Linux Server Setup Guide-proxy access server (4)

Article Title: Linux Server Setup Guide-proxy access server (4 ). Linux is a technology channel of the IT lab in China. Includes basic categories such as desktop applications, Linux system management, kernel research, embedded systems, and open source.
　　 Section 7 ISDN dialing
& Amp; 7.1 Introduction
Over the past two years, ISDN has been booming in China, and the telecom departments of various provinces and cities have successively activated ISDN services. Particularly in Shanghai, Guangzhou, Fuzhou, and Beijing, the trend of ISDN development is even more unstoppable. In Shanghai, by May this year, the number of ISDN users had reached 32,000. With its fast connection speed and high transmission quality, ISDN is attracting more and more users.
　　
What is ISDN?
　　
ISDN is short for the integrated business digital network, which is developed by the Integrated telephone Digital Network (IDN. ISDN is a combination of digital exchange and digital transmission. It provides existing services in various communication networks in a rapid, accurate, economic, and effective manner, and integrates communication and data processing, it has created many new businesses unprecedented. ISDN is a fully digital network. In other words, no matter whether the original signal is voice, text, data, or image, it can be converted to a digital signal and transmitted in the ISDN network. In the traditional telephone network, the network is digitalized, but analog transmission is still used between users and telephone bureaus, which is prone to distortion due to the accumulation of Noise along the way. For ISDN, the user line is digitalized, end-to-end digital connection is provided, and the transmission quality is greatly improved.
As ISDN implements end-to-end digital connections, it can support various services, such as voice, data, and images. As electronic communication continues to expand globally, many of us need to exchange information with users in different regions. Nowadays, communication requires not only simple sound exchange, but also sharing different information in various formats. For example, some people need high-speed data and file transmission, some may need multimedia and conference television, and some may want to access the central database. The service of ISDN covers all services of the existing communication network, such as fax, telephone, visual text, monitoring, email, visual phone, conference and television, and can meet the needs of different users. Another basic feature of ISDN is to provide users with standard inbound interfaces. You can combine terminals of different business types, connect to the same interface, and change the terminal type at any time.
There are two main types of ISDN: basic rate (BRI) and basic group rate (PRI ). All interfaces provided by the Telecommunications Board to common users are BRI interfaces. The original twisted pair wires can be used at a rate of 144Kb/s. BRIISDN can provide two B channels (64 K each) and one D channel (16 K) on a pair of twisted pair wires. Channel D is used to transmit signaling, and channel B is used to transmit voice and data. One phone only occupies one channel B. Therefore, multiple services or conversations are performed simultaneously. The PRI interface speed is 2.048 Mb/s, which is used for applications that need to transmit a large amount of data, such as PBX and LAN interconnection.
　　
What can ISDN do?
　　
ISDN can provide users with a variety of services. Currently, CCITT classifies ISDN services into three types: bearer services, user terminal services, and supplementary services.
The bearer service is an information transmission service provided by the ISDN network. It provides information transmission between users without changing the information content. Common bearer services include: voice service, 3.1KHz audio service, and unlimited 64 K digital service. Generally, the voice service is used for telephone calls. This type of bearer service indicates to the network that the current user is making a call, and the network can perform voice compression, Echo elimination, and digital voice insertion. The 3.1KHz audio bearer service is mainly used for data transmission using a modem or analog Fax. Such services can perform digital-analog conversion on signals in the network, however, other forms of voice processing technology must be disabled. If you want to use ISDN for dial-up Internet access, you need to use a 64 K unlimited digital service. In this case, the network does not process the transmitted data. Sometimes, if a user encounters a situation where the requested ISDN line can call but cannot access the Internet through dialing, it may be caused by the fact that the line is open for a non-limited 64 k Data bearer service.
User Terminal business refers to all user-oriented application businesses. It includes network functions and terminal device functions. Users can use telephone, four types of fax, data transmission, conference and television, and other user terminal services, but all need terminal equipment support.
Supplementary Services are additional services provided by the ISDN network on the basis of services and user terminal services. The purpose is to provide users with more convenient services. Currently, the Shanghai Telecom Bureau provides the following supplementary services to users: multi-user numbers, sub-addresses, caller ID Display, call waiting, and call persistence. In addition to the insufficient number resources of multiple users, you must pay a certain fee each month. Other supplementary services are provided free of charge. Of course, you must first apply for these services from the Telecommunications Bureau. These services can bring great convenience to users. For example, the call wait service allows you to call an external call when two calls are used simultaneously. Call Persistence means that when you make a call, you can temporarily suspend the existing call to make a new call or receive other calls. After the call is completed, the original call will be restored.
　　
Why ISDN?
　　
Both individuals and companies, ISDN should be your first choice. Because it has the following benefits:
　　
Low Price:
　　
Because a single network provides different services, ISDN greatly improves the utilization of network resources. You do not need to purchase different devices and lines to access different networks. As far as Shanghai is concerned, the telecom Bureau has launched a large ISDN discount package for users. It only costs 490 yuan to get the smart network terminal and ISDN adapter produced by Shanghai Bell, the original analog phones and fax machines in the home can be directly connected. With the ISDN adapter, you can access the Internet at a rate of kb/s. The cost is less than the price of a 56 K modem. In addition, the monthly rental fee of each ISDN line is 24 yuan, which is the same as that of a simulated telephone line, but can be used as two analog lines. Why not?
　　
High-speed data transmission:
　　
With ISDN, the maximum data transmission rate is kb/s, which is several times higher than the data rate in the existing telephone network. For Internet users, when using a 56 K modem, the file download speed is about 4 kb/s at the fastest speed, but also depends on the network situation. If two B channels are used at the same time, the download speed is up to 12 kb/s, which is three times faster! In this way, the cost of time, telephone and Internet access is considerable.
　　
High transmission quality:
　　
Users who frequently access the Internet must have similar experience. Sometimes it takes several hours to download a large file. After the download, they find that the downloaded file is unavailable due to poor line quality and high error rate. However, this problem rarely occurs when you use ISDN. Because ISDN uses an end-to-end digital connection, the transmission quality is high and it will not be affected by static electricity and noise like analog lines. In addition, as digital devices in ISDN facilitate fault detection, the system reliability is also improved.
　　
Flexible and convenient:
　　
ISDN provides various services. Users only need one inbound interface to use various services provided by the network. For example, you can connect your phone and personal computer to ISDN and make a phone call while accessing the Internet. You can also access devices such as videophone, conference TV, and ISDN Router. Because these devices have corresponding international standards, they can be as portable as household appliances, and can be pulled from one outlet to another.
In general, ISDN is a very mature technology that will surely bring you into a brand new digital age at its high-quality service and civilian price.
　　
& Amp; 7.2 built-in ISDN card
The installation of the built-in ISDN card is troublesome. The main cause of this situation is that there are many card models and the kernel supports a limited range, I recommend several types of products from Shanghai Bell. We only need to re-compile the kernel and add the ISDN model.
　　
& 7.2.1 Configuration
　　
1. Kernel configuration file
　　
Instance:
The following are the options we need. Because all Chinese Linux distributions on the market do not support built-in ISDN, we have to do it ourselves.
Run make menuconfig in the/usr/src/linux directory, and then select the options in the ISDN item:
<*> ISDN support
[*] Support synchronous PPP
[*] Use VJ-compression with synchronous PPP
[*] Support generic MP (RFC 1717)
[*] Support audio via ISDN
HiSax unzip enschipset driver support
[*] HiSax Support for EURO/DSS1
[*] Support for german chargeinfo
[*] Disable sending complete
[*] Disable sending low layer compatibility
[*] HiSax Support for Teles 16.3 or PNP or PCMCIA
[*] HiSax Support for Winbond W6692 based cards
Then save the disk and exit. Execute make dep, make clean, make bzImage, make modules, make modules_install, depmod? A, make install.
At this time, the new core has been generated, and our old core has not been deleted, but is backed up. If there is any problem, it can still be recovered. Finally, we need to restart to make the new kernel take effect.
　　
2. isdn4k-utils-3.1beta7_mini-1.i386.rpm
　　
This is a package that supports built-in ISDN. After the package is installed, the system will recognize our built-in card. Of course, in order to implement dialing, we also need to write a dialing script and the corresponding hanging script, which are isdnon and isdnstop.
　　
3. isdnon
　　
Instance:
#! /Bin/sh
Echo-n E>/dev/ttyS1
Modprobe hisax type = 36 protocol = 2
Echo 1>/proc/sys/net/ipv4/ip_dynaddr
# Kill previous ipppd process
If [-r/var/run/ipppd. ippp0.pid]
Then kill-9 'cat/var/run/ipppd. ippp0.pid'
Fi
If [-r/var/run/ipppd. ippp1.pid]
Then kill-9 'cat/var/run/ipppd. ippp1.pid'
Fi
# Variables
MYIP = 0.0.0.0
REMIP = 0.0.0.0
My MSN = 62986638
REMMSN = 169
Myuser= 169
REMNAME = 169.
# Init
/Sbin/isdnctrl verbose 3
#/Sbin/isdnlog-sS-v1-m0x17d7-l0x3d7-C/dev/console-D/dev/isdnctrl
# Add and set ippp0
/Sbin/isdnctrl system on
/Sbin/isdnctrl addif ippp0
/Sbin/isdnctrl eaz ippp0 $ MYMSN
/Sbin/isdnctrl addphone ippp0 out $ REMMSN
/Sbin/isdnctrl huptimeout ippp0 3600
/Sbin/isdnctrl l2_prot ippp0 hdlc
/Sbin/isdnctrl l3_prot ippp0 trans
/Sbin/isdnctrl encap ippp0 syncppp
/Sbin/isdnctrl dialmode ippp0 auto
# Add and set ippp1
/Sbin/isdnctrl addslave ippp0 ippp1
/Sbin/isdnctrl eaz ippp1 $ MYMSN
/Sbin/isdnctrl addphone ippp1 out $ REMMSN
/Sbin/isdnctrl huptimeout ippp1 3600
/Sbin/isdnctrl l2_prot ippp1 hdlc
/Sbin/isdnctrl l3_prot ippp1 trans
/Sbin/isdnctrl encap ippp1 syncppp
/Sbin/isdnctrl dialmode