networking principles | My Assignment Tutor

25/09/20171• Understand IP addressing anddomain name servers.• DHCP, static versus dynamic IPaddressing, reservations,scopes, leases, options (DNSservers, suffixes), IP helper,DHCP relay, DNS records,Dynamic DNS.• Install and configure networkservices and applications.ObjectivesOBJECTIVESLO1 Examine networking principles and their protocols Used by 95% of all TCP/IP applications Communication rules require sending and receiving machines toacknowledge the other’s presence and readiness Chops up data into segments Each segment has a sequence number Each application is assigned a specific port number on which tolisten/send ACK in action25/09/20172 “Fire-and-forget” protocol Used when data must simply be sent without worrying about a fewdropped pieces here and there Very fast protocol Examples: VoIP, DHCP, and DNS Used by Domain Name System (DNS) and Dynamic HostConfiguration Protocol (DHCP) Overcomes limitations of Ethernet networks Unique IP address per host Unique address per logical network Communicate between LANs without constant broadcasts25/09/2017332-bit valueExample:11000000101010000000010000000010Broken into four groups of eight11000000.10101000.00000100.00000010Each 8-bit value is converted into a decimalnumber between 0 and 255 Private IP addresses through Class A network block) through Class B network block) through Class C network block) All other IP addresses are public IP addresses25/09/20174 Overcomes limitations of Ethernet networks Unique IP address per host Unique address per logical network Communicate between LANs without constant broadcasts32-bit valueExample:11000000101010000000010000000010Broken into four groups of eight11000000.10101000.00000100.00000010Each 8-bit value is converted into a decimalnumber between 0 and 25525/09/20175 Binary Decimal00000000 000000001 100000010 200000011 300000100 400000101 500000110 600000111 700001000 8 Binary Decimal11111000 24811111001 24911111010 25011111011 25111111100 25211111101 25311111110 25411111111 255  Converted address in dotted decimal notation 11000000101010000000010000000010is displayed as 11000000.10101000.00000100.00000010 Know how to convert dotted decimal to binary and back Every OS has a calculator25/09/20176 Decimal to binary conversion Enter a value in decimal view Switch to binary view to convert the value Leading zeroes do not display in the calculator Leading zeroes are important when working with IP addresses Every MAC address must be unique on a network Every IP address must be unique Every computer on a small TCP/IP network has both an IP address anda MAC address An operating system utility displays addresses A command-line utility is also availableA smallnetwork withboth IP andMACaddresses25/09/20177Macintosh OS X Network utilityipconfig /all results25/09/20178Results from running ifconfig in Ubuntu IP addresses support LANs and WANs Functions of IP Creates a way to use IP addresses so each LAN has its ownidentification Interconnects all LANs using routers Gives each computer a way to recognize whether a packet is for theLAN or the WAN25/09/20179 All computers on same LAN must sharea similar IP address First group of numbers will be the same Last group of numbers will be unique Number of zero values at the end determines maximum number ofhosts Examples: limited to 254 addresses has a total of 65,534 hosts has a total of 16.7 million hosts Network IDs allow make it possible to connect multiple LANs into aWAN25/09/201710 Different processes used to send a packet to local and remotecomputers Local computer: send a broadcast Remote computer: send packet to the default gateway Processes are illustrated in Figures 7.21 and 7.22 Subnet mask String of ones followed by some number of zeros25/09/201711StepsThe sending computer compares the destination IP address to its own IPaddress using the subnet maskIf the destination IP address matches the computer IP wherever there’sa 1 in the subnet mask, the destination is localIf not, the address is remoteComparing addresses For a local destination address, sending computer sends out an Address ResolutionProtocol (ARP) broadcast to determine the destination computer’s MAC address An ARP packet contains the sending computer’s IP address and the destination address The destination computer responds by sending an ARP response containing its MACaddress The sending computer can now send data packets to the destination25/09/20171211111111111111111111111100000000 = = = = /24 (24 ones)11111111111111110000000000000000 = /16 (16 ones)11111111000000000000000000000000 = /8 (8 ones)IP Address Classes25/09/201713 Practice and defines IP addressNetworking 25Dynamic Host ConfigurationProtocol (DHCP)Local Area Networking Technologies 2625/09/201714 Every device that connects to a network needs an IP address. Network administrators assign static IP addresses to routers, servers,and other network devices whose locations (physical and logical) arenot likely to change. User computers in an organisation often change locations, physicallyand logically. Desktop clients do not require a static address. A workstation can use any address within a range ofaddresses. This range is typically within an IP subnet.Local Area Networking Technologies 27 Administrators typically prefer a network server to offer DHCPservices. Scalable Relatively easy to manage. In a small branch or SOHO location, a Cisco router can beconfigured to provide DHCP services without the need for anexpensive dedicated server.Local Area Networking Technologies 2825/09/201715 Address Allocation Methods: Manual: The IP address for the client is pre-allocated by the administrator andDHCP conveys the address to the client. Automatic: DHCP automatically assigns a permanent IP address to a client with nolease period. Dynamic: DHCP assigns, or leases, an IP address to the client for a limited period oftime.Local Area Networking Technologies 29 Dynamic Allocation: DHCP works in a client/server mode. When the client connects, the server assigns or leases anIP address to the device. The device connects to the network with that leased IPaddress until the lease period expires. The host must contact the DHCP server periodically toextend the lease. The leasing of addresses assures that addresses that are nolonger used are returned to the address pool for use byother devices.Local Area Networking Technologies 3025/09/201716 Dynamic Allocation: 4 Step Process. DHCPDISCOVER: The client broadcasts a DHCPDISCOVER message. The DHCPDISCOVER message finds the DHCP server(s) on the network.Local Area Networking Technologies 31 Dynamic Allocation: 4 Step Process. DHCPOFFER: The server responds with a DHCPOFFER. The DHCPOFFER message is sent as a unicast and containsan available IP address to lease.Local Area Networking Technologies 3225/09/201717Dynamic Allocation: 4 Step Process. DHCPREQUEST: The client responds with a broadcast of a DHCPREQUEST message. When used for obtaining a lease, it serves as an acceptance notice to theselected server and an implicit decline to any other servers. Also used for lease renewal and verification.Local Area Networking Technologies 33 Dynamic Allocation: 4 Step Process. DHCPACK: The server verifies the lease information and respondswith a DHCPACK message. The client logs the information and sends an ARP requestto verify that the address is unique.Local Area Networking Technologies 3425/09/201718 Dynamic Allocation: 4 Step Process.Local Area Networking Technologies 35The developers of DHCP needed to maintaincompatibility with BOOTPAdded to support functions of DHCP.Local Area Networking Technologies 3625/09/201719Advantages of DHCP Safe and reliable configuration: DHCP prevents configuration errors. Reduced configuration management: Use of DHCP servers cangreatly reduce the time spent configuring and reconfiguringcomputers on the network. Support for mobile devices: The DHCP lease renewal process helpsensure that client configurations updated Address reuse: When a client computer moves between subnets, itsold IP address is freed for reuse. DHCP options: DHCP supports a large and extensible set of clientconfiguration parameters called options. Automatic rebinding: DHCP clients do not require a system restart torebind or renew configuration with the DHCP server.Local Area Networking Technologies 37DisadvantageSecurity requirements: DHCP requires careful attention tosecurity; it is easy to introduce rogue DHCP servers into anetwork unless authorizations are used.Point of network failure: Once in place, DHCP becomes a criticalcore service; there are risks associated with its failure of DHCP.Additional support required on routed networks: On routednetworks, there must be some method in place for supportingDHCP’s broadcast-based client-server communications. Thismeans other services or configurations are required.Local Area Networking Technologies 3825/09/201720DOMAIN NAME SERVICE (DNS)Networking 39 DNS is the Domain Name Service. DNS translates a humanreadable name to an IP address or an IP address to a domain name.The translation of a name to an IP address is called forwarddomain name service and translation of an IP address to a domainname is called reverse domain name service. History (DNS) Before DNS, all mappings were in hosts.txt /etc/hosts on Linux C:WindowsSystem32driversetchosts on Windows Centralised, manual system Changes were submitted to SRI via email Machines periodically FTP new copies of hosts.txt Administrators could pick names at their discretion Any name was allowedo christos_server_at_neu_pwns_joo_lol_kthxbyeNetwork Operating Systems 4025/09/201721 Eventually, the hosts.txt system fell apart Not scalable, SRI couldn’t handle the load Hard to enforce uniqueness of names especially when close names areused Have a look at [C:WindowsSystem32driversetchosts] Many machines had inaccurate copies of hosts.txt Thus, DNS was bornNetwork Operating Systems 41The name space is the structure of the DNS databaseAn inverted tree with the root node at the topNetwork Operating Systems 4225/09/201722The domain name service is a tree hierarchy. It starts with the top leveldomains then extends to sub domains. Examples of top level domains(TLD) are shown.Network Operating Systems 43For example, the .us primary domain server islocated in the United States. This figure showsthe top level domains and their relationship tothe sub domains and the root servers.Network Operating Systems 4425/09/201723group of servers that exist using well know IP addressthat have been programmed into DNS servers.When the DNS service is installed on a server, the rootserver’s IP addresses are automatically configured inthe DNS.The campus DNS will query the root servers to try tofind name servers of known domains.Network Operating Systems 45Root .mil .edu .net .org .ca .info .biz .tvSubdomainsTop Level Domains (TLD)Network Operating Systems 4625/09/201724Root .mil .edu .net .org .ca .info .biz .tvSubdomainsTop Level Domains (TLD)Network-A wants to know the IPaddress of the www server atNetwork-BNetwork Operating Systems 47Root .mil .edu .net .org .ca .info .biz .tvSubdomainsTop Level Domains (TLD)Network-A queries the Rootservers for the IP address forthe .edu domainDNS QueryNetwork Operating Systems 4825/09/201725Root .mil .edu .net .org .ca .info .biz .tvSubdomainsTop Level Domains (TLD)The root servers return the IPaddress for the .edu domainDNS QueryNetwork Operating Systems 49Root .mil .edu .net .org .ca .info .biz .tvSubdomainsTop Level Domains (TLD)Network-A DNS queries the .edu domainFor the IP address of the Network-BDNSNetwork Operating Systems 5025/09/201726Root .mil .edu .net .org .ca .info .biz .tvSubdomainsTop Level Domains (TLD)Network-A DNS then queriesNetwork-B DNS for the IP address ofthe www.Network-B.eduNetwork Operating Systems 51 The root servers only have information about the next level in thetree. Root servers only know about the top level domains (e.g. .com,.gov, .mil, etc.). They will not know anything about They only know the .edu domain server’s IP address.Network Operating Systems 5225/09/201727 The first step for providing DNS service for a campus network is to obtain adomain name. This requires that the user seeking the domain name go Internic has a list of name registrars where a domain can be purchased. Whenyou get on the registrars web site you will be able to input a domain name. Theregistrar will check to see if the domain name is available. If the domain name is available, you will be prompted to complete theapplication for the domain name and put in the DNS servers that are to be usedto host the domain. The DNS servers will be assigned an IP address and names. When thenetwork’s DNS servers are placed on-line, the root servers will point to thenetwork’s DNS servers.Network Operating Systems 53 The primary records are the “A” records of a campus network. Thesecontain the host name and an IP addresses for the computers. For example has an assigned IP address of a host pings , the host computer first checks itsDNS cache, assuming the DNS cache is empty, the host then sends a DNSrequest to the campus DNS server. Typically the host will know the IP addresses of the primary and secondaryDNS server either through static input or dynamic assignment. The requestis sent to the primary DNS server requesting the IP address The primary DNS server is the authority for and knows theIP address of the hosts in the network. The primary DNS server returns theIP address of and then the ICMP process associatedwith a ping is started.Network Operating Systems 5425/09/201728Networking 55 The IPv4 address space provides approximately 4,294,967,296unique addresses. Only 3.7 billion addresses are assignable.o Separates the addresses into classes.o Reserves addresses for multicasting, testing, and other specific uses. As of January, 2007, approximately 2.4 billion of the available IPv4addresses are already assigned to end users or ISPs. Despite the large number, IPv4 address space is running out.Local Area Networking Technologies 5625/09/201729 0123456789101112131415UnavailableAllocatedAvailable16,777,2161993161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250251252253254255 IPv4 Address AllocationaddressesLocal Area Networking Technologies 57 0123456789101112131415UnavailableAllocatedAvailable16,777,2162000161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250251252253254255 IPv4 Address AllocationaddressesLocal Area Networking Technologies 5825/09/201730 0123456789101112131415UnavailableAllocatedAvailable16,777,2162007161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250251252253254255 IPv4 Address AllocationaddressesLocal Area Networking Technologies 59 0123456789101112131415August2009UnavailableAllocatedAvailable16,777,216161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250251252253254255 IPv4 Address AllocationaddressesLocal Area Networking Technologies 60 Population Growth: The Internet population is growing. November 2005, Cisco estimate: 973 million users. This number has doubled since then. Users stay on longer. Reserve IP addresses for longer periods. Contacting more and more peers daily. Mobile Users: More than one billion mobile phones. More than 20 million IP-enabled mobile devices.Local Area Networking Technologies 61 Transportation: There will be more than one billionautomobiles by 2008. Newer models are IP-enabled to allow remote monitoring. Consumer Electronics: The newest home appliances allow remote monitoring using IPtechnology. e.g. Digital Video Recorders (DVRs) that download and update programguides. Home networking.Local Area Networking Technologies 6225/09/201732 The ability to scale networks for future demands requires alimitless supply of IP addresses and improved mobility. DHCP and NAT alone cannot meet these requirements. IPv6 satisfiesthe increasinglycomplexrequirementsof hierarchicaladdressingthat IPv4 doesnot provide.Local Area Networking Technologies 63 Address Availability: IPv4: 4 octets – 32 bits 2^32 or 4,294,467,295 IP Addresses. IPv6: 16 octets – 128 bits 3.4 x 10^38 or340,282,366,920,938,463,463,374,607,431,768,211,456(340 undecillion) IP Addresses. Every atom of every person on Earth could be assigned 7 uniqueaddresses with some to spare (assuming7 × 1027 atoms per human x 6.5 Billion).Local Area Networking Technologies 6425/09/201733 IPv6 Advanced Features:Local Area Networking Technologies 65 CharacteristicIPv4IPv6Formatx.x.x.x4, 8-bit fieldsSeparated by dotsx:x:x:x:x:x:x:x8, 16-bit fieldsSeparated by colonsFieldRepresentationDecimal FormatGroups of 4 hexadecimaldigits, case sensitive forA, B, C, D, E and F.Leading ZeroesOmittedOptionalSuccessive ZeroFieldsMust be includedCan be represented by “::” once in an address. Local Area Networking Technologies 6625/09/201734 IPv6 Representation – Rule 1: The leading zeroes in any 16-bit segment do not have to be written. If any16-bit segment has fewer than four hexadecimal digits, it is assumed thatthe missing digits are leading zeroes. 2031:0000:130F:0000:0000:09C0:876A:130B2031:0:130F:0:0:9C0:876A:BC008105:0000:0000:4B10:1000:0000:0000:00058105:0:0:4B10:1000:0:0:50000:0000:0000:0000:0000:0000:0000:00000:0:0:0:0:0:0:0 Local Area Networking Technologies 67 1080:0:0:0:8:800:200C:417A = 1080::8:800:200C:417AFF01:0:0:0:0:0:0:101 = FF01::1010:0:0:0:0:0:0:1 = ::10:0:0:0:0:0:0:0 = :: • IPv6 Representation – Rule 2:• Any single, contiguous string of one or more 16-bit segmentsconsisting of all zeroes can be represented once with a doublecolon.Local Area Networking Technologies 6825/09/201735 IPv6 Representation – Rule 2: Any single, contiguous string of one or more 16-bit segments consisting ofall zeroes can be represented once with a double colon.Example: 1843:f01::22::fa Illegal because the length of the two all-zero strings is ambiguous.1843:00f0:0000:0000:0022:0000:0000:00fa1843:00f0:0000:0000:0000:0022:0000:00fa 1843:00f0:0000:0022:0000:0000:0000:00faoror Local Area Networking Technologies 69 IPv6 Representation: Prefix: IPv4 prefix (the network portion of the address) can be dotted decimal orbit count. e.g. or /16 IPv6 prefix is always represented by bit count.o e.g. 3ef8:ca62:12:cc::2/6416 32 48 64Local Area Networking Technologies 7025/09/201736 IPv6 Representation: In a URL, it is enclosed in brackets. http://[2001:1:4F3A::206:AE14]:8080/index.htmlo URL parsers have to be modified.o Cumbersome for users. Mostly for diagnostic purposes. Use Fully Qualified Domain Names (FQDN). DNS MUST WORK!Local Area Networking Technologies 71 IPv6 Address Types: Unicast: Global Unicast Address. Link Local Unicast. Unique Local Unicast. Multicast. Anycast. Unlike IPv4, there is no broadcast address. There is an “all nodes multicast” which serves the same purpose.Local Area Networking Technologies 7225/09/201737Burgess, M., 2003. Principles of Network and System Administration. 2nd ed.Chichester: John Wiley and Sons Ltd.Hallberg, B., 2005. Networking: A Beginner’s Guide. 4th ed. Osborne: Mcgraw-Hill.Limoncelli, T. & Hogan, C., 2001. The Practice Of System and NetworkAdministration. London: Addison-Wesley.Lowe, D., 2005. Networking All-In-One Desk Reference For Dummies. 2nd ed. NewYork: Hungry Minds Inc..Olifer, N. & Olifer, V., 2005. Computer Networks: Principles, Technologies AndProtocols For Network Design. Chichester: John Wiley And Sons Ltd.Stallings, W., 2003. Data And Computer Communications. 7th ed. New York:Prentice Hall.Subramanian, M., (2000). Network Management: An Introduction to Principles andPractice. Chichester: Addison-Wesley.Tanenbaum, A., 2002. Computer Networks. London: Prentice Hall Ptr.JournalsThe Institute of Engineering and TechnologyNetworking 73


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