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Abstract

Content

Introduction

Modern information technologies play more and more important role in all spheres of activity of the person.

With distribution of computers it is easy to predict growth in requirement of data transmission. Today in the world there is more than billion computers and more than 80 percent from them are united in various information networks from small local networks at offices to global Internet networks. The world tendency to combination of computers in a network is caused by a number of the important reasons, such as acceleration of transfer of information messages, possibility of fast exchange of information between users, receiving and transmission of messages without departing from a workplace, possibility of instant obtaining any information from every spot on the globe, and as exchange of information between computers of different firms and the producers working under the different software. Use of local networks allows to facilitate access to devices of the terminal equipment of data established in establishment. These devices – not only the computer, but also other devices which are usually used in establishments, such, as printers, graph plotters and escalating number of electronic devices of storage and processing of files and databases. The local network represents the channel and data exchange protocols for communication of workstations and computers.

 

1. Relevance creation of a network

In the city of Dushanbe and around the Sino there are various networks of Internet access. Generally they are networks wireless technologies. In the area Wi-Fi WiMAX is provided services of mobile communication 3G. But connection and tariffs of these services very expensively and besides limited traffic. Exists as the DGTS network which provides services in the Dial-Up and ADSL technologies. Speed of a Dial-Up broadcast makes to 56 Kbps which doesn't correspond to this indicator. On ADSL not probably to transfer the high speed of the necessary quality, because of outdated cable system over the earth and underground. Such low speeds and qualities of transfers doesn't satisfy to requirements of the population and it is respectively expensive after the price/quality relation. Subscribers of the area need quality information services, but existing networks don't provide them. There is a problem of providing high-quality information services owing to what creation of a new multiservice network is necessary. Inhabitants of the area, and also the public and private institutions will act as subscribers of a new network.

2. Purpose and research problems

The purpose of work is elaboration of approach to design of a network of access for providing digital services in the city with the mixed building and limited solvency of subscribers. Main objectives of research:

1 . Analysis of geography and population

2. Calculation of parameters of a traffic

3. Creation of a transport network, network of access and equipment

4 Choice. Calculation of indicators of quality

5. Definition of indicators of economic efficiency

3. Information model of object

It is necessary to develop a telecommunication network which would unite all spheres of economy and management on all area. All subscribers can be divided into 3 types. Subscribers of one type have the general functions which are carried out, and also will use similar services of a network.

Table 1. – Types of subscribers of a network.


Type

Subscribers

Сервисы сети

VoIP

Internet

FTP

 

1

Network Services Room

+

+

+

 

2

Office

+

+

+

 

3

Public institutions

+

+

+

 

All services are available to all subscribers of a network. In the main knot there will be VoIP, Internet, FTP servers and Internet connection. The structure of the service Internet includes services: videoconference, Internet connection etc.

4. Topology and communication line

The topology and communication line choice the Network is under construction on three-level hierarchies: The kernel distribution Level access Level the Kernel consists of one high-speed router included in a ring of a transport network.

The network is under construction on three-level hierarchies:

The Core consists of one high-speed router included in a ring of a transport network.

4.1. Choice Topology of a transport network (distribution network)

The ring topology is optimum for a network in connection with a large number of sites and steady work without essential falling of speed of data transmission at intensive loading of a network. At such topology each knot of a network will have the address space. The address space undertakes with a stock, counting upon further to development and knot expansions.

Network model

Figure 1. – Network model

 

4.2. Topology of a network of access

For an access network in apartment houses we choose topology a star. Considering an arrangement of subscribers topology a star well it is scaled. Subscribers settle down from each other on not long distances and at refusal at one subscriber, others don't test a neudobnost.

For an access network in the private sector the topology the tire with branches is used. As in the private sector density of subscribers is small also bike distances between them. Houses are generally located along the street that such topology in more stoutly will correspond to such arrangement will manage cheaper.

4.3. Technology of a network

For creation of this network the solution of FTTB/ETTH is used. For providing with high quality and a full traffic it is used fiber-optical communication lines. In transport level 10 GB of Ethernet are used. The technology expensive, but almost it is completely loaded. In a network of access the GEPON or Ethernet technology is used. Depending on density of building and subscriber structure of the district these technologies are used. In places with smaller density of subscribers and in long distance between buildings, it is expedient to use GEPON, and in places with big density and relatives in distance of Ethernet.

5. Structure of the network

The GEPON network consists of several elements — the switchboard on a communication center, communication lines with passive splitters in knots of a network and modems on the party of subscribers. To each modem all packages from the switchboard arrive, and during transfer temporary multiplexing of shots is used [1]. At the same time, at an overload of Ethernet of turn collect in switchboards which in principle have very limited opportunities for recognition of overloads and reaction to them. At an overload of GEPON of turn collect in knots senders which can react much more flexibly to their overflow — this technology has much more developed control facilities a traffic on the basis of criteria of quality.

Data transmission in the direct channel, 15 shots, 7 repeats', size 182 KB

Animation 1. Data transmission in the direct channel, 15 shots, 7 repeats', size 182 KB

 

Data transmission in the return channel, 18 shots, 7 repeats', size 190 KB

Animation 2. Data transmission in the return channel, 18 shots, 7 repeats', size 190 KB

GEPON supports logic of information exchange of IEEE 802.1p and IEEE 802.1q with priorities and turns. The IEEE 802.1p standard specifies a method of the indication of a priority of the shot, based on use of the new fields defined in the IEEE 802.1Q standard. To a shot of Ethernet two bytes are added. These 16 bits contain information on accessory of a shot of Ethernet to VLAN and about its priority. Speaking more precisely, three bits code about eight levels of a priority, 12 bits allow to distinguish a traffic to 4096 VLAN, and one bit is reserved for designation of shots of networks of other types (Token ring, FDDI), transferred on the Ethernet highway [3]. All GEPON switchboards are supported by the STP/RSTP protocols and mechanisms of prioritization of a traffic and the organization of virtual networks (including Port Based and 802.1Q). Efficiency of multiple-address mailings is provided with support of IGMP v.2, IGMP proxy, IGMP snooping and MVR [2].

 

5.1 MPCP Protocol

With subscriber knots the IEEE 802.3ah committee developed the protocol of management for the organization of interaction of the central knot a set of the MPCP hubs (multi-point control protocol). The protocol is based on two types of operating shots (messages): GATE and REPORT. Messages of GATE go from OLT to all ONT. They contain information on broadcasting modes, identifiers of the recipient, temporary tags, etc. In reply the ONT hubs send on OLT of the message of REPORT in which transfer information on the conditions. Messages of REPORT help OLT to distribute correctly a strip in the return stream [1].

GATEREPORT

Figure 2. – Format of the message a) GATE and b) REPORT [5].

The MPCP protocol has two operating modes: mode of initialization (autoregistration) and normal operating mode. Respectively and subscriber knots can is in two conditions. The mode of initialization is necessary in order that OLT could find and register the new ONT hubs. The LLID identifier to registered ONT is thus appointed, delay time on double run of RTT (round trip time) to this ONT is calculated, and other parameters are defined. The normal operating mode serves directly for data transmission [1].

The preamble of a standard shot of Ethernet, fig. 3a, is modified by addition of several office fields, fig. 3b:

More detailed description of fields of shots

Figure 3. – More detailed description of fields of shots [5].

The priority of a shot contains in the VLAN tag. From 16 bits, 12 carry information on VLAN, and 3 bits indicate a priority. Thus shots can be 8 priorities, from 000-111. Information on a priority is stored in a tag 802.1q.Очереди gather in ONU. It distributes them in turns considering a priority and gives to OLT information about filling of turns. The big preamble (8 bytes) which was in classical Ethernete is modified in EPON, some office fields are added. It contains the most important information – LLID which specifies to what ONU is intended a shot.

 

For evident comparison the table of comparison of Ethernet and PON is provided. Proceeding from the table we see that the PON networks cede nothing Ethernet, in some пунтах surpass.

 

Table 2. – Ethernet and PON technology comparison [4].

Ethernet

PON

Usually some intermediate knots with the active equipment between knot of the operator and subscribers

Completely passive network between knot of the operator and subscribers

Need of protection and equipment reservation on intermediate active knots

Need of carrying out calculations of the optical budget at installation of passive optical splitters

Point of differentiation of zones of responsibility – the socket with the brought cable of the house at the subscriber

Point of differentiation of zones of responsibility – the subscriber ONU device

Very labor-consuming management of a network in view of usually extensive network of active knots

Built-in mechanisms of management and monitoring. ONU management from the uniform center. The subscriber of access to ONU has no

Low cost of the decision because of absence at the user of the subscriber device

Higher cost of the decision in view of use of subscriber ONU devices

Simplicity of installation

More difficult installation

Technological restrictions, for example, distance of 100 m from active knot to the subscriber

There are no special restrictions in view of use of a fiber-optical cable

 

 

Все абоненты получают услуги в зависимости от их требования. Абоненты пользуются услугами  в разные время суток, соответственно сеть нагружается в определенные время суток, в основном в час пик.

Table 3. - Parameters of a traffic of subscribers

service the maximum speed of kbps пачечность  Communication session duration
f
 Entering loadings at an O'clock of the greatest loading (Earl) Y
room subscribers commercial subscribers state office room subscriber commercial subscribers state office
 IP телефония 35 1 180 2 5 4 0,1 0,25 0,2
Интернет 2048 10 3 30 50 40 0,025 0,042 0,033
Передача файлів 4096 10..100 1200 0,1 0,05 0,02 0,033 0,017 0,007

 

 

Conclusions

Development of a technique design of networks promotes fast acceptance the decision and to save time. In advance developed, checked techniques provide qualitative design of networks. With growth of need of subscribers we can passes from GEPON to Ethernet, with use of the same fiber-optical cables.

 

This master's work is not completed yet. Final completion: December 2013. The full text of the work and materials on the topic can be obtained from the author or his head after this date.

References

  1. Протокол MPCP/ Internet resource. – Mode of access: www/ URL: http://www.teralink.ru/?do=stech2&id=882
  2. Волокно в каждый дом: как это работает. Технология GEPON/ Internet resource. – Mode of access: www/ URL: http://www.ixbt.com/comm/zyxel-gepon.shtml
  3. IEEE 802.1p/ Internet resource. – Mode of access: www/ URL: http://ru.wikipedia.org/wiki/IEEE_802.1p
  4. Ставка на GEPON/ Internet resource. – Mode of access: www/ URL: http://imaqliq.com/information/press/stavka_na_gepon/
  5. Пассивные оптические сети (PON/EPON/GEPON)/ Internet resource. – Mode of access: www/ URL: http://book.itep.ru/4/41/pon.htm