Codec G.726: Recommendation G.726 is based on algorithm of coding ADPCM - adaptive differential ИКМ. This algorithm gives almost same quality of reproduction of speech, as well as ИКМ, however for an information transfer at its use the strip only 16-32 kbit/c is required. The codec is intended for use in systems of videoconferences, in IP-telephony appendices this codec practically is not used. The estimation on MOS makes 4.3.

Codec G.728: uses original technology with small delay LD-CELP (low delay code excited linear prediction) and guarantees estimations MOS similar G.726 at speed of transfer of 16 Kbit/c. It is intended for use, basically, in systems of videoconferences. In IP-telephony devices the given codec is applied seldom enough.

Codec G.729: technology CS-ACELP (Conjugate Structure v Algebraic Code Excited Linear Prediction) Is used. Contains VAD and the generator of comfortable noise. Speed of the coded speech signal makes 8 kbit/c. In devices VoIP, VoFR the given codec occupies in the lead position, providing

Technology of network transport

The transport network (highway) is one of the most expensive parts of any network. Through it there passes a considerable part of the traffic of a network, its properties are designated practically on all services of a corporate network which end users use. At a choice of technology of construction of the main network it is necessary to lean against the basic requirement to our network - мультисервисность. The technology is defined by used reports of the bottom level, such as Ethernet, ATM, etc. and essentially influences types of the communication equipment used in a network

For today there is a considerable quantity of network transport reports which are used for construction of the main networks. Among them it is possible to allocate ATM, FDDІ and Ethernet. The given reports are transport and focused on use in the big main networks. Each of reports has the own topology, different speeds of data transmission, excellent ways of interaction with QoS have the guaranteed delivery of packages and приоритизацию the traffic.

The active network equipment for the organisation of a network on the basis of reports ATM, FDDІ is expensive enough pleasure and will not be defensible at introduction on object of designing.

It is necessary to pay attention to one of переспективних of standards today, namely Gіgabіt Ethernet family of reports ІEEE 802.3. Being based on above written, we will stop a choice on technology GE. For reliability and fault tolerance increase the main network will have topology of type a ring (logic), but as it is known the family of reports Ethernet does not support a sheaf of such kind. The ring topology is unacceptable and causes collisions at network work. For the decision of this problem it is necessary to take advantage of report STP.

Technology of network distribution/access

In all areas at access level technology Fast Ethernet will work. It is caused by that the given technology is universal for construction of IP-networks, and at transport level technology GE, from семейтсва Ethernet is chosen.

ast Ethernet - the specification ІEЕЕ 802.3u defines the standard of the report of channel level for those networks which use both copper, and a fiber-optical cable with a speed 100Mb/with. The new specification is the successor of standard Ethernet ІEЕЕ 802.3, using the same format of a shot, the access mechanism by Wednesday of CSMA/CD and topology a star. Evolution has mentioned several elements of a configuration of means of physical level which has allowed to increase throughput.

The basic advantages of technology Fast Ethernet are: increase in throughput of segments of a network to 100 Mb/c; preservation of a method of casual access Ethernet; preservation of star-shaped topology of networks and support of traditional environments of data transmission - twisted pair and a fibre-optical cable.

Network function chart

In drawing 4.1 resulted function chart of a segment of a network. According to the scheme - multiplexer DSLAM is the boundary device between «last mile» and a data transmission network.

Joins DSLAM a data transmission network through the switchboard and an access router on technology Fast Ethernet (100 Вase-TХ). Further the access router on technology Fast Ethernet is included in level of distribution, which in turn through Gigabit Ethernet (10 Gbit/c) in a router of a kernel which has access to the network Internet. At level of a transport network technology Gigabit Ethernet (40 Gbit/c) under the standard 802.3ba works.

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