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شركت سيسكو در سال‌هاي 1996 تا 1999 تعداد يك ميليون عدد از اين تجهيزات را فروخت، در حالي كه در سال 2000 به تنهايي يك ميليون عدد ديگر از اين تجهيزات توسط اين شركت به فروش رسيد. اين آمار خود بيان‌گر سرعت رشد اين فناوري است. تجارت بزرگ در زمينه VoIP امروزه VoIP و انتقال صوت بر پايه اين فناوري به صورت يك تجارت بزرگ در آمده است كه هم‌چنان روند رو به رشد بالايي دارد. مزيت اصلي اين نوع مكالمات براي كاربران، هزينه پايين آن است كه موجب ترجيه آن به شبكه هاي مخابراتي سنتي مي‌شود.

 فروش گوشي هاي تلفني جديد: براي پشتيباني بهتر فناوري VoIP گوشي‌هاي تلفني خاصي ساخته شده‌اند كه خود به طور مستقيم به شبكه مبتني بر پايه IP (براي مثال اينترنت) متصل مي‌شوند و مي‌توانند اطلاعات را در قالب بسته‌هاي داده بر روي اين شبكه منتقل نمايند. تا سال 2001 در آمد ناشي از فروش اين گونه گوشي‌ها براي سازنده‌هاي آن‌ها حدود يك ميليارد دلار بود ..

ارايه خدمات در قالب مراكز تلفني نسل بعد: با وجود عدم وابستگي تكنولوژي VoIP به مراكز مخابراتي،‌ به منظور ايجاد سهولت در برقراري ارتباط (براي مثال توزيع شماره تلفن به كاربران) و ارايه سرويس‌هاي مختلف مراكز تلفني VoIP بر روي شبكه اينترنت شكل گرفته‌اند كه پيش‌بيني مي‌شود اين مراكز در آينده داراي درآمد بالايي باشند .
 

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شبكه‌هاي تلفني آينده

مراكز VoIP نيز همانند مراكز مخابراتي سنتي مي‌توانند شماره تلفني را به صورت اختصاصي به يك كاربر اختصاص دهند. اين شماره‌هاي تلفني از طريق مراكز اينترنتيVoIP در اختيار كاربران قرار مي گيرد، مانند يك آدرس پست الكترونيكي به همراه يك كلمه عبور محافظت مي‌شود.

 از طريق اين شماره كاربران مي توانند به مركز اينترنتي مزبور متصل شوند و IP دستگاه VoIP خود را به اين مركز اعلام كنند. در نتيجه كاربران ديگر توسط شماره تلفن خود به مركز VoIP متصل مي‌شوند و شماره‌اي كه قصد تماس با آن دارند را در اختيار مركز قرار داده و IP مقصد را دريافت مي‌كنند و از طريق پروتكلIP يك تماس تلفني را آغاز مي‌كنند.

 از چنين شبكه‌هايي با عنوان شبكه‌هاي مخابراتي آينده ياد مي‌شود و پيش‌بيني مي‌شود كه به سرعت جاي‌گزين شبكه‌هاي مخابراتي كنوني شوند. دلايل اصلي اين جاي‌گزيني برتري‌هايي است كه شبكه‌هاي مخابراتي آينده به شبكه‌هاي مخابراتي كنوني دارند و در زير به برخي از آن‌ها شاره مي‌كنيم:

 - هزينه‌ي بسيار پايين نگه‌داري شبكه‌هاي مخابراتي آينده نسبت به شبكه‌هاي مخابراتي كنوني و به دنبال آن،‌ قيمت پايين خريد يك شماره (حتا مجاني) و مكالمه‌ي تلفني.

-پشتيباني كليه امكانات مخابراتي كنوني و حتي ارايه خدمات جديد، با هزينه‌ي بسيار پايين و سهولت اجرايي بالا.

-جابه‌جايي آسان شماره‌هاي تلفني به اين معنا كه يك شماره تلفني مانند يك آدرس پست الكترونيكي از هر نقطه‌اي از دنيا قابل دسترسي خواهد بود و مي‌توان از طريق آن تماس گرفت و يا با آن ارتباط بر قرار كرد.

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قابليت برنامه‌نويسي بر روي گوشي‌هاي تلفني همانند يك گوشي موبايل و يا حتا پيشرفته‌تر از آن. در سيستم‌هاي مخابراتيVoIP سرعت برقراري ارتباط به شدت وابسته به قدرت سيستم‌هاي نهايي در برقراري ارتباط است در حالي كه در سيستم‌هاي مخابراتي كنوني اين زمان بسيار طولاني است.

اما بر روي هم رفته سرعت بر قراري ارتباط VoIP كه به وسيله سوييچ بسته‌هاي داده كار مي‌كنند به مراتب سريع‌تر از برقراري ارتباط در شبكه‌هاي سوييچ كننده مدار (شبكه هاي مخابراتي كنوني) است.

در سيستم‌هاي مخابراتي آينده (VoIP) ارايه كنندگان خدمات مخابراتي در عمل نقش واضح و تعريف شده‌اي ندارند؛ زيرا اركان اصلي برقراري ارتباط دو طرف مكالمه كننده هستند. پيش‌بيني مي‌شود كه مراكز مخابراتي آينده از طريق ارايه راهكارهاي متنوع به منظور بهبود برقراري ارتباط امرار معاش كنند. حال اين خدمات ممكن است بين دو مركز مخابراتي، به طور كامل متفاوت باشد.

دروازه‌‌هايVoIP Gateways) VoIP)

دروازه VoIP در واقع يك واسط بين تلفن‌هاي معمولي و شبكه‌هايIP هستند. كار دروازه‌هايVoIP را تا حدي مي‌توان با Modemها مقايسه كرد، با اين تفاوت كه اين دستگاه‌ها به صورت خودكار با دريافت شماره تلفن، نام كاربري و كلمه عبور مي‌توانند به يكISP متصل شوند.

افزون بر اين دروازه‌هاي VoIP به منظور ارسال بسته‌هايVoIP بهينه شده‌اند و قادر هستند تا از طريق برقراري ارتباط با مركز مخابراتيVoIP كارهاي برقراري تماس تلفني و ثبت شماره تلفن بر روي شبكه اينترنت را نيز انجام دهند. اين تجهيزات از طريق پروتكل لايه Application خاص مانند SIP با مركز مخابراتي ارتباط بر قرار مي‌كنند. درباره اين پروتكل‌ها در ادامه همين مقاله مطالبي را بيان خواهيم كرد.

 بسته‌هاي VoIP

براي برقراري يك ارتباط VoIP در سخت‌افزارهاي كاربري كار نمونه‌برداري از صدا صورت مي‌گيرد. به طور معمولصدايي به طول تقريبي 10 تا 20 ميلي ثانيه در بسته (Packet) اطلاعاتي جهت ارسال قرار مي‌گيرد. البته انواع Codec (رمز گذاري و رمزگشايي) تعريف شده‌اند كه هركدام استاندارد خاص خود را به منظور نمونه‌برداري و ارسال صدا تعريف مي‌كنند.

 هر بسته VoIP طولي كم‌تر از 100 بايت دارد كه پروتكل لايه ارسال(Transfer Protocol) UDP را جهت مسافرت بر روي شبكه IP انتخاب مي‌كند. 20 تا 40 بايت اول بسته VoIP حاوي IP مقصد است. 8 بايتي كه به دنبال آن مي‌آيد حاوي صدايي است كه در بازه زماني 10 تا 20 ميلي ثانيه نمونه‌برداري شده است. سپس 12 بايت كه اطلاعاتي از نوع پروتكل RTP را داراست در ادامه آن مي آيد. در ادامه همين مقاله توضيحاتي را در مورد اين پروتكل بيان خواهيم كرد.

بالاخره در 33 بايت انتهايي اين بسته اطلاعاتي در مورد نحوه كدگذاري و كدگشايي اين بسته (Codec Info) قرار مي‌گيرد. وا بسته به Codec در نظر گرفته شده در انتقال صدا، بسته‌هاي VoIP مدتي را در سمت ديگر (دريافت كننده صدا) منتظر مي مانند تا كار بافر شدن آنها به حد تعيين شده برسد. با رسيدن حجم بسته‌ها در بافر سمت دريافت كننده به اندازه تعيين شده، صدا در سمت ديگر پخش خواهد شد.