Email architecture in Intranet/Internet platforms

I. Overview of the Intranet/Internet platform

, The dotted line below is the Internet, which provides Web Services, DB services, DNS services, exchange services, and so on; The above is the Intranet, which provides services similar to the Internet. This article focuses on the mail system under this structure.

Ii. Architecture of email on the Intranet platform

Email Service is an application built on the network infrastructure. Exchange on NT, Group Wise of Novell.

Establish a network environment. The following describes the exchange mail system under NT. There is a delegate relationship in NT. A delegated relationship is used to establish a connection between a domain and a domain. It can perform cross-domain traffic confirmation. After authorization, you only need to have an account in a domain to access resources in other domains in the network. It is generally called a trusted domain and a entrusted domain. First, let's talk about the exchange structure, then the mail structure of a single post office, and finally how to use connectors in NT to construct an intranet mail system.

1. Exchange Server Components

The structure of the Exchange Server is based on components. These components work together to provide the foundation for information delivery and add connections

Add parts to the external system. The two connection components are as follows:

(1) Core Components of Exchange Server:

System Basics: This part maintains information services by executing the following four functions.

A. Create an email address and directory for the new user.

B. If a directory task is deleted, the space is recalculated.

C. Create a route table on the site

D. Maintain Information Tracking logs

Directory Service: Its functions are as follows:

A. contains the address, email address, public folder, partition table, and configuration information about the site and service.

B. Maintain the directory information of all servers on a site and automatically copy the information.

Information Transmission proxy (MTA ):

A. Submit, transfer, and route information to exchange MTA, external x.400 MTA, or Microsoft Mail Connector.

B. Expand the Partition Table of route information.

Information Storage: It stores server-based Mail Information and other information. Two databases (public information storage and private

Personnel Information Storage) to maintain information.

(2) additional parts of the Exchange Server (only available ):

Internet Mail Server: Exchange uses Internet mail server to connect to SMTP systems (such as Internet

). It can also be used to connect to other exchange systems. The POP3 client can use the Internet mail server to submit emails.

Directory synchronization: it is information-based and depends on Microsoft's Mail Connector.

Lotus cc: Mail Connector

Idle/busy Connector

(3) Email users: four types of applications

Most of the work of the exchange administrator is to create and manage users. user applications include mailbox, partition table, Custom User,

Public folder.

Mailbox: the Administrator creates a mailbox for each user. The mailbox is the physical location of the email to be sent on the Exchange Server computer.

Location.

Partition Table: When a partition table is created, a user can send emails to a group of users.

Customized users: allows users to communicate with external sites

Public Folder: its information can be shared among many different users.

2. Mail System of a single post office in an Enterprise

Many email systems are Client/Server structures. The system administrator sets the user attributes on the Information Exchange Server.

Is connected to the end users. There are many email system software, such as Microsoft Exchange and Netscape Navigator. However, most of them are similar in nature. If you have installed an email server on an NT domain, the domain user must be equipped with the necessary client software (no matter what client software you choose, the configuration of the domain user mainly includes two: first, set the email server name or IP address, and second, set the email address ). It is easier to send emails to each other.

Select exchange as the email server and install it on the NT (IP Address: 172.220.62.8) server; Internet

Outlook Express in iise 4.0 is installed on Windows 95 client as the mail client. If the client user name is liuli and the domain name is xxzx. CNCN, the server needs to create a new user liuli and create a new mailbox for the user. For convenience, the mailbox name is also called liuli. The client configuration is as follows:

(1) Start Internet ipve

(2) Go to the selected email

(3) Configure

A. Display name: liuli

B. Email Address: liuli@xxzx.cncn

C. receiving email server: POP3

POP3 server: 172.220.62.8

SMTP server: 172.220.62.8

D. logon method:

POP3 Account name: liuli

E. Internet mail account name: 172.220.62.8

F. In this example, connect to the local area network (LAN.

If there are several machines in the Bureau's network, create the necessary number of mailboxes on the NT, and configure each client accordingly.

You can send emails to each other.

3. Using connectors to construct an intranet mail system

(1) Use the exchange site connector on two mutually trusted NT domains to connect messages in two domains to all exchange connectors, the establishment and management of site connectors are the fastest and simplest. It uses remote process calls defined by the "Open System Foundation" (OSF) to transmit messages, directories, and folder copies between exchange sites.

The site connector saves a list of target servers for a remote site. Any MTA of the local site can select a target server from the list.

Server and send information to it.

Site connector <-------------- RPC --------------> site Connector

Site A: Exchange Server (is1) Site B: Exchange Server (is2)

Is the site connection diagram. The site planning table is listed below.

Site planning table

Site	A	B
Server	Is1	Is2
Account name	Org	Gov
Site address	172.220.62.8	172.10.10.17

Both Site A and site B are in the same organization and the organization name is MTB. Users of Station A and Station B send emails to each other on the following conditions:

Two-way trust is established between the two NT domains of Station A, Station A, and Station B. The purpose is that users in one domain can access resources in another domain.

B. Create required cross-site Permissions

C. Establish a site-to-site connection

D. create directory replication between sites

(2) Use the site connector of exchange to connect emails in two untrusted NT domains

For example, the Exchange Server S1 is installed on the NT domain D1, and the Exchange Server S2 is installed on the NT domain D2. If the S1 is installed, the S2 is not yet installed. Follow these steps to connect emails.

A. Find the NT account of the installation S1, which is assumed to be xserver.

B. Create an account xserver on D2 with the same password as the xserver on d1. Use xserve for additional installation on D2

Exchange.

C. Grant the "Access Computer From Network" user permissions to the two nt accounts.

D. After installation, configure the site connector on the main feature page.

(3) using the DNS function in NT to establish a mail system for multiple post offices in an enterprise intranet

First, explain the DNS in NT.

The solution for host name and IP address is as follows:

Domain Name System (DNS) is widely used in the Internet. When a DNS workstation initiates an IP address query request, the database on the DNS server can provide the required data, it has three query modes in total:

A. recursive query

After the DNS workstation sends a query request, the DNS server must notify the DNS workstation of the correct data or notify the DNS workstation that it cannot be found.

Required data. The DNS server does not provide the address of another DNS server on the DNS workstation. The DNS workstation is required to query the server on its own. The query request initiated by the DNS workstation belongs to this type of query.

B. Forwarding Query

After the DNS workstation sends a query request, if the DNS server does not contain the required data, it will tell the DNS workstation another

The IP address of the DNS server, which is automatically queried by the DNS workstation until the required data is found. If no data is required in the last DNS server, the DNS workstation query fails. The query request between the DNS server and the DNS server is a forwarding query.

C. Reverse Query

Reverse query allows the DNS workstation to query its name by IP address.

The following example shows how to configure the configuration.

Is the case of two domains (if there are other domains, the situation is similar ).

In, there are two domains: xxzx.com.cn and jg.com.cn. Their DNS servers are is1 and is2. DNS workstations are A1, A2 ,...... An, B1, B2 ,...... BM. If the domain xxzx.com.cn and the domain jg.com.cn provide Web Services and FTP services, the server ISD can decide whether to provide domain name resolution for such servers as needed.

For domain name resolution, the computer in the domain xxzx.com.cn must configure as follows (the domain jg.com.cn configuration is similar ).

Workstation A1 (A2 ,...... An configuration is similar:

If TCP/IP is installed properly, set the DNS in TCP/IP

Host Name: A1

Domain: xxzx.com.cn

DNS server search order: 172.220.62.8

Configuration of server:

Set the IP address and DNS in TCP/IP if TCP/IP is installed properly.

IP: 172.220.62.8

Host Name: is1

Domain: xxzx.com.cn

DNS server search order: 172.220.62.8

Assume that the DNS server has been installed in server A as follows:

A. Choose "Administrative Tools> DNS Manager> DNS> new server", add the DNS server to be managed, and enter its

Host Name (is1.xxzx.com.cn) or IP address (172.220.62.8)

B. Create a new region xxzx.com.cn with the region type as the primary region under 172.220.62.8.

To view three SOA records, NS (Name Server) records, and a Host record.

C. DNS workstation A1, A2 ,...... An host record is added to the domain

Xxzx.com.cn.

D. Select "use forwarder ISD" under DNS properties and enter the IP address of ISD.

Three points in implementing DNS:

A. the DNS server itself has the role of a DNS workstation. The server is1 and is2 must also be in the TCP/IP attribute as the DNS workstation.

.

B. For example, DNS workstation B1 is a WWW, FTP, or other server. To enable access to DNS workstation A1.

Add a host record B1 to the DNS server ISD. After the A1 workstation sends a query request (such as ping b1.jg.com.cn), is1 searches for its DNS File Based on the DNS attribute in A1's TCP/IP. The DNS file does not contain the required data, therefore, the DNS server is configured to use the forwarder ISD, so it will tell the DNS workstation A1 the IP address of another DNS server ISD. A1 will automatically query the ISD server, and the query result is obtained here. If no, whether the server is set as a backup server based on another attribute of server is1. If yes, it is completely dependent on ISD and notifies the DNS workstation A1 That the query fails. Otherwise, the query continues. After finding the IP address, find the server to be accessed Based on the routing protocol (such as rip in NT) and access the server. Another way for workstation A1 to access B1 is that the DNS server is1 does not use the DNS server ISD as the forwarder, but selects the DNS server is2 as the forwarder to enable A1 to access B1.

C. recursive query is set in the DNS under the TCP/IP attribute, and forwarding query is set in the DNS server, for example, xxzx.com.cn

For reverse query, you need to create a region named 220.172.in-ADDR. Arpa, and create an associated PTR record when creating the Host record.

It is a cross-post office scenario.

In, the N users of Site A and m users of Site B want to send emails to each other. Mail Server A can be seen as post office A, mail

Server B can be seen as a post office B. To send emails to each other, You need to configure the following:

The following is the configuration of Site:

IP: 172.220.62.8

Domain Name: xxzx. CNCN

Configurations on DNS:

Is1.xxzx. CNCN. In a 172.220.62.8

JG. CNCN. In mx10 is2.jg. CNCN

The configuration of Site B is similar to that of Site.

IP: 172.100.16.6

Domain Name: JG. CNCN

Configurations on DNS:

Is2.jg. CNCN. In a 172.100.16.6

Xxzx. CNCN. In mx10 is1.xxzx. CNCN

Is2.jg. CNCN. ina172.100.16.6 is an address record, or a record for short. There is also an MX record above. This record

Description, with the domain address xxzx. emails associated with CNCN should be sent to the host is1.xxzx. CNCN, in indicates that this is an Internet record, and number 10 indicates the priority value. If there are multiple MX records for emails in the specified domain, the transmission SMTP server will first transmit the mail to the host with the lowest numeric value.

If there are several nt lan in the enterprise intranet and each bureau has at least one email server on the Internet, follow the settings above

Planning and setting, online users can send emails to each other.

Iii. Architecture of email in Intranet/Internet platforms

In fact, to build an intranet, you must first assign the correct IP address, determine the domain name, then perform domain name resolution, and finally construct the mail

Component System. Here we will introduce the IP address.

Each 32-bit IP address is divided into networkid and hostid, and can only be one of the five formats from Class A to Class E.

Class A: designed for large networks with many hosts. bit0 = 0 indicates class A address, bit1 ~ Bit7 indicates network, bit8 ~ Bit31 table

Displays the host. Only seven network IDs are available. Only 128 Class A addresses are available, of which 0 and 127 are reserved. Class A starts from 1 ~ Starting from 126.

Class B: Most units with distributed processing systems (including many lan and hosts) use Class B, and Class B addresses start with two

10 (Binary) indicates that the last 14 digits indicate the network, the remaining 16 digits indicate the host, and the host addresses 0 and 65535 are reserved. Class B takes 128 ~ 191.

Class C: generally used on small networks, such as local networks. Class C starts with 110, and the last 21 bits indicate the network, the remaining 8 bits indicate the host, and the master

The address 0 and 255 are retained. Class C starts with 192 ~ 223.

Class D: It starts with binary 1110 and is mainly used for broadcast. Class D starts from 224 ~ 254.

Class E: It starts with binary 1111 and is reserved for future use.

Due to the prevalence of LAN, the Internet management organization modifies the IP address structure, and the new structure allows additional

In this way, the format of the network and host is changed to the format of the network, subnet, and host. The subdomain space comes from the Space reduced by the host domain.

For ease of understanding, explain broadcast first. A broadcast is a packet sent to multiple hosts, both at the data link layer and at the network layer.

Generate broadcast. Data link layer broadcast sends data packets to all hosts connected to a specific physical network. Network Layer broadcast sends data packets to all hosts connected to a specific logical network. TCP/IP supports three types of broadcast packets:

Full 1 Broadcast: by setting the broadcast address to full 1 (broadcast bandwidth 255.255), all hosts on the network can receive the broadcast.

Network Broadcast: sets the network part of the IP address as a specific network number, and the host part as full 1.

All hosts on the specified network can receive broadcasts.

Subnet broadcast: sets the network part of the IP address to a specific network number, the subnet part to a specific subnet number, and the specified subnet

The host on can receive the broadcast.

Some addresses are reserved for broadcasting and some special requirements on behalf of this website:

Net = 0, host = 0 this machine is on this network

Net = 0, host = H specific host h on this network

Net = all ones, host = all ones limited range Broadcast

Net = N, host = all ones directly broadcast to the network

Net = N, sub = all ones, host = all ones directly broadcast to all subnets on N

Net = N, sub = s, host = all ones directly broadcast to all hosts in the N network, s Subnet

Net = 127, host = any Internet host loopback self-check address

The following uses Class B addresses as an example to list subnet masks:

Subnet Mask	Number of subnets	Number of hosts
201710000128.0	----	----
201710000192.0	2	16382
201710000224.0	6	8190
255.255.240.0	14	4094
201710000248.0	30	2046
255.255.252.0	62	1022
255.255.254.0	126	510
255.255.255.0	254	254

For example, the subnet mask 255.255.240.0 can divide Class B addresses ranging from 150.100.0.0 to 150.100.255.255

16 subnets: 150.100.0.0 ~ 150.100.15.255, 150.100.16.0 ~ 150.100.31.255, 150.100.32.0 ~ 150.100.47.255 ,...... 150.100.192.0 ~ 150.100.207.255, 150.100.208.0 150.100.223.255, 150.100.224.0 ~ 150.100.239.255, 150.100.240.255 ~ 150.100.0000255. The first address (network ID) and the last address (broadcast address) of each subnet are reserved addresses, for example, the subnet 150.100.192.0 ~ In the address 150.100.207.255, 150.100.192.0 is the network ID, representing this subnet. 150.100.207.255 is the broadcast address. Because 150.100.0.0 is both 150.100.0.0 ~ The network ID of 150.100.15.255 is another type of B network: 150.100.0.0 ~ 150.100.0000255, 150.100.0000255 is both 150.100.240.0 ~ The broadcast address of 150.100.0000255, which is another type of B network: 150.100.0.0 ~ The broadcast address of 150.100.255.255, so the subnet is 150.100.0.0 ~ 150.100.15.255 and 150.100.240.0 ~ 150.100.0000255 is unavailable. The actual available address from 150.100.0.0 to 150.100.0000255 is 14*(16*256 ?) = 57336. Originally, a Class B network number has 65534 network addresses. Due to the division of subnets, some addresses are lost.

Run winipcfg in Windows 95 to view the adapter address, IP address, and subnet mask.

Based on the above principles, the author accurately calculates the IP address 204.96.37.21 assigned by the post office and the mask 255.255.255.252.

The IP address of the test router connected to the router is 204.96.37.22, which facilitates debugging.

If the Intranet has been built based on the IP address principle and DNS nature, and the intranet mail system has also been built, how can we construct the email system on the Intranet/Internet platform?

In exchange, there is a part of IMS, which provides the foundation for us to build an email system on the Intranet/Internet platform.

IMS (Internet Mail Server) is a component integrated in exchange. It uses SMTP, TCP/IP, and DNS

Or directly route information to another SMTP host. SMTP is a protocol that defines the process of sending mail between two computers. It defines the format and method of the information to be sent. SMTP provides a connection-based transfer protocol forwarding mechanism like TCP/IP. To use IMS, you must Configure TCP/IP on the Exchange Server computer. TCP/IP and SMTP work together to provide information connection to other SMTP hosts or the Internet.

In, the 172.220 network is Intranet, and the 206.96.24 network is Internet. The two parts are connected through the proxy server.

Describes the process of sending emails to each other.

The process of Internet mail arriving on the Intranet:

1. The domain name 206.96.24 has been registered and is a legal domain name (resolution provided in the Internet Domain Name System ).

There is a DNS server and an email server. Users in this domain can send emails to other users on the Internet.

2. If the domain name is an intranet domain name, the DNS server on the external network (206.96.24) will resolve the email and send it to the external network.

The email server on the Internet.

3. the email server on the external network classifies emails by domain name after receiving the emails, and delivers the emails on the Intranet to the email server on the Intranet.

Server.

4. The intranet email server processes the received emails.

The process of Intranet emails arriving at Internet:

This process is relatively simple. The email server classifies the emails to be sent, and transfers all emails with domain names not on the Intranet to the external network.

On the email server of the local network, it is processed by the email server on the external network.