What is a Protocol Converter Gateway? The Concept of Protocol Converter Gateway

 

 

 

Everyone knows that when you go from one room to another, you must pass through a door. Similarly, sending information from one network to another must also pass through a "gateway", which is the protocol converter gateway. As the name suggests, a protocol converter gateway is a "gateway" from one network to another. That is, the network gate.

 

The gateway is also known as the network connector and the protocol converter. The default gateway implements network interconnection above the network layer. It is the most complex network interconnection device and is only used for interconnection of two networks with different high-level protocols. The structure of the gateway is also similar to that of the router, the difference is the interconnection layer. Protocol converter gateways can be used for both wide area network interconnection and local area network interconnection.

 

[Note: Due to historical reasons, many documents about TCP/IP once called the router used in the network layer as the protocol converter gateway. Today, many local area networks use routing to access the network, so the gateway usually refers to the router. IP]

 

In OSI, there are two kinds of gateways: one is connection-oriented gateway and the other is connectionless gateway. When there is a certain distance between two subnets, a protocol converter gateway is often divided into two halves, and the middle is connected by a link, which is called a half gateway.

 

According to different classification standards, there are many kinds of gateways. The protocol converter gateway in the TCP/IP protocol is the most commonly used. The "gateway" we talk about here refers to the protocol converter gateway under the TCP/IP protocol.

 

So what exactly is a gateway? A protocol converter gateway is essentially an IP address from one network to other networks. For example, there are network A and network B, the IP address range of network A is "192.168.1.1~192.168.1.254", the subnet mask is 255.255.255.0; the IP address range of network B is "192.168.2.1~192.168. 2.254” and the subnet mask is 255.255.255.0. In the absence of a router, TCP/IP communication cannot be performed between two networks. Even if the two networks are connected to the same switch (or hub), the TCP/IP protocol will be based on the subnet mask (255.255 .255.0) and the host's IP address, the result of the "AND" operation is different to determine that the hosts in the two networks are in different networks. And to realize the communication between these two networks, it must go through the protocol converter gateway. If the host in network A finds that the destination host of the data packet is not in the local network, it forwards the data packet to its own gateway, and then the gateway forwards it to the gateway of network B, and the gateway of network B forwards it to a certain network B. host. This is how network A forwards packets to network B.

 

Therefore, only by setting the IP address of the gateway, the TCP/IP protocol can realize the mutual communication between different networks. So which machine's IP address is this IP address? The IP address of the protocol converter gateway is the IP address of the device with routing function. The device with routing function includes router, server with routing protocol enabled (essentially equivalent to a router), proxy server (also equivalent to a router) ).

 

In the context of interoperating with Novell NetWare networks, the Protocol Converter Gateway acts as a bridge between the Server Message Block (SMB) protocol used in Windows networks and the NetWare Core Protocol (NCP) used by NetWare networks. Gateways are also known as IP routers.

 

 

Suppose your name is Xiaobudian (very small, here you are a url address pointing to a web resource), you live in a large yard, your neighbors have many friends, and your parents are your protocol converter gateways. When you want to play with a friend in the yard, as long as you shout his name in the yard, he will respond to you and run out to play with you.

 

But your parents don't allow you to go out the door. Everything you want to contact with the outside world must be contacted by your parents (protocol converter gateway) by phone. If you want to chat with your classmate Xiao Ming, Xiao Ming lives in another yard far away, and he also has parents (Xiao Ming's protocol converter gateway). But you don't know the phone number of Xiaoming's house, but your head teacher has a list of all the students in your class and a phone number comparison table, and your teacher is your DNS server. So you have the following conversation with your parents at home:

 

Little Dot: Mom (or Dad), can I find Xiao Ming's phone number with the head teacher? Parent: OK, you wait. (Then your parent called your head teacher and asked Xiao Ming's phone number) I asked, his number is 211.99.99.99

 

Tiny: Great! Mom (or Dad), I want to find Xiao Ming, please help me contact Xiao Ming.

Parent: No problem. (Then the parent sent a request to the telephone bureau to connect to Xiaoming's phone, and of course the last level was transferred to Xiaoming's parent, and then his parent forwarded the call to Xiaoming) That's how you got in touch with Xiaoming.

 

If you know what a protocol converter gateway is, the default gateway is easy to understand. Just as a room can have multiple doors, a host can have multiple protocol converter gateways. The default protocol converter gateway means that if a host cannot find an available gateway, it will send the data packet to the default designated gateway, and the protocol converter gateway will process the data packet.

 

 

 

Manual setting is suitable for situations where the number of computers is relatively small and the TCP/IP parameters are basically unchanged, for example, there are only a few to a dozen computers. Because this method needs to set the "default gateway" on each computer connected to the network, it is very laborious. Once the IP address of the default gateway must be changed due to migration and other reasons, it will bring great trouble to the protocol converter gateway. , so it is not recommended to use it.

 

In Windows 7, the way to set the default protocol converter gateway is to right-click on "My Network Places", click "Properties" in the pop-up menu, select "TCP/IP Protocol" in the Network Properties dialog box, and click "Properties" ", fill in the IP address of the new default gateway in the "Default Gateway" tab.

 

It should be noted that the default gateway must be the IP address in the network segment where the computer is located, and cannot fill in the IP address in other network segments.

 

 

Auto setup is the use of a DHCP server to automatically assign IP addresses, subnet masks, and default protocol converter gateways to computers on the network. The advantage of this is that once the default gateway of the network is changed, as long as the default gateway setting in the DHCP server is changed, all the computers in the network will obtain the IP address of the new default gateway. This method is suitable for networks with large network scale and possible changes in TCP/IP parameters.

 

Another way to automatically obtain the gateway of the protocol converter is to obtain it automatically by installing the client program of the proxy server software (such as MS Proxy). Its principle and method are similar to DHCP. Due to space limitation, it will not be described in detail.

 

If you start to look at routing knowledge, it will be easy to understand.

Enter command line mode:

c:\>route print

There will be a route:

0.0.0.0 0.0.0.0 Default gateway's IP interface (machine's IP) hop count

For example on my machine:

0.0.0.0 0.0.0.0 192.168.100.254 192.168.100.233 1

 

Meaning: all the data packets that need to be forwarded are sent out through the IP (interface) of the default gateway, and of course the return is also passed there.

 

 

 

In order to route packets correctly and efficiently, the core gateway needs to know what is happening in other parts of the Internet, including routing information and subnet characteristics.

 

This type of information is often used when a protocol converter gateway is handling a heavy load that is extremely slow and the protocol converter gateway is the only way to access the subnet, other gateways in the network can tailor traffic to relieve the gateway load.

 

GGP is primarily used to exchange routing information, not to confuse routing information (including address, topology, and routing delay details) with the algorithms that make routing decisions. Routing algorithms are usually fixed within the protocol translator gateway and are not changed by GGP. Core gateways communicate by sending GGP information and waiting for a response, and then update the routing table if a response containing specific information is received.

 

Note that GGP's latest improvement, SPREAD, is already available on the Internet, but it's not as widespread as GGP. GGP is called Vector-Distance Protocol. To work effectively, a protocol converter gateway must contain complete information about all gateways on the Internet. Otherwise, computing an efficient route to a destination would be impossible. For this reason, all core gateways maintain a list of all core gateways on the Internet. This is a fairly small table that the gateway can easily handle.

 

 

The Exterior Gateway Protocol is used to transfer information between non-core adjacent protocol converter gateways. Non-core gateways contain the routing information of all the gateways directly adjacent to them on the Internet and their connected machines, but they do not contain the information of other protocol converter gateways on the Internet. For the vast majority of EGPs, only the local area network or wide area network information that maintains their services is restricted. This prevents excessive routing information from being transferred between the LAN or WAN. EGP enforces the exchange of routing information between non-core gateways.

 

Since the core protocol converter gateway uses GGP and the non-core gateway uses EGP, and both are used on the Internet, there must be some way for the two to communicate with each other. The Internet enables any autonomous (non-core) gateway to send "reachable" information to other systems, which must be sent to at least one core gateway. If there is a larger autonomous network, it is often assumed that there is a protocol converter gateway to handle this reachability information.

 

Like GGP, EGP uses a query process to make the protocol translator gateway aware of its neighbors and constantly exchange routing and state information with its neighbors. EGP is a state-driven protocol, which means that it relies on a state table that reflects the gateway's situation and a set of operations that must be performed when a state table entry changes.

 

 

There are several internal protocol converter gateway protocols available, the most popular are RIP and HELLO, another protocol is called Open Shortest Path First Protocol (OSPF), none of these protocols are dominant, but RIP is probably the most common the IGP protocol. The selection of a particular IGP is based on the network architecture. Both RIP and HELLO protocols calculate the distance to the destination, and their messages include the machine ID and the distance to the machine.

 

Generally, messages are long because their routing tables contain many entries. RIP and HELLO always maintain connectivity between adjacent gateways to ensure machines are active. Routing Information Protocol uses broadcast technology. It means that the protocol converter gateway broadcasts the routing table to other gateways at regular intervals. This is also a problem with RIP as it increases network traffic and reduces network performance. The HELLO protocol differs from RIP in that HELLO uses time rather than distance as a routing factor. This requires the protocol converter gateway to have reasonably accurate time information for each route. For this reason, the HELLO protocol relies on clock synchronization messages.

 

Open Shortest Path First is a protocol developed by the Internet Engineering Task Force in the hope that it will become the dominant IGP. Using "shortest path" to describe the routing process of a protocol is inaccurate. A better name is "optimal path", where many factors are considered to determine the best route to a destination.

 

 

A transport gateway is used to establish a transport connection between two networks. Using a transmission gateway, hosts on different networks can establish a cascaded, point-to-point transmission connection spanning multiple networks. For example, the commonly used router is the transmission gateway. The function of the "gateway" is reflected in the connection between two different network segments, or the connection between two different routing protocols, such as RIP, EIGRP, OSPF, BGP, etc.

 

 

The application gateway performs protocol conversion at the application layer. For example, if one host implements the ISO e-mail standard and the other host implements the Internet e-mail standard, if the two hosts need to exchange e-mail, they must go through an e-mail gateway for protocol conversion. This e-mail gateway is a Application Gateway. NCP is a protocol working on the seventh layer of OSI, which is used to control the interaction between the client station and the server, and mainly completes the functions of opening, closing and reading files in different ways.

 

 

The signaling gateway SG mainly completes the relay of signaling messages between No. 7 signaling network and the IP network. message, BSSAP message between 3G and 2G), and can also complete the transfer of ISUP messages between the MSC/GMSC of 2G and the soft switch.

 

Trunk gateways are also called IP gateways, and are VoIP devices that meet the needs of telecom operators and enterprises at the same time. The relay gateway (IP gateway) is constructed based on the relay board and the media gateway board. The single board can provide up to 128 channels of media conversion, two Ethernet ports, and the chassis adopts the industry-leading CPCI standard, which is easy to expand and has high stability, High reliability, high density, large capacity, etc.

 

The access gateway is a media access gateway for IP-based voice/fax services, providing efficient and high-quality voice services, and providing VoIP solutions for operators, enterprises, communities, and residential users.

 

 

6.2.1 Protocol Gateway

 

Protocol gateways usually do protocol conversion between network areas that use different protocols. This conversion process can take place at layers 2, 3 or between layers 2 and 3 of the OSI reference model. But there are two protocol gateways that do not provide translation capabilities: security gateways and pipes. Due to the logical differences between two interconnected network areas, a security gateway is a necessary intermediary between two technically similar network areas. Such as private wide area network and public Internet.

 

6.2.2 Application Gateway

 

An application gateway is a system that translates data between different data formats. A typical application gateway takes input in one format, translates it, and sends it in a new format. Input and output interfaces can be separate or use the same network connection.

 

Application gateways can also be used to connect LAN clients to external data sources, providing local hosts with connections to remote interactive applications. Placing the application's logic and execution code on the local area network client side avoids the disadvantages of low bandwidth, high latency wide area networks, which results in faster client response times. The application gateway sends the request to the corresponding computer, obtains the data, and converts the data format into the format required by the client if necessary.

 

6.2.3 Security Gateway

 

Security gateways are an interesting fusion of technologies with important and unique protections ranging from protocol-level filtering to very sophisticated application-level filtering.

 

It can be said that a gateway is a computer system or device that acts as a switching task. A gateway is a translator between two systems using different communication protocols, data formats or languages, or even completely different architectures. Unlike bridges that simply communicate information, gateways repackage the received information to suit the needs of the destination system. At the same time, the gateway can also provide filtering and security functions. Most gateways operate on the top layer of the OSI 7 layer protocol - the application layer.

 

 

The current IPV4 IP address is 32-bit, and is divided into three types of addresses: A, B, and C according to the first few digits; but due to the rapid development of the Internet, IP resources are increasingly exhausted, and there are fewer and fewer IP sites available for allocation. There is a serious conflict with the rapid development of the Internet. When IPV6 is far from being fully upgraded, the only way to access the Internet is to use a proxy server to convert the intranet address and the public network address.

 

The intermediary proxy server is a gateway, that is, the gateway brings endless troubles to the current multimedia communication system. In the case of poor IP resources, the only way to access the broadband network is to use a gateway or even a multi-layer gateway, because the multimedia communication system protocols such as H.323 and other parties who want to conduct business must have an IP address of the public network, and broadband has an IP address. How many users can meet this requirement? Microsoft's NETMEETING and other multimedia communication systems are in such an awkward position; cross-gateway becomes a headache.

 

Cross-gateway: Network data passes through layer-by-layer gateways, subject to the speed of gateway nodes, and the network speed is greatly reduced. Based on the underlying network protocol, the cross-gateway technology breaks through the bottleneck of the gateway and realizes point-to-point communication between customers.

 

 

The main functions of the gateway: Gateway (Gateway), also known as the Internet connector, protocol converter. The gateway is on the transport layer to realize network interconnection and is the most complex network interconnection device. Gateways can be used for both WAN interconnection and LAN interconnection.

 

Gateway main specifications and parameters:

 

Main interface type of security gateway: RJ45 main interface number: 3 ports.

 

Main parameters: Supported protocols: TCP/IP protocol, ICMP protocol, RIPv2 protocol, static routing protocol, dynamic routing protocol, PAP protocol, CHAP protocol, NAT protocol, PPPoE protocol, 250K concurrent sessions, new sessions 7K/sec, Firewall performance 120Mbps, 40G hard disk, 100 VPN tunnels, 3DES encryption performance 30Mbps, virus mail scanning 25000/hour, spam 15000/hour, HTTP scanning 1MB/S; built-in firewall.

 

The selection points of the protocol converter gateway and the main technical conditions for ordering:

 

A gateway is a device that connects two network segments using different protocols. Its function is to translate and convert the data using the transmission protocol in the two network segments. For example, an enterprise intranet often needs to send e-mails to relevant addresses on the Internet through the gateway.

 

8.1 Gateway is highly scalable

8.2 The gateway can support multi-protocol, can scan SMTP, HTTP, FTP and POP3 communication, and has the protection function for the network and users.

8.3 The gateway can transparently scan online and save information such as source IP and MAC address. The transparent scanning option allows you to protect your internal web server while being easy to install.

8.4 The gateway enables content management to prevent users from receiving or sending emails with certain types of attachments, oversized emails, or emails with too many or too large attachments.

8.5 Detection of spam and anti-relay.

8.6 The main technical conditions of gateway ordering can meet the network interconnection of different communication protocols, so that files can be transmitted between these networks, preventing hacker intrusion, checking viruses, identity authentication and authority checking and many other security functions. Collaborate with related products.

8.7 The gateway in the main room should be able to be installed in the main cabinet.

 

 

For specific construction methods, please refer to the national architectural standard design atlas "Smart Home Control System Construction Atlas 03X602" and the international standard specification "EIA/TIA569 Commercial Building Communication Channel and Space Standard".