Gateway

Internetworking DeviceInternetworking Device

GatewayGateway

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Internetworking DevicesInternetworking Devices

• RouterRouter

• GatewayGateway

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Brief Overview of RouterBrief Overview of Router

• A router operates at the physical, A router operates at the physical, data link and network layer of the data link and network layer of the OSI model.OSI model.

• It is useful for inter-connecting two or It is useful for inter-connecting two or more networks and these networks more networks and these networks may be heterogeneous.may be heterogeneous.

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• Heterogeneous means they may Heterogeneous means they may differ in their physical characteristics, differ in their physical characteristics, such as frame size, transmission such as frame size, transmission rates, topologies, addressing, etc.rates, topologies, addressing, etc.

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Problem with RouterProblem with Router

• A router can forward packets across A router can forward packets across different network types (e.g., different network types (e.g., Ethernet, Token Ring etc.).Ethernet, Token Ring etc.).

• However all these dissimilar However all these dissimilar networks must use a common networks must use a common transmission protocol (such as TCP/IP transmission protocol (such as TCP/IP or AppleTalk).or AppleTalk).

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• If the are not using the same If the are not using the same protocol, a router would not be able protocol, a router would not be able to forward packets from one network to forward packets from one network to another.to another.

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SolutionSolution

The settlement of this issue is the use The settlement of this issue is the use of a device called gateway.of a device called gateway.

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What is gatewayWhat is gateway

• A gateway can forward packets A gateway can forward packets across different networks that may across different networks that may also use different protocols. also use different protocols.

• A node on a network that serves as A node on a network that serves as an entrance to another network. an entrance to another network.

• In homes, the gateway is the ISP that In homes, the gateway is the ISP that connects the user to the internet. connects the user to the internet.

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• In enterprises, the gateway node In enterprises, the gateway node often acts as a proxy server and a often acts as a proxy server and a firewall. firewall.

• A computer system located on earth A computer system located on earth that switches data signals and voice that switches data signals and voice signals between satellites and signals between satellites and terrestrial networks. terrestrial networks.

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Application GatewayApplication Gateway

• An application gateway is also called An application gateway is also called as a proxy server. This is because it as a proxy server. This is because it acts like a proxy and decides about acts like a proxy and decides about the flow of application level traffic.the flow of application level traffic.

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It works as follows:-It works as follows:-

• An internal user contacts the application An internal user contacts the application gateway using a TCP/IP application, such as gateway using a TCP/IP application, such as HTTP or TELNET.HTTP or TELNET.

• The application gateway asks the user about The application gateway asks the user about the remote host with which the user wants the remote host with which the user wants to set up a connection for actual to set up a connection for actual communication. The application gateway communication. The application gateway also asks for the user id and the password also asks for the user id and the password required to access the services of the required to access the services of the application gateway.application gateway.

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• The application gateway now accesses The application gateway now accesses the remote host on behalf of the user, the remote host on behalf of the user, and passes the packets of the user to and passes the packets of the user to the remote host.the remote host.

• From here onwards the application From here onwards the application gateway acts like a proxy of the actual gateway acts like a proxy of the actual end user and delivers packets from the end user and delivers packets from the user to the remote host and vice versa.user to the remote host and vice versa.

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Default GatewayDefault Gateway

• A default gateway is the device that A default gateway is the device that passes traffic from the local subnet passes traffic from the local subnet to devices on other subnets. to devices on other subnets.

• The default gateway often connects The default gateway often connects a local network to the Internet, a local network to the Internet, although internal gateways for local although internal gateways for local networks also exist. networks also exist.

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Internet default gateways Internet default gateways

• On home or small business networks with On home or small business networks with a broadband router to share the Internet a broadband router to share the Internet connection, the home router serves as the connection, the home router serves as the default gateway. default gateway.

• On home or small business networks On home or small business networks without a router, such as for residences without a router, such as for residences with dialup Internet access, a router at the with dialup Internet access, a router at the Internet Service Provider location serves Internet Service Provider location serves as the default gateway. as the default gateway.

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WAP gatewayWAP gateway

• A A WAP gatewayWAP gateway sits between mobile sits between mobile devices using the WAP protocol and the devices using the WAP protocol and the World Wide Web, passing pages from World Wide Web, passing pages from one to the other much like a proxy. one to the other much like a proxy.

• This translates pages into a form This translates pages into a form suitable for the mobiles, for instance suitable for the mobiles, for instance using the Wireless Markup Language using the Wireless Markup Language (WML). (WML).

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• This process is hidden from the This process is hidden from the phone, so it may access the page in phone, so it may access the page in the same way as a browser accesses the same way as a browser accesses HTML, using a URL (for example, HTML, using a URL (for example, http://example.com/foo.wml), http://example.com/foo.wml), provided the mobile phone operator provided the mobile phone operator has not specifically prevented this. has not specifically prevented this.

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SMS gatewaySMS gateway

• One problem of SMS messaging is that One problem of SMS messaging is that SMSCs developed by different SMSCs developed by different companies use their own companies use their own communication protocol and most of communication protocol and most of these protocols are proprietary. For these protocols are proprietary. For example, Nokia has an SMSC protocol example, Nokia has an SMSC protocol called CIMD whereas another SMSC called CIMD whereas another SMSC vendor, CMG, has an SMSC protocol vendor, CMG, has an SMSC protocol called EMI. called EMI.

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• We cannot connect two SMSCs if they We cannot connect two SMSCs if they do not support a common SMSC do not support a common SMSC protocol. To deal with this problem, an protocol. To deal with this problem, an SMS gateway is placed between two SMS gateway is placed between two SMSCs. This is illustrated in the figure. SMSCs. This is illustrated in the figure. The SMS gateway acts as a relay The SMS gateway acts as a relay between the two SMSCs. It translates between the two SMSCs. It translates one SMSC protocol to another one.one SMSC protocol to another one.

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2020

ReferencesReferences

• http://en.wikipedia.orghttp://en.wikipedia.org

• Web technology by Achyut S Godbole Web technology by Achyut S Godbole & Atul Kahate.& Atul Kahate.

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Technology

Gateway