line • Uses advanced data modulation techniques to achieve extraordinary throughput over regular phone lines. • Downstream - data traveling from the telecommunications carrier’s end office. • Upstream - data traveling from the customer to the carrier’s end office. • Types of DSL • Asymmetrical: downstream throughput is usually much higher than upstream throughput. • Symmetrical - provides equal capacity for data traveling both upstream and downstream.

33. DSL

34. DSL Connectivity

35. DSL Connectivity

36. Cable Modem Technology

37. Cable connections • Cable Modems combine cable television capabilities with data transmission over the same physical connection. • The connection between user and provider is divided into two channels. • The upstream channel contains data from the user premises. • The downstream channel combines both the TV transmission and any downstream data transmission.

38. SONET • Synchronous Optical Network: 64kbps-39.8 Gbps • TDM technique, T-carriers • Developed by Bell communications research in 1980s • Good choice for linking WANs between North America, Europe and Aisa • Integrates well with T-carriers, aggregate multiple T1s or T3s • Depends on fibre-optic transmission media

39. SONET • Ring topology • One ring acts as primary route • The other ring acts as a backup • Known as self-healing-reliable • Expensive-Typically not implemented by small or medium sized businesses • Suited for audio, video and imaging data transmission