Voice-Enabling the Frame Relay Network
Before explaining the importance of voice switching, it is necessary to describe the methods implemented to enable the Frame Relay network to carry voice as well as data. In particular, some of the common voice-enabling techniques incorporated into voice Frame Relay access devices (VFRADs) are described below.
Fragmentation - Data packets are divided into small frames, allowing higher priority voice packets to receive the right-of-way without waiting for the end of long data transmissions. This minimizes delay of voice communications and has no negative effect on data traffic, as voice transmissions are relatively short and require little bandwidth.
Prioritization of voice traffic - When voice and data frames leave the VFRAD, prioritization ensures that voice traffic is sent first.
Voice compression - Voice compression maximizes bandwidth, allowing Frame Relay links to most effectively carry a combination of voice and data sessions without compromising voice quality. Since Frame Relay access is usually 56/64 kbps, low bit- rate voice compression standards such as ITU G: 723,1 an~ ITU G. 729 A permit the greatest number of simultaneous multiple calls while maintaining high quality voice.
Silence suppression - The VFRAD can detect silence and refrains from sending silence packets. In a typical telephone conversation, one person talks while the other person listens. The silence on the listener's end is not sent over the network, saving 50% of the full duplex .link. In addition, voice packets are not sent during interword pauses or natural pauses in the conversation, reducing the required bandwidth by another 10%. Silence suppression frees this 60% of bandwidth on the full duplex link for other voice or data transmissions.
Jitter buffer - Variable delay in the arrival times between packets (also called jitter) is even more troublesome than overall delay for voice transmissions. Jitter results in unnatural-sounding voice instead of a smooth voice stream. A jitter buffer employed
Supports flexible numbering plan. Within the same network, extension numbers can contain a varying number of digits. This is enabled by the short dialing (SD) feature of
the MAXcess VFRAD, which permits a timeout after each digit dialed. Notice in the illustration below that extension numbers at the Singapore office are made up of five digits, whereas they contain four digits at all other MAXcess sites.
Transparent lntrgration of Voice and Data
% represents all other numbers; and
SD represents short dialing (a shortcut to receiving an access code). Dialing "3" at the New Jersey site routes the call to the New York MAXcess device. From there, calls starting with "3" are routed to the Singapore PSTN. This feature enables remote sites to place local calls in each location in the network. Dialing "1" exits to the local PSTN in New Jersey. The routing tables at the MAXcess VFRADs at the destination sites (Singapore and New Jersey) indicate to truncate the access code ("3" and "1," respectively, in this example) before forwarding the number string to the PSTN.
Note that all other outgoing calls are sent via DLCI 16, where they are switched according to the routing table at the New York office.
To call Bob in Los Angeles, Ted (New Jersey) would dia14010. Since "40" does not appear in the routing table of the New Jersey node, Ted's MAXcess unit sends the call to New York via DLCI 16, according to the "%" default entry. The routing table at the New York MAXcess unit sends the call (and all other calls beginning with "40") to the Los Angeles office via DLCI 21.
When Bob (Los Angeles) places a call, any dialed number that does not begin with "40" is routed to Node 30 (New York), which further routes it to its next hop in the network.
Note that extension nlU11bers are not listed in the routing tables. Rather, each MAXcess sends calls to the next hop in the network. It is routed internally when it reaches the final site.
RAD's voice switching system is completely scalable. A network can be divided into the combination of Zones and Nodes that facilitates the simplest voice switching and routing tab les.
Minimal Number of Links between Sites
wie wil dit plz voor mij in het nederlands vertalen, gebruik aub geen vertaler want dat kan je zien, en dat kan ik zelf ook

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help me aub, ik kan totaal geen engels en moet dit maandag voor een cijfer inleveren.
heel hartelijk dank