Basic Computer NetworksL. Budi Handoko, M.Kom.(email@example.com)Dian Nuswantoro University
Course Content (Syllabus)1. Understanding about basic concept of computer networks.2. Understanding about network applications and utilizations.3. Understanding about networks benefits and liability.4. Understanding about networks structure, achitecture, devices and topology.5. Understanding about networks reference or standardization.6. Understanding about wireless networking.7. Understanding about security and the risk.
References• Andrew S. Tanenbaum, Computer Networks, 4th Edition, Prentice Hall, 2003• S.S. Shinde, Computer Network, New Age, 2009• Libor Dotálek and Alena Kabelová, Understanding TCP/IP, Packt, 2006
Grading Guidelines• Middle Exam (20%)• Final Exam (30%)• Assignments (50%), consisting : ▫ Individual Assignment ▫ Group Assignment ▫ Attendance ▫ Project or Challange (If Any...)
Introduction to Computer Networks(Basic Concept of Computer Networks)• History (just read the books !!! We’re not on history lesson !)• Stand alone (What ???)• Term for Computer (used to be) or Devices (gadget)• Connect 2 or more devices or computers• Functions ? (communications and using available resources together)• Location ? (no problem)• Size ? (whatever)• Benefits and liablity ? (hmm... let‘s see and break them down together in the next session)
Introduction to Computer Networks (Terminology) • The Unit used on nework ▫ bit (b) smallest unit to describe a bit to flow in the network for binary data ▫ Byte (B) consisting from 8 bit in a byte ▫ For measurement can be combine with (from smallest to biggest unit) :Factor Name Symbol Factor Name Symbol Factor Name Symbol101 deka da 1027 xona X 1057 nena N102 hecto h 1030 weka W 1042 sorta S103 kilo k 1033 vunda V 1045 rinta R106 mega M 1036 uda U 1048 quexa Q109 giga G 1039 treda TD 1051 pepta PP1012 tera T 1042 sorta S 1054 ocha O1015 peta P 1045 rinta R 1057 nena N1018 exa E 1048 quexa Q 1060 minga MI1021 zetta Z 1051 pepta PP 1063 luma L1024 yotta Y 1054 ocha O
Introduction to Computer Networks(Terminology Continues) ▫ smallest unit : Factor Name Symbol Factor Name Symbol 10-1 deci d 10-39 trekto td 10-2 centi c 10-42 sotro s 10-3 milli m 10-45 rimto r 10-6 micro µ 10-48 quekto q 10-9 nano n 10-51 pekro pk 10-12 pico p 10-54 otro o 10-15 femto f 10-57 nekto nk 10-18 atto a 10-60 mikto mi 10-21 zepto z 10-63 lunto l 10-24 yocto y 10-27 xonto x 10-30 wekto w 10-33 vunkto v 10-36 unto u
Introduction to Computer Networks(Terminology Continues)• BandWidth • ISP (Internet Service Provider)• Transfer Rate • NAP (Network Access• Wi-Fi Provider)• Concentrator (Hub, Switch, • Bit is not a byte Access Point for wireless) • IP Address• NOS (Network Operating • Proxy System) • Anonymous• Autonomous System • NOC• Hacking is not cracking • DataCenter• Broadband • DRC• WiMax (Worldwide • Anything else ??? Interopeability for Microwave Access)
Introduction to Computer Networks(Advantages)• In General ▫ Easiness (bussines, education, personal, social life, informations, communications, entertaintment) ▫ Mobility (anywhere, anytime, high reliability) ▫ Efficiency (time, money, resources sharing)• Network Administrator ▫ Good salary (really ???) ▫ Control other peoples (annoyed ??? just kick off...) ▫ Faster than others (conventional) ▫ Relax (enjoy your life, seriously ???)
Introduction to Computer Networks(Disadvantages)• In General ▫ Psychology (lack of direct interaction) ▫ Personal information generally available (no more secret) ▫ Socially (abuse, pornography, bullying, fraud) ▫ Cyberterorism, Cyberwar (please watch Die Hard 4 or The Net)• Network Administrator ▫ ERROR !!! (you’re become a fugitive, a lot of people want to KILL YOU !!!)
Introduction to Computer Networks(Applications)• Communication (e-mail, chat, im, voip, vicon)• Resource Sharing (hardware and software)• Information Sharing (files, databases)• Cloud Computing (Offices, Bussiness)• Cluster Computing (Super Computer)• GRID Computing (Distributed processing)• SAN (Storage Management)• What do you need ? (Multimedia, Databases, Security, Appliance, etc)
Introduction to Computer Networks(Classification – Scale)• NFC (Near Field Communication) Super small area were covered for this type. It’s about 1 meter persquare.• PAN (Personal Area Network) Very small geographical area. Usually using bluetooth for the connection less than 25 metres per square (open space).• LAN (Local Area Network) Small geographical area (Room, Building or limited area like Campus) within 10 km to a few hundreds km.• MAN (Metropolitan Area Network) Medium geographical area (City size).• WAN (Wide Area Network) Large geographical area (country, continent, entire planet)• IPN (InterPlanetary Network) Very Large geographical area, just like what it sound, it’s inter planet network. (Seriouslly ??? Is the lecturer have a day dream ???)
Introduction to Computer Networks(Classification - Type)• Intranet Closed group network with limited scale.• Extranet Semi closed group network with medium scale.• Internet Publicy open network with large scale.
Introduction to Computer Networks(Topology - Diagram)Network topology isabout how to define sthe way in whichcomputer, printer, andothers device areconnected.A network topologydescribes the layout of thewire (or wireless) anddevices as well as the pathsused by data transmissions.
Introduction to Computer Networks(Topology – Type -> Bus)• Commonly referred to as a linear bus, all the device on a bus topology are connected by one single cable. (coaxial cable with BNC connector and terminator)• Allows information to be directed from one computer to the other. Lots of binary collision.
Introduction to Computer Networks(Topology – Type -> Star (or Tree ?)• The most commonly used achitecture in Ethernet LAN(s). Less collisions and most efficient. Using twisted pair cable and RJ45 connectort.• Larger networks use the extended star topology also known as tree topology.• When used with network device that filter frames or packets, like bridges, switches, and routers, this topology significantly reduces the traffic on the wires by sending packets only to the wires of the destination host.
Introduction to Computer Networks(Topology – Type -> Ring)• A frame travels around the ring, stopping at each node. If a node wants to transmit data, it adds the data as well as the destination address to the frame.• The frame then continues around the ring until it finds the destination node, which takes the data out of the frames. ▫ Single ring – All the devices on the network share a single cable. (upper figure) ▫ Dual ring – The dual ring topology allows data to be sent in both direction. (lower figure)• Disadvantage ? (use you logic !)
Introduction to Computer Networks(Topology – Type -> Mesh )• The mesh topology connects all devices (nodes) to each other for redundancy and fault tolerance.• It is used in WANs to interconnect LANs and for mission critical networks like those used by banks and financial institutions.• Implementing the mesh topology is expensive and difficult.
Introduction to Computer Networks(Standardization)• There are 2 important network architecture : ▫ the OSI (Open System Interconnection) reference model, and ▫ the DoD reference model which known as TCP/IP reference.• TCP/IP reference is a simplification of OSI reference.• OSI models are widely use for discusing a compter network.
Introduction to Computer Networks(Comparison of TCP/IP and OSI)
Introduction to Computer Networks(OSI Model)• A model defines the stages or tasks of a protocol as it prepares to send data ▫ Open meaning standards available to all.• The model is devided into seven distinct layers• Each subsequent layer should perform a well- defined function and the layer boundaries are designed to minimize the information flow across the interfaces
Introduction to Computer Networks(Layer 7 - Application)• Defines the format in which data should be received from or handed over to the applications• Main function is to provides a user interface (example : web browsers, e-mail clients)• Includes file, print, database, app. services• Contains a variety of protocols that are commonly needed (examples : HTTP, SMTP)
Introduction to Computer Networks(Layer 6 - Presentation)• Main function is to present the data (example : image, audio, video)• Includes encryption, compression and translation services• Contains a variety of file types (examples : JPG, AVI, MID)
Introduction to Computer Networks(Layer 5 - Session)• Main function is to facilitates exchange of data between two (or more) applications (it serves as a checkpoint and is involved in synchronizing transaction, correctly closing files, handle session, etc.)• Keeps different applications data separated• Protocols that functioning on this layer are NFS, RPC, etc.
Introduction to Computer Networks(Layer 4 - Transport)• The basic function is to accept data from the session layer, split it up into smaller units if needed, pass these to the network layer and ensure that the pieces all arrive correctly at the other end• Provides reliable delivery of data transmissions• Performs error detection• Includes end to end connection• There are 2 kind of connection at this layer which is ▫ TCP (Transmission Control Protocol) ▫ UDP (User Datagram Protocol)
Introduction to Computer Networks(Layer 3 - Network)• Main function is to ensures the data transfer between two remote computers within a particular WAN• The basic unit of transfer is a datagram that is wrapped (encapsulated) in a frame.• Provides logical addressing• Routing layer
Introduction to Computer Networks(Layer 2 – Data Link)• Main function or task is to take a raw transmission facility and transform it into a line that appears free of undetected transmission errors to the network layer (read the book please !)• Combines packets into bytes then into frames• Performs error detection (not correction)• Provides media access adressing (point-to-point)• MAC (Media Access Control) and DLC (Data Link Control)
Introduction to Computer Networks(Layer 1 - Physical)The responsibility is transmitting raw bits overcommunication channel through hubs, wires,modems, NICs (Network Interface Card) basically anything that is physical to the network
Introduction to Computer Networks(Encapsulation) User data Appl header User data TCP header Application data IP header TCP header Application dataEthernet header IP header TCP header Application data Ethernet tailer
Introduction to Computer Networks(OSI Upper Layer - Application)• DNS (Domain Name System) ▫ DNS Server also known as Name Server ▫ Provide translation domain name to IP vice versa ▫ Domain name consist a strings separated by dot ▫ TLDs consist of gTLD and ccTLD ▫ Stored in name servers as RR (Resource Records) ▫ Using UDP Transport for query on port 53 ▫ Using TCP Transport for zone transfer on port 53
Introduction to Computer Networks(OSI Upper Layer - Application)• WWW (World Wide Web) ▫ Consisting various of informations ▫ Using tools or application known as ‘Browser’ ▫ Using HTTP (HyperText Transfer Protocol) as the protocol ▫ Using HTML (HyperText Markup Language) as the primary session ▫ Using TCP as the transport on port 80 ▫ Support for SSL Extension for secure connection
Introduction to Computer Networks(OSI Upper Layer - Application)• E-Mail (Electronic Mail) ▫ Communication device for personals or groups ▫ Support MIME (Multipurpose Internet Mail Extensions) ▫ Using tools or applications known as Mail Client or WebMail ▫ Consisting from : MUA (Mail User Agent) MTA (Mail Transfer Agent) MDA (Mail Delivery Agent) ▫ Using TCP for the transport ▫ Protocol can be used are : Incoming (To receive the mail) POP3 (Post Office Protocol) operational on port 110 IMAP4 (Internet Message Access Protocol) operational on port 143 Outgouing (To send the email) SMTP (Simple Mail Transfer Protocol) operational on port 25
Introduction to Computer Networks(OSI Upper Layer - Application)• FTP (File Transfer Protocol)• Remote Access (TELNET, SSH, RHOST, etc)• SNMP (Simple Network Management Protocol)• File Sharing (SMB, NFS, etc)• Storage (NAS, SAN exclude for DAS)• AAA (RADIUS)• Authentication Server (LDAP, KERBEROS, NIS, etc)• NNTP, SIP, SMPP, DHCP, RTP, etc. (Can you mention at least 25 others applications ???)
Introduction to Computer Networks(OSI Upper Layer - Presentation)• Nothing more to be discuss in here• Just a bunch of file(s) format (.txt, .html, .jpg, .avi, etc)• Security and extension (MIME, TLS, SSL, etc)• Merged with Application layer
Introduction to Computer Networks(OSI Upper Layer - Transport)• TCP (Transmission Control Protocol) ▫ Reliable ▫ Offers a stream service (unit of information is a byte)• UDP (User Datagram Protocol) ▫ Unreliable ▫ Offers a datagram service to the application (unit of information is a messages)• SCTP (Stream Control Transmission Protocol)• DCCP (Datagram Congestion Control Protocol)• SPX (Sequence Packet Exchange)• ATP, FCP, RDP, etc.
Introduction to Computer Networks(OSI Lower Layer - Network)• Provide logical addressing (Internet Protocol / Internetworking Packet eXchange)• Re-route the packets (Routing Information Protocol, Border Gateway Protocol, etc.)• ICMP (Internet Control Message Protocol)• IPSec (Internet Protocol Security)• IGMP (Internet Group Multicast Protocol)• etc.
Introduction to Computer Networks(Internet Protocol Address)• The principal communication protocol used for relaying datagrams (packets) across an internetworking• Controlling the operation of the subnet• Responsible for routing packets across network boundaries, it is the primary protocol that establishes the Internet• Versions : IPv4 and IPv6
Computer Networks(TCP/IP Terminology)• Network Address / Net ID• Broadcast Address / Broadcast ID• Netmask / Bitmask / Subnet Mask• Host / Host ID / (Useable) IP Address• NAT (Network Address Translation)• NAPT (Network Address and Port Translation)• CIDR (Classless Inter-Domain Routing)• VLSM (Variable Length Subnet Masking)
Computer Networks(TCP/IP Terminology Continues)• Binary base-2 number system, represents numeric values using two symbols, 0 and 1 Example : 11000000. 10101000. 01011000. 00001000• Decimal base ten number system has ten symbol for numeral system 0-9 Example : 192.168.88.8• Hexadecimal base 16 is a positional numeral system with a radix, or base of 16. It uses sixteen distinct symbols, most often the symbols 0–9 to represent values zero to nine, and A, B, C, D, E, F (or alternatively a–f) to represent values ten to fifteen Example : C0.A8.58.08
Computer Networks(TCP/IP Terminology Continues)• Anycast a network addressing and routing methodology in which datagrams from a single sender are routed to the topologically nearest node in a group of potential receivers all identified by the same destination address.• Broadcast a method of transferring a message to all recipients simultaneously.
Computer Networks(TCP/IP Terminology Continues)• Multicast the delivery of a message or information to a group of destination computers simultaneously in a single transmission from the source creating copies automatically in other network elements, such as routers, only when the topology of the network requires it.• Unicast the sending of messages to a single network destination identified by a unique address
Introduction to Computer Networks(IPv4 Compare To IPv6)
Introduction to Computer Networks(IPv4 Compare To IPv6)
Introduction to Computer Networks(IPv6 - Features)• Larger Address Space• Aggregation-based address hierarchy – Efficient backbone routing• Efficient and Extensible IP datagram• Stateless Address Autoconfiguration• Security (IPsec mandatory)• Mobility
Introduction to Computer Networks(IPv6 - Deployment)• Dual-stack backbone Both version is used on the network and the application will select the correct address based on the type of IP traffic and particular requirements of the communication.• IPv6 over IPv4 tunneling Encapsulating IPv6 traffic within IPv4 packets, to be sent over an IPv4 backbone.• NAT-PT (Network Address Translation and Protocol Translation) Deprecated due to numerous problems.
Introduction to Computer Networks(IPv6 – Stateless Autoconfiguration)• Assign IP Address automaticaly without need of DHCP Server present• Get the address from ICMPv6 and Neighbor Discovery Protocol• Use MAC Address as the basis of IPv6 addressing• Using Modified EUI-64 (Convert EUI-48 from MAC into EUI-64 for IPv6)
Introduction to Computer Networks(IPv6 – Convert EUI-48 to EUI-64)• Reference from IEEE (RFC 2373)• Conver 48-bit MAC into 64-bit MAC by inserting FF FE in the middle of MAC Address• Invert the universal/local (U/L) flag (bit 7) in the OUI portion of the address
Introduction to Computer Networks(IPv6 – Modified EUI-64)
Introduction to Computer Networks (IPv6 – Address Space) IP IP Allocation Reference Allocation ReferencePrefix Prefix0000::/8 Reserved by IETF RFC 4291 A000::/3 Reserved by IETF RFC 42910100::/8 Reserved by IETF RFC 4291 C000::/3 Reserved by IETF RFC 42910200::/7 Reserved by IETF RFC 4048 E000::/4 Reserved by IETF RFC 42910400::/6 Reserved by IETF RFC 4291 F000::/5 Reserved by IETF RFC 42910800::/5 Reserved by IETF RFC 4291 F800::/6 Reserved by IETF RFC 42911000::/4 Reserved by IETF RFC 4291 FC00::/7 Unique Local Unicast RFC 41932000::/3 Global Unicast RFC 4291 FE00::/9 Reserved by IETF RFC 42914000::/3 Reserved by IETF RFC 4291 FE80::/10 Link Local Unicast RFC 42916000::/3 Reserved by IETF RFC 4291 FEC0::/10 Reserved by IETF RFC 38798000::/3 Reserved by IETF RFC 4291 FF00::/8 Multicast RFC 4291
Introduction to Computer Networks(IPv6 – Allocation)• 2000::/3 — Only one eighth of the total address space is currently allocated for use on the Internet.• ::/128 — The address with all zero bits is called the unspecified address (corresponding to 0.0.0.0/32 in IPv4)• ::/0 — The default unicast route (default route) address (corresponding to 0.0.0.0/0 in IPv4)• ::1/128 — The loopback address is a unicast localhost address. If an application in a host sends packets to this address, the IPv6 stack will loop these packets back on the same virtual interface (corresponding to 127.0.0.0/8 in IPv4)• fe80::/10 — Addresses in the link-local prefix are only valid and unique on a single link. Within this prefix only one subnet is allocated (54 zero bits), yielding an effective format of fe80::/64. The least significant 64 bits are usually chosen as the interface hardware address constructed in modified EUI-64 format. A link-local address is required on every IPv6- enabled interface, in other words, applications may rely on the existence of a link-local address even when there is no IPv6 routing. These addresses are comparable to the auto-configuration addresses 169.254.0.0/16 of IPv4.
Introduction to Computer Networks(IPv6 – Allocation Continues)• fc00::/7 — Unique local addresses (ULAs) are intended for local communication. They are routable only within a set of cooperating sites (analogous to the private address ranges 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 of IPv4)• Transition from IPv4 ▫ ::ffff:0:0/96 — This prefix designated an IPv4-mapped IPv6 address. With a few exceptions, this address type allows the transparent use of the Transport Layer protocols over IPv4 through the IPv6 networking application programming interface ▫ ::ffff:0:0:0/96 — A prefix used for IPv4-translated addresses which are used by the Stateless IP/ICMP Translation (SIIT) protocol ▫ 64:ff9b::/96 — The "Well-Known" Prefix. Addresses with this prefix are used for automatic IPv4/IPv6 translation ▫ 2002::/16 — This prefix is used for 6to4 addressing. Here, an address from the IPv4 network 22.214.171.124/24 is also used
Introduction to Computer Networks(IPv6 – Allocation Continues)• Special-purpose addresses ▫ 2001::/32 — Used for Teredo tunneling (which also falls into the category of IPv6 transition mechanisms) ▫ 2001:2::/48 — Assigned to the Benchmarking Methodology Working Group (BMWG) for benchmarking IPv6 (corresponding to 198.18.0.0/15 for benchmarking IPv4) ▫ 2001:10::/28 — ORCHID (Overlay Routable Cryptographic Hash Identifiers)• 2001:db8::/32 — This prefix is used in documentation. The addresses should be used anywhere an example IPv6 address is given or model networking scenarios are described (corresponding to 192.0.2.0/24, 198.51.100.0/24, and 203.0.113.0/24 in IPv4)
Introduction to Computer Networks(IPv4)• Classful addressing• Have limited number of IP Address• Have techniques to reduce addressing shortage using : ▫ Subnetting ▫ CIDR ▫ NAT
Introduction to Computer Networks(IP Address Classification)• Classification by class : ▫ Class A ▫ Class D Range 0 – 127 Range 224 – 239 Publicly available Reserved for ▫ Class B Multicasting Range 128 – 191 ▫ Class E Publicly available Range 240 – 255 ▫ Class C Experimental (used Range 192 – 223 for research) Publicly available
Introduction to Computer Networks(IP Address Classification Continues)• Classification by usages rules : ▫ Private Allocated for individual, research or NAT Can be used freely but not recognized in the internet Allocated IP’s or network’s are : 10.0.0.0/8 (Class A) 127.0.0.0/8 ( Class A and known as local loopback) 169.254.0.0/16 (Class B and known as NetZeroConf) 172.16.0.0/12 (Class B) 192.168.0.0/16 (Class C) ▫ Public Allocated for publicly usage address on internet “Can not” be used freely and recognized in the internet Usage rugulation by IANA (AfriNIC, APNIC, ARIN, LACNIC, RIPE and NCC)
Introduction to Computer Networks(IP Address Classification)• Netmask or network class : ▫ Class A Netmask : 255.0.0.0 (/8) Number of host 224 - 2 (16.777.214) ▫ Class B Netmask : 255.255.0.0 (/16) Number of host 216 – 2 (65.534) ▫ Class C Netmask : 255.255.255.0 (/24) Number of host 28 – 2 (254) ▫ Class D Netmask : 255.255.255.255 (/32) Number of host is 1 Known as point-to-point
Computer Networks(IPv4 Subnetting and Supernetting)• Subnetting ▫ Devide one large network into a few smaller network(s) ▫ Reducing broadcast domain ▫ Optimizing network performance ▫ Easy to manage ▫ Effective for large goegraphical scale network• Supernetting ▫ Contain a few smaller network (subnets) ▫ Known as Classless Network (CIDR -> developed to provide more granularity than legacy classful addressing; CIDR notation is expressed as /XX) ▫ Used for large scale of network ▫ Using VLSM (an arbitrary length between 0 and 32 bits) for deviding the addresses
Computer Networks(Illustration Subnet and Supernet)
Computer Networks(Subnetting)192.168.0.0 – 192.168.0.255• Subnet mask : 255.255.255.0• Bitmask : /24• Binary : 11111111.11111111.11111111.00000000• Network ID : 192.168.0.0• Broadcast Address : 192.168.0.255• Number of IP (2n) : 28 = 256• Number of host (2n - 2) : 28 – 2 = 254
Computer Networks(Subnetting - Exercise)• Specify for the netmask, network address, broadcast address, host, and number of IP and useable IP, block of subnet for the following address : ▫ 192.168.23.37/28 ▫ 172.16.123.109/19 ▫ 192.168.23.5/26 ▫ 10.30.2.1/22 ▫ 126.96.36.199/26
Computer Networks(Network Address Translation)• NAT is a way to conserve IP addresses• Hide a number of hosts behind a single IP address• Needed configuration for host : ▫ IP Address ▫ Subnet Mask / Netmask ▫ Network Address / Broadcast Address ▫ Gateway Address
Computer Networks(NAT - Translation Modes)• Dynamic Translation (IP Masquerading) large number of internal users share a single external address• Static Translation a block external addresses are translated to a same size block of internal addresses• Load Balancing Translation a single incoming IP address is distributed across a number of internal servers• Network Redundancy Translation multiple internet connections are attached to a NAT Firewall that it chooses and uses based on bandwidth, congestion and availability.
Computer Networks(Routing Continues)• Static Routing It is the type of routing characterized by the absence of communication between routers regarding the current topology of the network. This is achieved by manually adding routes to the routing table.• Dynamic Routing (aka. Adaptive Routing) The capability of a system, through which routes are characterized by their destination, to alter the path that the route takes through the system in response to a change in conditions. The adaptation is intended to allow as many routes as possible to remain valid (that is, have destinations that can be reached) in response to the change.
Computer Networks(Routing Protocols)• A protocol that specifies how routers communicate with each other, disseminating information that enables them to select routes between any two nodes on a computer network, the choice of the route being done by routing algorithms.• 3 major classes in widespread use on IP networks are : ▫ Interior gateway routing via link-state routing protocols, such as OSPF and IS-IS ▫ Interior gateway routing via path vector or distance vector protocols, such as RIP, IGRP and EIGRP ▫ Exterior gateway routing. BGP v4 is the routing protocol used by the public Internet.
Computer Networks(Link-state Routing Protocol)• The basic concept is that every node constructs a map of the connectivity to the network, in the form of a graph, showing which nodes are connected to which other nodes. Each node then independently calculates the next best logical path from it to every possible destination in the network. The collection of best paths will then form the nodes routing table.• The algorithm : ▫ Each link, the connected nodes and the metric is flooded to all routers ▫ Each link up/down status change is incrementally flooded ▫ Each router re-computes the routing table in parallel using the common link state database
Computer Networks(Distance Vector Routing Protocol)• Use the Bellman-Ford algorithm, Ford–Fulkerson algorithm, or DUAL FSM to calculate paths.• Requires that a router informs its neighbors of topology changes periodically.• The algorithm : ▫ Each node sends its routing table (destination distance) to all neighbors every 30 seconds ▫ Lower distances are updated with the neighbor as next hop ▫ cannot scale ▫ cannot resolve routing loops quickly
Introduction to Computer Networks(OSI Lower Layer – Data Link)• The data link layer has two sublayers : ▫ LLC (Logical Link Control) The uppermost sublayer, LLC, multiplexes protocols running atop the data link layer, and optionally provides flow control, acknowledgment, and error notification. The LLC provides addressing and control of the data link. It specifies which mechanisms are to be used for addressing stations over the transmission medium and for controlling the data exchanged between the originator and recipient machines. ▫ MAC (Media Access Control) MAC may refer to the sublayer that determines who is allowed to access the media at any one time (usually CSMA/CD). Other times it refers to a frame structure with MAC addresses inside.• Protocols ATM, SDLC, HDLC, ARP, MPLS, LAPD, CSLIP, SLIP, GFP, PLIP, IEEE 802.3, Frame Relay, ITU-T G.hn DLL, PPP, X.25, Network switch, etc.
Introduction to Computer Networks(OSI Lower Layer – Data Link Services)• Encapsulation of network layer data packets into frames• Frame synchronization• LLC : ▫ Error control (automatic repeat request,ARQ), in addition to ARQ provided by some transport-layer protocols, to forward error correction (FEC) techniques provided on the physical layer, and to error-detection and packet canceling provided at all layers, including the network layer. Data-link-layer error control (i.e. retransmission of erroneous packets) is provided in wireless networks and V.42 telephone network modems, but not in LAN protocols such as Ethernet, since bit errors are so uncommon in short wires. In that case, only error detection and canceling of erroneous packets are provided. ▫ Flow control, in addition to the one provided on the transport layer. Data-link-layer error control is not used in LAN protocols such as Ethernet, but in modems and wireless networks.• MAC : ▫ Multiple access protocols for channel-access control, for example CSMA/CD protocols for collision detection and retransmission in Ethernet bus networks and hub networks, or the CSMA/CA protocol for collision avoidance in wireless networks. ▫ Physical addressing (MAC addressing) ▫ LAN switching (packet switching) including MAC filtering and spanning tree protocol ▫ Data packet queueing or scheduling ▫ Store-and-forward switching or cut-through switching ▫ Quality of Service (QoS) control ▫ Virtual LANs (VLAN)
Introduction to Computer Networks(OSI Lower Layer - Physical)• Interfaces with the data link layers medium access control (MAC) sublayer.• Performs character encoding, transmission, reception and decoding.• Performs mandatory isolation functions.• Protocols : Modems, USB, Bluetooth, DSL, ISDN, IEEE 802.11, Ethernet, ITU, etc.
Introduction to Computer Networks(OSI Lower Layer – Physical Services)• Bit-by-bit or symbol-by-symbol delivery• Providing a standardized interface to physical transmission media, including ▫ Mechanical specification of electrical connectors and cables, for example maximum cable length ▫ Electrical specification of transmission line signal level and impedance ▫ Radio interface, including electromagnetic spectrum frequency allocation and specification of signal strength, analog bandwidth, etc. ▫ Specifications for IR over optical fiber or a wireless IR communication link• Modulation• Line coding• Bit synchronization in synchronous serial communication• Start-stop signalling and flow control in asynchronous serial communication• Circuit switching• Multiplexing (Establishment and termination of circuit switched connections)• Carrier sense and collision detection utilized by some level 2 multiple access protocols• Equalization filtering, training sequences, pulse shaping and other signal processing of physical signals• Forward error correction• Bit-interleaving and other channel coding
Introduction to Computer Networks(OSI Lower Layer – Physical Concern With)• Bit rate• Point-to-point, multipoint or point-to- multipoint line configuration• Physical network topology, for example bus, ring, mesh or star network• Serial or parallel communication• Simplex, half duplex or full duplex transmission mode• Autonegotiation
Introduction to Computer Networks(Twisted Pair Cables)• Twisted pair cabling is a type of wiring in which two conductors (the forward and return conductors of a single circuit) are twisted together for the purposes of canceling out electromagnetic interference (EMI) from external sources invented by Alexander Graham Bell• For network (ethernet) usage there are 2 kind of cables we use, which is : ▫ UTP (Unshielded Twisted Pair) ▫ STP (Shielded Twisted Pair)• The cable category for ethernet cables usually we use : Cat3, Cat4, Cat5, Cat5e, Cat6, Cat6a, Cat 7a• There are 8 core in one cable with a different unique color for each core (brown, white brown, green, white green, blue, white blue, orange, white orange)• The connector we use called RJ45• We need a crimper to create a network cable(s)• Network cables order commonly use are known as straight thru, crossover and rollover.
Introduction to Computer Networks(Network Cable Order)• Straight thru and crossover cables use for data communication• Rollover is use for console cable commonly use to configure cisco devices.• The order for each cable are :
Introduction to Computer Networks(Wireless Networking Terminology)• Wi-Fi is a mechanism for wirelessly connecting electronic devices. It is a trademark of the Wi-Fi Alliance and the brand name for products using the IEEE 802.11 family of standards.
Introduction to Computer Networks(Wireless Networking Terminology)• Fresnel Zone is one of a (theoretically infinite) number of concentric ellipsoids which define volumes in the radiation pattern of a (usually) circular aperture. Fresnel zones result from diffraction by the circular aperture.
Introduction to Computer Networks(Wireless Networking)• A wireless LAN or WLAN is a wireless local area network that uses radio waves as its carrier.• The last link with the users is wireless, to give a network connection to all users in a building or campus.• The backbone network usually uses cables.• There is a need of an access point that bridges wireless LAN traffic into the wired LAN.• The access point (AP) can also act as a repeater for wireless nodes, effectively doubling the maximum possible distance between nodes.
Introduction to Computer Networks(WLAN Common Topology)
Introduction to Computer Networks(WLAN Standard – IEEE 802.11)• A family of wireless LAN (WLAN) specifications developed by a working group at the Institute of Electrical and Electronic Engineers (IEEE)• Defines standard for WLANs using the following four technologies ▫ Frequency Hopping Spread Spectrum (FHSS) ▫ Direct Sequence Spread Spectrum (DSSS) ▫ Infrared (IR) ▫ Orthogonal Frequency Division Multiplexing (OFDM)• Versions : 802.11a, 802.11b, 802.11g, 802.11e, 802.11f, 802.11i
Introduction to Computer Networks(WLAN Standard 802.11a and 802.11b)
Introduction to Computer Networks(WLAN Standard – IEEE 802.11)
Introduction to Computer Networks(WLAN Frequency Bands ISM)• Industrial, Scientific, and Medical (ISM) bands• Unlicensed, 22 MHz channel bandwidth AM Broadcast Television Infrared wireless LAN Audio Cellular (840MHz) NPCS (1.9GHz) ExtremelyVery Low MediumHigh VeryUltra Super InfraredVisible Ultra- X-Rays Low Low High High High Light violet 902 - 928 MHz 2.4 - 2.4835 5 GHz 26 MHz GHz (IEEE 802.11) 83.5 MHz HyperLAN (IEEE 802.11) HyperLAN2
Introduction to Computer Networks(WLAN Operation Modes)• Infrastructure mode ▫ Associates with an access point ▫ All communication goes through the access point ▫ Used for wireless access at a company or campus• Peer-to-Peer (Ad Hoc) Mode ▫ If two nodes are within range of each other they can communicate directly with no access point ▫ A few users in a room could quickly exchange files with no access point required