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Network services and network services. Internet Provider Contemporary Network Service (CCS) Network Services of Remote Management Resources Information Systems

And the server port, resulting in a compound that allows you to interact to two computers using the corresponding application-level network protocol.

Porter numbers

The port number for "binding" services is selected depending on its functional purpose. For assigning port numbers to certain network services is replied by IANA. The port numbers are in the range of 0 - 65535 and divided into 3 categories:

Porter numbers	Category	Description
0 - 1023	Well-known ports	The port numbers are assigned to IANA and in most systems can be used exclusively by the system (or ROOT user) or application programs running privileged users. Should not be used without registration IANA. The registration procedure is defined in section 19.9 RFC 4340 (English).
1024 - 49151	Registered ports	The port numbers are included in the IANA directory and in most systems can be used by the processes of ordinary users or programs running ordinary users. Should not be used without registration IANA. The registration procedure is defined in section 19.9 RFC 4340.
49152 - 65535	Dynamically used ports and / or ports used inside closed (Private) networks	Designed for temporary use - as client ports, ports used in coordination for private services, as well as for testing applications before registering dedicated ports. These ports can not be registered .

Compliance list between network services and port numbers

The official list of conformity between network services and port numbers is conducted by IANA.

History of conformity regulation

The unification of network services compliance with socket numbers (ports) rose in RFC 322 and 349, the first regulation attempts were taken by John bed in RFC 433 and 503.

Actual list

netstat -an.

In the Windows OS OS, the result of this command looks like this:

Active Connections Name Local Address External Address TCP Condition 0.0.0.0:135 0.0.0.0.0: Listening TCP 0.0.0.0:445 0.0.0.0: Listening TCP 127.0.0.1:1026 0.0.0.0: Listening TCP 127.0.0.1:12025 0.0.0.0: Listening TCP 127.0.0.1:12080 0.0.0.0: Listening TCP 127.0.0.1:12110 0.0.0.0: Listening TCP 127.0.0.1:12119 0.0.0.0: Listening TCP 127.0.0.1:12143 0.0. 0.0: 0 Listening TCP 192.168.0.16:139 0.0.0.0: Listening TCP 192.168.0.16:1572 213.180.204.20:80 Close_Wait TCP 192.168.0.16:1573 213.180.204.35:80 Established UDP 0.0.0.0:445 *: * UDP 0.0.0.0:500 *: * UDP 0.0.0.0:1025 *: * UDP 0.0.0.0:1056 *: * UDP 0.0.0.0:1057 *: * UDP 0.0.0.0:1066 *: * UDP 0.0.0.0:4500 *: * UDP 127.0.0.1:123 *: * UDP 127.0.0.1:1900 *: * UDP 192.168.0.16:123 *: * UDP 192.168.0.16:137 *: * UDP 192.168.0.16:138 *: * UDP 192.168 .0.16: 1900 *: *

In UNIX-like OS, the result of the team netstat -an. It has something like this:

Active Internet Connections (Servers and Established) Proto Recv-Q Send-Q Local Address Foreign Address State TCP 0 0.0.0.0.0:37 0.0.0.0:* Listen TCP 0 0 0.0.0.0:199 0.0.0:* Listen TCP 0 0.0.0.0.0:2601 0.0.0.0:* Listen TCP 0 0 0.0.0.0:3306 0.0.0.0:* Listen TCP 0 0 0.0.0.0:2604 0.0.0:* Listen TCP 0 0 0.0.0.0:2605 0.0. 0.0: * Listen TCP 0 0 0.0.0.0:13 0.0.0.0:* Listen TCP 0 0 0.0.0.0:179 0.0.0.0:* Listen TCP 0 0 0.0.0.0:21 0.0.0.0:* Listen TCP 0 0 0.0 .0.0: 22 0.0.0.0:* Listen TCP 0 0 0.0.0.0:1723 0.0.0.0:* Listen TCP 0 0 0 0.0.0.254:1723 10.0.0.243:2441 Established TCP 0 0 192.168.19.34:179 192.168.19.33: 33793 Established TCP 1 0 192.168.18.250:37 192.168.18.243:3723 Close_Wait TCP 0 0 0.0.0.0.254:1723 10.0.0.218:1066 Established TCP 1 0 192.168.18.250:37 192.168.18.243:2371 Close_Wait TCP 0 0 0 0.0.0.254 : 1723 10.0.0.201:4346 Established TCP 0 0 0 10.0.0.254:1723 10.0.0.30:2965 Established TCP 0 48 192.168.19.34:22 192.168.18.18:43645 Established TCP 0 0 0.0.0.254:38562 10.0.0.243:22 Establ Ished TCP 0 0 10.50.1.254:1723 10.50.1.2:5355 Established TCP 0 0 10.50.0.254:1723 10.50.0.174:1090 Established TCP 0 0 0 192.168.1254:1723 192.168.13.104:65535 ESTABLISHED TCP 0 0 0 0.0.0.254: 1723 10.0.0.144:65535 Established TCP 0 0 0.0.0.254:1723 10.0.0.169:2607 Established TCP 0 0 0 0.0.0.254:1723 10.0.0.205:1034 Established UDP 0 0 0.0.0.0:1812 0.0.0.0:* UDP 0 0.0.0.0.0:1813 0.0.0.0:* UDP 0 0 0.0.0.0:161 0.0.0.0:* UDP 0 0 0.0.0.0:323 0.0.0.0:* UDP 0 0 0.0.0.0:123 0.0.0.0:* RAW 0 0 192.168.10.254:47 192.168.13.104:* 1 RAW 0 0 10.0.0.254:47 10.0.0.120:* 1 RAW 0 10 10.10.204.20:47 10.10.16.110:* 1 Raw 0 0 192.168.10.254:47 192.168.11.72:* 1 RAW 0 0 10.0.0.254:47 10.0.0.144:* 1 RAW 0 0 10.0.0.254:47 10.0.0.205:* 1 RAW 0 0 10.50.0.254:47 10.50.0.174:* 1 RAW 0 0.0.0.0.254:47 10.0.0.170:* 1 RAW 0 0 0 10.0.0.254:47 10.0.0.179:* 1

Status (State) Listening Shows passively open connections ("Listening" sockets). They are them providing network services. Established - These are installed connections, that is, network services in the process of their use.

Check availability of network services

In case of detection of problems with a network service, various diagnostic tools are used to verify its availability, depending on their presence in this OS.

One of the most convenient means - the TCPTraceroute command (Traceroute variety), which uses TCP-Opening Opening Packs Connection (SYN | ACK) with the specified service (by default - WEB server, port 80) of the host and shows the information about the time of passage This type of TCP -Pakes through routers, as well as information about the availability of the service in the host of interest, or, in case of problems with the delivery of packages, in which location they arose.

Alternatively, you can use separately

traceroute for diagnosing packet delivery route (disadvantage - Using UDP-Pakes for diagnostics) and
telnet or Netcat to the port of the problem service to check its response.

Notes

Links

RFC 322 (eng.) WELL KNOWN Socket Numbers
RFC 349 (eng.) Proposed Standard Socket Numbers (canceled RFC 433)
RFC 433 (eng.) Socket Number List (canceled RFC 503)
RFC 503 (eng.) Socket Number List (canceled RFC 739)
RFC 739 (eng.) Assigned Numbers (The first list of assigned numbers was replaced by RFCs, the last of which RFC 1700)
RFC 768 (eng.) User Datagram Protocol
RFC 793 (eng.) Transmission Control Protocol
RFC 1700 (eng.) Assigned Numbers (The last list of assigned numbers is canceled RFC 3232)
RFC 3232 (eng.) Assigned Numbers: RFC 1700 IS Replaced by An On-Line Database
RFC 4340 (eng.) Datagram Congestion Control Protocol (DCCP) - Proposed Standard

Wikimedia Foundation. 2010.

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And the server port, resulting in a compound that allows you to interact to two computers using the corresponding application-level network protocol.

Porter numbers

Porter numbers	Category	Description
0 - 1023	Well-known ports	The port numbers are assigned to IANA and in most systems can be used exclusively by the system (or ROOT user) or application programs running privileged users. Should not be used without registration IANA. The registration procedure is defined in section 19.9 RFC 4340 (English).
1024 - 49151	Registered ports	The port numbers are included in the IANA directory and in most systems can be used by the processes of ordinary users or programs running ordinary users. Should not be used without registration IANA. The registration procedure is defined in section 19.9 RFC 4340.
49152 - 65535	Dynamically used ports and / or ports used inside closed (Private) networks	Designed for temporary use - as client ports, ports used in coordination for private services, as well as for testing applications before registering dedicated ports. These ports can not be registered .

Compliance list between network services and port numbers

The official list of conformity between network services and port numbers is conducted by IANA.

History of conformity regulation

The unification of network services compliance with socket numbers (ports) rose in RFC 322 and 349, the first regulation attempts were taken by John bed in RFC 433 and 503.

Actual list

netstat -an.

In the Windows OS OS, the result of this command looks like this:

In UNIX-like OS, the result of the team netstat -an. It has something like this:

Check availability of network services

In case of detection of problems with a network service, various diagnostic tools are used to verify its availability, depending on their presence in this OS.

Alternatively, you can use separately

traceroute for diagnosing packet delivery route (disadvantage - Using UDP-Pakes for diagnostics) and
telnet or Netcat to the port of the problem service to check its response.

Notes

Links

RFC 322 (eng.) WELL KNOWN Socket Numbers
RFC 349 (eng.) Proposed Standard Socket Numbers (canceled RFC 433)
RFC 433 (eng.) Socket Number List (canceled RFC 503)
RFC 503 (eng.) Socket Number List (canceled RFC 739)
RFC 739 (eng.) Assigned Numbers (The first list of assigned numbers was replaced by RFCs, the last of which RFC 1700)
RFC 768 (eng.) User Datagram Protocol
RFC 793 (eng.) Transmission Control Protocol
RFC 1700 (eng.) Assigned Numbers (The last list of assigned numbers is canceled RFC 3232)
RFC 3232 (eng.) Assigned Numbers: RFC 1700 IS Replaced by An On-Line Database
RFC 4340 (eng.) Datagram Congestion Control Protocol (DCCP) - Proposed Standard

Wikimedia Foundation. 2010.

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The need for access to a remote printer may occur from users of a wide variety of applications: a text editor, a graphical editor, a database management system (DBMS). Obviously, duplication in each of the applications common for all of them functions on the organization of remote printing is redundant.

A approach is more effective in which these functions are excluded from applications and are made in the form of a pair of specialized client software modules and a print server (Fig.), The functions of which were previously executed according to applications A and B. Now this pair client server can be used by any application. performed on computer A.

Summarizing this approach in relation to other types of resources shared, let the following definitions:

Client - This is a module designed to form and transmit message requests to a remote computer resources from different applications with subsequent reception of results from the network and transferring them to the relevant applications.

Server - This is a module that is constantly waiting for coming from the customer requests network, and accepting the request, trying to serve it, as a rule, with the participation of the local OS; One server can serve the requests of several customers at once (alternately or at the same time).

Couple clientThe server that provides access to a specific type of computer resource through the network forms network service.

Each service is associated with a specific type of network resources. So, in fig. Client and server modules that implement remote access to the printer form a network printing service.

File service Allows you to access files stored on the disk of other computers. Server file service component is called file server.

To search and view information on the Internet, a web service is used, consisting of a web server and a client program called a web browser (Web Browser). The shared resource in this case is the website in a particularly organized set of files containing information connected in meaning and stored on the external web server drive.

On the web service scheme shown in Fig. Two computers are not connected directly as it was in all previous examples, but through many intermediate computers and other network devices that are part of the Internet. In order to reflect this fact graphically, we placed between two computers the so-called communication cloud that allows us to abstract from all the details of the messaging environment. Messaging between client and server parts of the web service is performed according to the standard HTTP protocol and does not depend on whether these messages are "from hand to hand" messages (from the interface of one computer to the other interface) or through a large number of intermediaries - transit communication devices . At the same time, the complication of the messaging environment leads to new additional tasks, the solution of which was not designed previously the simplest network interface card driver. Instead, more developed software vehicles should be installed on interacting computers.

Network operating system

The computer's operating system is often defined as a interconnected system of system programs that provides effective computer resource management (memory, processor, external devices, files, etc.), and also provides the user with a user-friendly interface for working with computer equipment and application development.

Speaking about the network OS, we obviously have to expand the boundaries of managed resources beyond the same computer.

Network operating system They call the computer's operating system, which in addition to managing local resources provides users with users and applications the ability to effectively and convenient access to information and hardware resources of other network computers.

Today, almost all operating systems are network.

From the examples discussed in previous sections, we see that remote access to network resources is provided:

· Network services;

· Tools for transport messages over a network (in the simplest case - network interface cards and their drivers).

Consequently, it is these functional modules that must be added to the OS so that it can be called network (Fig.).

Among the network services, you can select those that are not focused on a simple user, such as the file service or print service, and on the administrator. Such services are aimed at organizing the network. For example, a centralized reference service, or directory service, is designed to maintain a database on network users, about all its software and hardware components *. As other examples, you can call the network monitoring service that allows you to capture and analyze network traffic, the security service, in the functions of which can be included, in particular, performing a logical entry procedure with a password check, backup service and archiving.

From how much a rich set of network services and services offers an operating system to end users, applications and network administrators depends on its position in the total number of network OS.

In addition to network services, the Network OS should include software communication (transport) means providing together with hardware communication messages that communicate client and server parts of network services. The task of communication between the network computers solve drivers and protocol modules. They perform features such as the formation of messages, partitioning the message to parts (packets, frames), converting computer names to numeric addresses, duplicating messages in case of their loss, determining the route in a complex network, etc.

And network services, and vehicles may be integral (embedded) OS components or exist as separate software products. For example, a network file is usually embedded in OS, but the web browser is most often purchased separately. A typical network OS has a wide range of drivers and protocol modules, however, the user will usually have the opportunity to supplement this standard set by the programs necessary for it. The decision on the method of implementing customers and network service servers, as well as drivers and protocol modules is made by developers, taking into account the most different considerations: technical, commercial and law. For example, precisely on the basis of the US antitrust law, Microsoft was forbidden to include its Internet Explorer browser in the OS of this company.

The network service can be represented in OS or both (client and server) parts, or only one of them.

In the first case, the operating system, called peer-to-peer, not only allows you to access the resources of other computers, but also provides its own resources at the disposal of users of other computers. For example, if clients and file service servers are installed on all network computers, then all network users can share each other files. Computers that combine client and server functions are called peer-to-peer nodes.

The operating system, which mainly contains client parts of network services, is called client. Client OS are installed on computers that appeal to the resources of other network computers. For computers, also called client, ordinary users work. Usually, client computers belong to the class of relatively simple devices.

Another type of operating systems includes server OS - it is focused on processing requests from the network to the resources of the computer and includes mainly server parts of network services. A computer with a server OS installed on it, which is solely servicing other computers, is called a dedicated network server. For a dedicated server, as a rule, ordinary users do not work.

Network applications

The computer connected to the network can perform the following types of applications:

· The local application is entirely performed on this computer and uses only local resources (Fig. Oh). No network tools are required for such an application, it can be performed on a self-operating computer.

· The centralized network application is entirely performed on this computer. But addresses in the process of its execution to the resources of other network computers. B Example in Figure B The application that runs on the client computer processes the data from the file stored on the file server, and then prints the results on the printer connected to the print server. Obviously, the work of this type of application is impossible without the participation of network services and means of transporting messages.

· Distributed (network) application consists of several interacting parts, each of which performs some particular completed work to solve the application problem, and each part can be performed and, as a rule, is performed on a separate network computer (Fig. B). Parts of a distributed application interact with each other using network services and vehicles OS. Distributed application in the general case has access to all computer network resources.

An obvious advantage of distributed applications is the ability to parallelize computing, as well as computer specialization. Thus, in the application, for example, for the analysis of climatic changes, it is possible to distinguish three sufficiently independent parts (see Fig. 2.6, B), allowing parallelization. The first part of the application, which is performed on a relatively low-profile personal computer, could maintain a specialized graphical user interface, the second is to engage in statistical data processing on high-performance mainframe, and the third - generate reports on the server with the installed standard DBMS. In general, each part of the distributed application can be represented by several copies running on different computers. For example, in this example, part 1, responsible for supporting the specialized user interface, could be launched on several personal computers, which would work with this application to several users simultaneously.

However, to achieve all the advantages that distributed applications, developers of these applications have to solve many problems, for example: how many parts should be divided by an application which functions to assign to each part, how to organize the interaction of these parts so that in case of failures and failures, the remaining parts Correctly completed work, etc., and so on.

Note that all network services, including file service, print service, email service, remote access service, internet telephony, etc., by definition refer to the class of distributed applications. Indeed, any network service includes client and server parts that can and usually run on different computers.

In fig. 2.7, illustrating the distributed nature of the web service, we see different types of client devices - personal computers, laptops and mobile phones - with web browsers installed on them that interact over the network with a web server. Thus, with the same website, a lot of hundreds and thousands of network users can simultaneously work at the same time.

Numerous examples of distributed applications can be found in such a area as processing these scientific experiments. This is not surprising, since many experiments generate such large amounts of data generated in real time, which simply cannot be processed on one, even very powerful, supercomputer. In addition, experimental data processing algorithms are often easily parallelized, which is also important for the successful use of interrelated computers in order to solve any common task. One of the last and very well-known examples of a distributed scientific application is the data processing software of a large hadron collider (Large Hadron Collider, LHC), launched on September 10, 2008 in CERN - this application works more than 30 thousand computers united in the network.

CCS.

The CCS Internet provider provides communication services, ranging from access to a network and telephony and ending with the placement of equipment in data centers and system integration. The company's web channel is united with powerful lines of communication of the global and Russian Internet segments.

Tariffs on the Internet CCS

The provider is developing an organization's scheme individually for each client, selecting technical options and creating complex and multi-level connections. Connecting to the network can be implemented with a maximum speed of 10 Gbps per second.

Features

CCS perfectly combines services and technologies, achieving maximum efficiency and organization. Working with one provider involved in the entire complex of telecommunication services is easier and more convenient than with several different. The quality of services is achieved by an individual approach and selection of optimal solutions for customer development. Technical support for consultation and solving tasks is working daily and around the clock.

The set of server and client parts of the OS providing access to a specific type of computer resource through the network is called a network service. In the example above, the client and server part of the OS, which jointly provide access via the network to the computer file system form the file service.

It is said that the network service provides network users some set of services. These services are sometimes called the network service (from the English-speaking term "Service"). It should be noted that this term in the technical literature is translated as "service", and both "service" and as a "service". Although the specified terms are sometimes used as synonyms, it should be borne in mind that in some cases the difference in the values \u200b\u200bof these terms is fundamental. Further in the text under the "service" we will understand the network component that implements some set of services, and under the "service" - a description of the set of services provided by this service. Thus, the service is the interface between the consumer services and the service provider (service).

Each service is associated with a specific type of network resources and / or a certain way to access these resources. For example, the print service provides network users access to shared network printers and provides a print service, and the postal service provides access to the network information resource - emails. The method of access to resources is different, for example, a remote access service - it provides computer network users access to all its resources through switched telephone channels. To obtain remote access to a specific resource, such as a printer, the remote access service interacts with the print service. The most important for users of the network OS is the file service and the print service.

Among the network services, you can select those that are not focused on a simple user, but on the administrator. Such services are used to organize the network. For example, the Bindery service of the Novell NetWare 3.x operating system allows the administrator to database on network users of the computer on which this OS is running. More progressive is an approach with the creation of a centralized reference service, or, differently, the directory service, which is intended for maintaining a database not only about all network users, but also about all its software and hardware components. NOVELL and Streettalk NDS are often given as NDS of the NOVELL and StreetTalk company of Banyan. Other examples of network services providing the service administrator are a network monitoring service that allows you to capture and analyze network traffic, the security service, in the function of which can be included, in particular, the execution of a logical entry procedure with a password check, backup and archiving service. From how much a rich service kit offers an operating system to end users, applications and network administrators depends on its position in the total number of network OS.

Network services are by their nature are client-server systems. Since when implementing any network service, the source of queries (client) and the executive of requests (server), then, and any network service contains two asymmetric parts in its composition - client and server (Fig. 2.2). The network service can be represented in the operating system or both (client and server) parts, or only one of them.

Fig. 2.2.

It is usually said that the server provides its resources to the client, and the client uses them. It should be noted that when providing a network service of some service, resources are used not only by the server, but also the client. The client can spend a significant part of its resources (disk space, processor time, etc.) to maintain the operation of the network service. For example, when implementing the postal service on a client disk, a local copy of the database containing its extensive correspondence can be stored. In this case, the client performs a great job when generating messages in various formats, including complex multimedia, supports the maintenance of the address book and performs many more different auxiliary work. The principled difference between the client and the server is that the client is always the initiator of the work of the work of the network service, and the server is always in passive queries' expectation mode. For example, the mail server delivers mail to the user's computer only when requesting a request from the mail client.

Usually, the interaction between client and server parts is standardized, so that one type of server can be designed to work with clients of different types, implemented in various ways and, maybe different manufacturers. The only condition for this - clients and the server must support the overall standard interaction protocol.

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