Because there are many different types of equipment and networks, there are a variety of different technologies used to provide IP addressing for network devices. This monthâ€™s column will explain these addressing options and also the terms and concepts related to IP and Internet addressing.
Any computer or IP-addressed device on a network can be called a host. A host can be called by its IP address, or can be given a name, such as â€œNetCam 2â€ or â€œDaveâ€™s Computer.â€
Servers are computers that store and allow access to specific programs or services. Larger companies may have e-mail, database, or other types of servers for specific functions. Other users on the network can be allowed access to some or all of a certain serverâ€™s information or programs. Servers are used to concentrate data and programs, providing easier maintenance and control of computer services.
Static IP assigns a specific IP address to a specific device. These addresses typically arenâ€™t changed very often, hence the name â€œstatic.â€ New devices added to the network will need to have a compatible address programmed, and the network administrator will need to keep careful track of which devices have which particular addresses to prevent assigning the same address to multiple devices. Static IP is often used in smaller networks that do not often have devices added to them.
In many networks, there are temporary users such as outside salespeople or corporate management who wish to connect their laptop to the LAN when they visit an office location. Dynamic Host Configuration Protocol (DHCP) is an addressing program, provided automatically by a network router or gateway, which provides temporary IP addresses to network computers or devices that request them.
To set up DHCP, network administrators can select a number of options, based on the sophistication of their DHCP-equipped router or network gateway. Options include how many DHCP addresses will be issued at one time, what the range of addresses will be, how long each address will be active (DHCP Lease), and other security options.
Using DHCP greatly reduces connection difficulties for temporary users, and for networks that are often changing and/or adding computers. When DHCP is enabled, users can simply set their computers to accept an IP address, without contacting the system administrator. Windows users can simply select DHCP in the â€œInternet Protocol (TCP/IP) Propertiesâ€ window associated with the particular NIC or Wi-Fi connection to be used, and the network does the rest.
DHCP is often used by Internet Service Providers (ISPs) to provide addresses for DSL and cable modem adapters.
Gateway routers provide a method of masking the existence of LAN-connected computers and devices to the Internet. For example, when a computer on a LAN makes a request for a web page the router uses its own WAN address to make the request, masking the address of the individual computer. This firewall function helps protect individual computers from outside hacking or compromise.
However, there are instances where it is desirable for LAN-connected devices to be accessible from the Internet, as is the case for a network camera or video server that your client may wish to view from a remote location. How can the gateway router provide for such remote access, without broadcasting the internal IP addresses of LAN-connected devices?
Network Address Translation (NAT) can be programmed to provide a path for incoming Internet communications, through the gateway router, to designated LAN-connected devices.
NAT uses TCP/IP ports, which can be imagined as the different channels on a cable or satellite television system. In this example, a single cable may be connected to a television, yet it provides potentially hundreds of separate channels for viewing. What channels are available for your viewing depends on which channels have been turned on by the cable provider for your location and cable interface box.
TCP/IP ports function in a similar manner. There are thousands of available ports, with numbers ranging from 0 to 65536. Ports numbered 1024 and below are most commonly used. Some port usage is standardized, with web traffic coming to port 80 and e-mail to port 25. Ports are used to direct communications traffic through the gateway router as seen in the diagram on page 68.
In this example, the camera has been programmed to respond to communications on port 85. When an Internet user outside of the LAN wants to connect to the camera, he inputs the WAN IP address of the gateway router, 18.104.22.168, adding the suffix â€œ: 85.â€ The router has been programmed to translate Internet communication requests addressed to port 85 to the LAN IP address 192.168.1.3.
Once the port address has been programmed or changed in a device, typically that device will respond only to requests from other local LAN computers that also include the specific port address. In the above example, if the camera had been left at its default port, 80, it would respond to a communications request addressed â€œ192.168.1.3â€ from another computer on the LAN. If the port address has been changed, as in the example above, other computers on the LAN would have to use â€œ192.168.1.3:85â€ to reach the camera.
Kwa sababu kuna aina nyingi za vifaa na mitandao, kuna aina mbalimbali za teknolojia zinazotumiwa kutoa anwani ya IP kwa vifaa vya mtandao. Katika makala hii, tutaelezea njia za kuwasiliana na pia maneno na dhana zinazohusiana na IP na Internet. Kompyuta yoyote au kifaa IP-addressed kwenye mtandao inaweza kuitwa mwenyeji. "Kama vile ""Nitashindwa"" au ""Nitashindwa"" au ""Nitashindwa"" au ""Nitashindwa"" au ""Nitashindwa"" au ""Nitashindwa"" au ""Nitashindwa"" au ""Nitashindwa"" au ""Nitashindwa"" au ""Nitashindwa"" au ""Nitashindwa"" au ""Nitashindwa"" au ""Nitashindwa"" au ""Nitashindwa"" au ""Nitashindwa"" au ""Nitashindwa"" au ""Nitashindwa.""" Kampuni kubwa zinaweza kuwa na barua pepe, hifadhidata, au aina nyingine za seva kwa ajili ya kazi maalum. Watumiaji wengine kwenye mtandao wanaweza kuruhusiwa kupata baadhi au yote ya habari au programu za seva fulani. Seva hutumiwa kukusanya data na programu, kutoa matengenezo rahisi na udhibiti wa huduma za kompyuta. IP ya static ni anwani ya IP ya kipekee inayotumiwa na kifaa fulani. Kwa kawaida anwani hizi hazibadiliki mara nyingi, kwa hivyo jina la "static" linamaanisha kwamba vifaa vipya vilivyoongezwa kwenye mtandao vinahitaji kuwa na anwani inayofaa iliyoandaliwa, na msimamizi wa mtandao atahitaji kufuatilia kwa uangalifu ni vifaa gani vina anwani gani maalum ili kuzuia kugawa anwani sawa kwa vifaa vingi. Static IP ni mara nyingi kutumika katika mitandao ndogo ambayo si mara nyingi kuwa na vifaa aliongeza yao. Katika mitandao mingi, kuna watumiaji wa muda kama vile wauzaji wa nje au usimamizi wa kampuni ambao wanataka kuunganisha laptop yao kwa LAN wakati wanapotembelea eneo la ofisi. Dynamic Host Configuration Protocol (DHCP) ni programu ya anwani, zinazotolewa moja kwa moja na router mtandao au gateway, ambayo hutoa anwani za IP ya muda kwa kompyuta mtandao au vifaa kwamba kuomba yao. Ili kuanzisha DHCP, wasimamizi wa mtandao wanaweza kuchagua chaguzi kadhaa, kulingana na utaalam wa router yao iliyo na DHCP au lango la mtandao. Chaguzi ni pamoja na jinsi nyingi DHCP anwani itakuwa iliyotolewa kwa wakati mmoja, nini mbalimbali ya anwani itakuwa, ni muda gani kila anwani itakuwa hai (DHCP Lease), na chaguzi nyingine za usalama. Kutumia DHCP hupunguza sana ugumu wa muunganisho kwa watumiaji wa muda, na kwa mitandao ambayo mara nyingi hubadilisha na au kuongeza kompyuta. Wakati DHCP ni kuwezeshwa, watumiaji wanaweza tu kuweka kompyuta zao kukubali anwani ya IP, bila kuwasiliana na msimamizi wa mfumo. "Watumiaji wa Windows wanaweza tu kuchagua ""DHCP"" katika ""Internet Protocol (TCP) Properties"" dirisha kuhusishwa na NIC maalum au Wi-Fi uhusiano kutumika, na mtandao hufanya mapumziko." DHCP ni mara nyingi kutumika na Internet Service Providers (ISPs) kutoa anwani kwa DSL na cable modem adapters. Routers Gateway kutoa njia ya masking kuwepo kwa LAN-kuunganishwa kompyuta na vifaa kwa Internet. Kwa mfano, wakati kompyuta kwenye LAN hufanya ombi kwa ukurasa wa wavuti, router hutumia anwani yake mwenyewe ya WAN kufanya ombi, kufunika anwani ya kompyuta ya mtu binafsi. Kazi hii ya firewall husaidia kulinda kompyuta za mtu binafsi kutoka nje ya hacking au kuathiriwa. Hata hivyo, kuna matukio ambapo ni ya kutamaniwa kwa ajili ya vifaa LAN-kuunganishwa kuwa kupatikana kutoka Internet, kama ni kesi ya kamera ya mtandao au video server kwamba mteja wako anaweza kutaka kuona kutoka eneo la mbali. Jinsi gani router gateway inaweza kutoa kwa ajili ya upatikanaji kama mbali, bila matangazo ya ndani ya anwani za IP ya vifaa LAN-kuunganishwa? Network Address Translation (NAT) inaweza kuwa programu ya kutoa njia kwa ajili ya mawasiliano ya Internet inakuja, kupitia router gateway, kwa vifaa maalum LAN-kuunganishwa. NAT hutumia bandari za TCP na IP, ambazo zinaweza kuwa na njia tofauti za televisheni ya cable au satellite. Katika mfano huu, cable moja inaweza kuunganishwa na televisheni, lakini hutoa uwezekano wa mamia ya vituo tofauti kwa ajili ya kutazama. Vituo vya TV vinavyopatikana kwa ajili ya kutazama vinategemea ni vituo gani vilivyofunguliwa na mtoa huduma ya cable kwa eneo lako na sanduku la kiunganishi cha cable. TCP na IP bandari kazi kwa njia sawa. Kuna maelfu ya bandari zinazopatikana, na nambari kuanzia 0 hadi 65536. Vituo vya 1024 na chini ni kawaida kutumika. Kwa mfano, kwa mfano, kwa mfano, kwa mfano, kwa mfano, kwa mfano, kwa mfano, kwa mfano, kwa mfano, kwa mfano, kwa mfano, kwa mfano, kwa mfano, kwa mfano, kwa mfano, kwa mfano, kwa mfano, kwa mfano, kwa mfano, kwa mfano, kwa mfano, kwa mfano, kwa mfano, kwa mfano, kwa mfano, kwa mfano, kwa mfano, kwa mfano, kwa mfano. Vituo vya mawasiliano vya mawasiliano vya mawasiliano vya mawasiliano vya mawasiliano vya mawasiliano vya mawasiliano vya mawasiliano vya mawasiliano vya mawasiliano vya mawasiliano vya mawasiliano vya mawasiliano vya mawasiliano vya mawasiliano vya mawasiliano vya mawasiliano vya mawasiliano vya mawasiliano vya mawasiliano vya mawasiliano vya mawasiliano vya mawasiliano vya mawasiliano. Katika mfano huu, kamera imepangwa kujibu mawasiliano kwenye bandari ya 85. "Kama mtumiaji wa mtandao nje ya LAN anataka kuunganisha kamera, yeye inatoa WAN anwani ya IP ya router gateway, 18.104.22.168, kuongeza suffix ""85."" router imekuwa programu ya kutafsiri maombi ya mawasiliano ya mtandao iliyoelekezwa kwa bandari 85 kwa anwani ya IP ya LAN 192.168.1.3. """ Mara baada ya anwani ya bandari imepangwa au kubadilishwa katika kifaa, kawaida kifaa hicho kitajibu tu kwa maombi kutoka kwa kompyuta nyingine za ndani za LAN ambazo pia zina anwani maalum ya bandari. Katika mfano hapo juu, ikiwa kamera ilikuwa imeachwa kwenye bandari yake ya default, 80, itarejea ombi la mawasiliano lililoelekezwa kwa € 192.168.1.3 kutoka kwa kompyuta nyingine kwenye LAN. Ikiwa anwani ya bandari imebadilishwa, kama ilivyo katika mfano hapo juu, kompyuta nyingine kwenye LAN ingekuwa na kutumia 192.168.1.3.85 kufikia kamera.