Data Communications and Networks Unit 9526M Level H MIKE DAWSON Introduction Welcome to the course I am Mike Dawson My email address is [email protected] You are ? What you expect from the.
Download ReportTranscript Data Communications and Networks Unit 9526M Level H MIKE DAWSON Introduction Welcome to the course I am Mike Dawson My email address is [email protected] You are ? What you expect from the.
Data Communications and Networks Unit 9526M Level H MIKE DAWSON Introduction Welcome to the course I am Mike Dawson My email address is [email protected] You are ? What you expect from the course Main Topics covered The main area’s of study IP Networking Communication Protocols Routing Switching Transport Security Course outline topics Intro to networking and Datacomms OSI 7 Layer model Layer 1 Physical bit level Layer 2 Data Link 802.2 802.3 Ethernet Bridges Routers Hubs Switches Spanning Tree VLANS Layer3 Routing ( IP ) Layer 4 Transport ( TCP/UDP ) Topic 2 IP IP addressing ClassFull – A, B, C ClassLess (VLSM) PREFIX (CIDR) Subnetting TCP UDP Topic 3 Routing Fundamentals Overview Classfull routing (RIPv1 IGRP) Classless routing (EIGRP OSPF) Distance Vector routing (RIP) Link State routing (OSPF) Convergence Case study Topic 4 Protocols Frame Relay ATM ISDN HDLC PPP OPEN SHORTEST PATH FIRST (OSPF) Algorithm derivation Dykstra Link State Components AREAS Convergence Configuring Security Secure communication PAP CHAP Radius AAA Encryption Distance Vector routing Algorithm derivation Bellman-Ford Compare – Contrast Convergence Poison reverse Split Horizon Count to Infinity Hold-downs Metrics Communication techniques CRC Encoding Error detecting codes Scramblers Manchester code NRZ code RZ code Real Life Refer to the network diagram Real life tasks will be examined IP network design IP Subnetting design Overview of applications Windows NT Novell Apple What This Means After completing this course you will be familiar with the following. Networking fundamentals Advanced networking concepts Network design IP Routing using CISCO devices Know things most people don’t understand. Get a better job .. If you want Next Steps Lets start lesson 1 Lesson 1 Basic Concepts of Internetworks, Routers and Adressing Once upon a time Mini computer (8086) Micro computer (Z80,286,386) Decentralisation Sneaker net What does this mean ? Primary Purpose of a LAN is resource sharing Pooling resources LOCAL AREA NETWORKS Centralisation Sharing resources Printers Files Applications Ethernet Media Shared medium Ethernet Media Shared medium Data Link Ethernet Media Shared medium Data Link Co-axial cable 10base2 (185m) Ethernet Media Shared medium Data Link Co-axial cable 10base2 (185m) 10baseT CAT 3,4,5 UTP Unshielded Twisted Pair RJ45 terminator upto (100m) Ethernet Media Shared medium Data Link Co-axial cable 10base2 (185m) 10baseT CAT 3,4,5 UTP Unshielded Twisted Pair RJ45 terminator upto (100m) 100baseTX CAT5,6,7 UTP RJ45 (100m) Ethernet Media Shared medium Data Link Co-axial cable 10base2 (185m) 10baseT CAT 3,4,5 UTP Unshielded Twisted Pair RJ45 terminator upto (100m) 100baseTX CAT5,6,7 UTP RJ45 (100m) 100baseFX 62.5/125micron multimode fibre 780nm laser upto (400m) Ethernet Media Shared medium Data Link Co-axial cable 10base2 (185m) 10baseT CAT 3,4,5 UTP Unshielded Twisted Pair RJ45 terminator upto (100m) 100baseTX CAT5,6,7 UTP RJ45 (100m) 100baseFX 62.5/125micron multimode fibre 780nm laser upto (400m) 1000baseLX 9-micron core, 1300 nm laser monomode fibre upto (10km) Data Link All devices attach to a common data link through some sort of Network Interface Card ( NIC ) Rules must govern communication etiquette Medium Access Control ( MAC ) IEEE 802.3 OSI data link identifiers Each devices needs a unique identifier Burned in / Physical / Machine / MAC Data link transport uses Encapsulation Encapsulation is like an electronic envelope Ethernet IEEE802.2/3 Token Ring IEEE802.5 FDDI ( HDLC encapsulation ) MAC Identifier structure MAC address is not a real address because its fixed to the device not the area the device lives. Its more like a name than an address! MAC Identifier structure MAC address is not a real address because its fixed to the device not the area the device lives. Its more like a name than an address! Ethernet MAC 48 binary bits MAC Identifier structure MAC address is not a real address because its fixed to the device not the area the device lives. Its more like a name than an address! Ethernet MAC 48 binary bits 0100 = 4 in Hexadecimal MAC Identifier structure MAC address is not a real address because its fixed to the device not the area the device lives. Its more like a name than an address! Ethernet MAC 48 binary bits 0100 = 4 in Hexadecimal 248 = 281474976710656 individual iDs MAC Identifier structure MAC address is not a real address because its fixed to the device not the area the device lives. Its more like a name than an address! Ethernet MAC 48 binary bits 0100 = 4 in Hexadecimal 248 = 281474976710656 individual iDs The above decimal number can be represented as a 48 bit binary number. MAC Identifier structure MAC address is not a real address because its fixed to the device not the area the device lives. Its more like a name than an address! Ethernet MAC 48 binary bits 0100 = 4 in Hexadecimal 248 = 281474976710656 individual iDs The above decimal number can be represented as a 48 bit binary number. 4 Binary bits make up one Hexadecimal number MAC Identifier structure MAC address is not a real address because its fixed to the device not the area the device lives. Its more like a name than an address! Ethernet MAC 48 binary bits 0100 = 4 in Hexadecimal 248 = 281474976710656 individual iDs The above decimal number can be represented as a 48 bit binary number. 4 Binary bits make up one Hexadecimal number 8 Binary bits = two Hexadecimal numbers MAC Identifier structure MAC address is not a real address because its fixed to the device not the area the device lives. Its more like a name than an address! Ethernet MAC 48 binary bits 0100 = 4 in Hexadecimal 248 = 281474976710656 individual iDs The above decimal number can be represented as a 48 bit binary number. 4 Binary bits make up one Hexadecimal number 8 Binary bits = two Hexadecimal numbers 0100.1111 = 4F Complete Task 1 Task 1 Answers 11111111 = 255 10000000 = 128 11000000 = 192 11100000 = 224 11110000 = 240 11111000 = 248 11111100 = 252 11111110 = 254 Task 1 Answers 11111111 = FF 10000000 = 80 11000000 = C0 11100000 = E0 11110000 = F0 11111000 = F8 11111100 = FC Task 1 Answers Convert Hexadecimal to Decimal FE23 = 65059 FFFF = 65535 1010 = 4112 1111 = 4369 00AB = 171 66FA = 26362 Boolean AND function Lets Logically AND the two binary numbers below 11111111 11001101 AND 11001101 Answer Network Identifiers 10101100.00010000.00010001.00001010 = 172.16.17.10 The above DOTTED DECIMAL notation is how IP addresses are represented. More on IP addressing in later lectures. OSI Layer 2 The Information presented so far may be summarised. A Data Network is one or more devices sharing a common transmission medium. Each and every device must have a unique iD Using iD’s and Encapsulation to send data in a virtual envelope A wonderful tool but.. Everybody wants one. As the LAN grows so do the problems Problem 1 Distance 1. 2. 3. Three factors Attenuation caused by the length of the cables. Interference as cables get longer there is more chance of external forces causing distortion. Distortion – As the signal gets weaker and interfered with it can become unrecognisable, hence the need for pulse regenerators. Signal degrading effects 2nd Big Problem More devices more demand for DataLink capacity. For Ethernet = more collisions For Token ring = Token rotation time > We need to do something How do we reduce the problems. 1. Make the LAN segment smaller Make the LAN segment smaller By reducing the size of the DataLink you keep local traffic local. We do this with a BRIDGE Which needs to 1st perform 4 tasks. Transparent Bridging has 4 states. 1. BLOCKING 2. LISTENING 3. LEARNING 4. FORWARDING Transparent Bridging A Transparent bridge must do the following:1. Not modify the frames it passes thru. Transparent Bridging A Transparent bridge must do the following:1. Not modify the frames it passes thru. 2. Learn by Listening where each MAC resides Transparent Bridging A Transparent bridge must do the following:1. Not modify the frames it passes thru. 2. Learn by Listening where each MAC resides 3. Build a table of MAC / Port Transparent Bridging A Transparent bridge must do the following:1. Not modify the frames it passes thru. 2. Learn by Listening where each MAC resides 3. Build a table of MAC / Port 4. Forward all Broadcasts out each port Transparent Bridging A Transparent bridge must do the following:1. Not modify the frames it passes thru. 2. Learn by Listening where each MAC resides 3. Build a table of MAC / Port 4. Forward all Broadcasts out each port 5. If no destination address is found in the forwarding table then flood the frame out all ports except the port it came in on. Transparent Bridging What is a bridge loop Preventing Bridge Loops The Spanning Tree Protocol was developed to overcome the problems of redundant links. The Spanning Tree disables redundant links Disabled redundant paths are placed into Standby mode / Blocking mode Preventing bridge loops Bridge Protocol Data Unit The BPDU is a special kind of packet used by all switches and bridges running the Spanning Tree Algorithm (STA) BPDU take part in the selection of a ROOT bridge BPDU’s are sent out every 2 sec of every port in order to maintain a loop free topology. Root Bridge Selection “I am the King” At start up each switch assumes it is the root bridge with the LOWEST iD and King. The Bridge iD = 2 byte priority + 6 byte MAC If all bridges have the same priority then the bridge with the Lowest MAC identifier will become the Root Bridge. Root Association After the root bridge has been Elected by passing BPDU’s between participating switches. Each bridge forms an association with the root via BPDU By receiving BPDU for the root on multiple ports indicates a loop path to the root. One of the ports must be blocked Calculating Path Cost STP Port States There are FOUR states for a port participating in the STA 1. Blocking Listening Learning Forwarding 2. 3. 4. Bridge Forwarding Table Finally Broadcasts FF.FF.FF.FF.FF.FF Bridges Flood Broadcasts out of all interfaces except the interface upon which it received the packet. This can cause a lot of un-necessary traffic Broadcasts have to be opened by all devices using their time and resources even if its not applicable to them In order to block broadcasts we need to segment the network logically Segmentation of LANS logically requires more sophistication. OSI LAYER 3 ROUTERS can perform this task. They can also change a DataLink encapsulation type so that Ethernet can communicate with Token Ring Answers to review questions 1.The primary purpose of a local-area network is to allow resource sharing. The resources may be devices, applications, or information. Examples of shared resources are files, databases, e-mail, modems, and printers Answers to review questions 2. A protocol is an agreed-upon set of rules. In data communications, the rules usually govern a procedure or a format. Answers to review questions 3. A Media Access Control protocol defines how a given LAN medium is shared, how LAN devices connected to the medium are identified, and how frames transmitted onto the medium are formatted . Answers to review questions 4. A frame is a digital "envelope" that provides the information necessary for the delivery of data across a data link. Typical components of a frame are identifiers (addresses) of the source and destination devices on the data link, an indicator of the type of data enclosed in the frame, and error-checking information. . Answers to review questions 5. A feature common to all frame types is a format for identifying devices on the data link an ID field or MAC address / id. Answers to review questions 6. A Media Access Control address or identifier is a means by which individual devices connected to a data link are uniquely identified for the purpose of delivering data . Answers to review questions 7. An address specifies a location. A MAC address is not a true address because it is permanently associated with the interface of a specific device and moves whenever the device moves. A MAC identifies the device, not the location of the device. Answers to review questions 8. The three sources of signal degradation on a data link are attenuation, interference, and distortion. Attenuation is a function of the resistance of the medium. Interference is a function of noise entering the medium. Distortion is a function of the reactive characteristics of the medium, which react differently to different frequency components of the signal. Answers to review questions 9. A repeater is a device that extends the useful range of a physical medium by reading a degraded signal and producing a "clean" copy of the signal Answers to review questions 10. A bridge is a device that increases the capacity of a LAN. A bridge divides the data link into segments, forwarding only traffic that is generated on one segment and is destined for another segment. By controlling and limiting the traffic on a data link, more devices may be attached to the LAN. Answers to review questions 11. A transparent bridge "listens promiscuously" on each of its ports. That is, it examines all frames on all media to which it is attached. It records the source MAC identifiers of the frames, and the ports on which it learns the identifiers, in a bridging table. It can then refer to the table when deciding whether to filter or forward a frame. The bridge is transparent because it performs this learning function independently of the devices that originate the frames. The end devices themselves have no knowledge of the bridge. Answers to review questions 12. Three fundamental differences between local-area and wide-area networks are: LANs are limited to a small geographic area, such as a single building or small campus. WANs cover a large geographic area, from citywide to worldwide. LANs usually consist entirely of privately owned components. Some components of a WAN, such as a packet switching network or point-to-point serial links, are usually leased from a service provider. A LAN provides high bandwidth at a relatively cheap price. The bandwidth across a WAN is significantly more expensive. Answers to review questions 13. A broadcast MAC identifier, when used as the destination address of a frame, signifies that the data is for all devices attached to the data link. In binary, the broadcast MAC identifier is all ones. In hex, it is FFFF.FFFF.FFFF Answers to review questions 14. The primary similarity between a bridge and a router is that both devices increase the number of hosts that, may be interconnected into a common communications net work. Answers to review questions 15. The difference is that a bridge works by interconnecting separate segments of a single network, whereas a router interconnects separate networks Answers to review questions 16. A packet is the means by which data is transported from one network to another . Answers to review questions 17. The similarity between a frame and a packet is that they both encapsulate data and provide an addressing scheme for delivering the data. Answers to review questions 18. The difference between a frame and a packet is that the frame delivers data between two devices sharing a common data link, whereas a packet delivers data across a logical pathway, or route, spanning multiple data links. Answers to review questions 19. Neither the source nor the destination address of a packet changes as it progresses from the source of the packet to the destination. Answers to review questions 20. Network addresses are the addresses used in packets . Answers to review questions 21. Each network address has a network part, which identifies a particular data link, and a host or node part, which identifies a specific device on the data link identified by the network part . Answers to review questions 22. A packet identifies a device from the perspective of the entire internetwork. A frame identifies a device from the perspective of a single data link. Because the connection between two devices across an internetwork is a logical path, a network address is a logical address. Because the connection between two devices across a data link is a physical path, a data link identifier is a physical address. Our Next Lecture will investigate in more detail the layers involved in producing this intelligent switch / routed network Thank you