{"id":3121,"date":"2026-04-20T02:30:32","date_gmt":"2026-04-20T02:30:32","guid":{"rendered":"https:\/\/multahost.com\/blog\/?p=3121"},"modified":"2026-04-20T02:52:35","modified_gmt":"2026-04-20T02:52:35","slug":"vos3000-sip-session-timer-guide","status":"publish","type":"post","link":"https:\/\/multahost.com\/blog\/vos3000-sip-session-timer-guide\/","title":{"rendered":"VOS3000 SIP Session Timer: Powerful RFC 4028 Setup Guide"},"content":{"rendered":"\n<h1 class=\"wp-block-heading\" id=\"vos-3000-sip-session-timer-powerful-rfc-4028-setup-guide\">VOS3000 SIP Session Timer: Powerful RFC 4028 Setup Guide<\/h1>\n\n\n\n<p>\ud83d\udcde Are mysterious <strong>ghost calls<\/strong> and <strong>ultra-long bills<\/strong> draining your VoIP revenue? The <strong>VOS3000 SIP session timer<\/strong> is your first line of defense. Based on <strong>RFC 4028<\/strong>, this critical SIP protocol feature detects whether calls are still alive \u2014 and automatically hangs up dead sessions before they inflate your billing. \u23f1\ufe0f<\/p>\n\n\n\n<p>\ud83d\udd27 In abnormal network conditions, SIP endpoints can lose connectivity without sending a proper BYE message. Without session timers, these <strong>zombie calls<\/strong> linger indefinitely, generating charges for conversations that ended long ago. VOS3000 solves this with four powerful parameters that control how session timers operate across your entire softswitch.<\/p>\n\n\n\n<p>\ud83c\udfaf This guide walks you through every VOS3000 SIP session timer parameter \u2014 from <strong>SS_SIP_SESSION_TTL<\/strong> to <strong>SS_SIP_NO_TIMER_REINVITE_INTERVAL<\/strong> \u2014 with real default values, configuration steps, and best practices to keep your VoIP network clean and profitable.<\/p>\n\n\n\n<div class=\"wp-block-rank-math-toc-block\" id=\"rank-math-toc\"><h2>Table of Contents<\/h2><nav><ul><li><a href=\"#vos-3000-sip-session-timer-powerful-rfc-4028-setup-guide\">VOS3000 SIP Session Timer: Powerful RFC 4028 Setup Guide<\/a><ul><li><a href=\"#\ud83d\udd10-what-is-vos-3000-sip-session-timer\">\ud83d\udd10 What Is VOS3000 SIP Session Timer?<\/a><ul><li><a href=\"#\ud83d\udccb-rfc-4028-core-concepts-for-vos-3000\">\ud83d\udccb RFC 4028 Core Concepts for VOS3000<\/a><\/li><\/ul><\/li><li><a href=\"#\u2699\ufe0f-vos-3000-sip-session-timer-parameters-deep-dive\">\u2699\ufe0f VOS3000 SIP Session Timer Parameters Deep Dive<\/a><ul><li><a href=\"#\ud83d\udd11-ss-sip-session-ttl-detecting-sip-connected-status-interval\">\ud83d\udd11 SS_SIP_SESSION_TTL \u2014 Detecting SIP Connected Status Interval<\/a><\/li><li><a href=\"#\ud83d\udd04-ss-sip-session-update-segment-reinvite-interval-divider\">\ud83d\udd04 SS_SIP_SESSION_UPDATE_SEGMENT \u2014 Reinvite Interval Divider<\/a><\/li><li><a href=\"#\u23f0-ss-sip-session-timeout-early-hangup-early-hangup-timer\">\u23f0 SS_SIP_SESSION_TIMEOUT_EARLY_HANGUP \u2014 Early Hangup Timer<\/a><\/li><li><a href=\"#\ud83d\udda5\ufe0f-ss-sip-no-timer-reinvite-interval-non-timer-sip-caller-limit\">\ud83d\udda5\ufe0f SS_SIP_NO_TIMER_REINVITE_INTERVAL \u2014 Non-Timer SIP Caller Limit<\/a><\/li><\/ul><\/li><li><a href=\"#\ud83d\udccb-how-vos-3000-sip-session-timer-works-complete-flow\">\ud83d\udccb How VOS3000 SIP Session Timer Works \u2014 Complete Flow<\/a><ul><li><a href=\"#\ud83c\udfaf-scenario-a-caller-supports-session-timer\">\ud83c\udfaf Scenario A: Caller SUPPORTS Session Timer<\/a><\/li><li><a href=\"#\ud83c\udfaf-scenario-b-caller-does-not-support-session-timer\">\ud83c\udfaf Scenario B: Caller Does NOT Support Session Timer<\/a><\/li><\/ul><\/li><li><a href=\"#\ud83d\udd27-step-by-step-vos-3000-sip-session-timer-configuration\">\ud83d\udd27 Step-by-Step VOS3000 SIP Session Timer Configuration<\/a><ul><li><a href=\"#step-1-navigate-to-sip-parameters-\ud83d\udccb\">Step 1: Navigate to SIP Parameters \ud83d\udccb<\/a><\/li><li><a href=\"#step-2-configure-ss-sip-session-ttl-\u23f1\ufe0f\">Step 2: Configure SS_SIP_SESSION_TTL \u23f1\ufe0f<\/a><\/li><li><a href=\"#step-3-set-ss-sip-session-update-segment-\ud83d\udd04\">Step 3: Set SS_SIP_SESSION_UPDATE_SEGMENT \ud83d\udd04<\/a><\/li><li><a href=\"#step-4-configure-early-hangup-\u23f0\">Step 4: Configure Early Hangup \u23f0<\/a><\/li><li><a href=\"#step-5-adjust-non-timer-caller-limit-\ud83d\udcf1\">Step 5: Adjust Non-Timer Caller Limit \ud83d\udcf1<\/a><\/li><\/ul><\/li><li><a href=\"#\ud83d\udcca-complete-vos-3000-sip-session-timer-parameter-reference\">\ud83d\udcca Complete VOS3000 SIP Session Timer Parameter Reference<\/a><\/li><li><a href=\"#\ud83d\udee1\ufe0f-common-vos-3000-sip-session-timer-problems-and-solutions\">\ud83d\udee1\ufe0f Common VOS3000 SIP Session Timer Problems and Solutions<\/a><ul><li><a href=\"#\u274c-problem-1-calls-dropping-every-5-minutes\">\u274c Problem 1: Calls Dropping Every 5 Minutes<\/a><\/li><li><a href=\"#\u274c-problem-2-ultra-long-bills-from-zombie-calls\">\u274c Problem 2: Ultra-Long Bills from Zombie Calls<\/a><\/li><li><a href=\"#\u274c-problem-3-excessive-signaling-overhead\">\u274c Problem 3: Excessive Signaling Overhead<\/a><\/li><\/ul><\/li><li><a href=\"#\ud83d\udca1-vos-3000-sip-session-timer-best-practices\">\ud83d\udca1 VOS3000 SIP Session Timer Best Practices<\/a><\/li><li><a href=\"#\ud83d\udd04-vos-3000-sip-session-timer-and-sip-call-flow-interaction\">\ud83d\udd04 VOS3000 SIP Session Timer and SIP Call Flow Interaction<\/a><\/li><li><a href=\"#\ud83d\udd10-verifying-vos-3000-sip-session-timer-operation\">\ud83d\udd10 Verifying VOS3000 SIP Session Timer Operation<\/a><ul><li><a href=\"#using-sip-debug-to-confirm-timer-negotiation-\ud83d\udd0d\">Using SIP Debug to Confirm Timer Negotiation \ud83d\udd0d<\/a><\/li><\/ul><\/li><li><a href=\"#\u2753-frequently-asked-questions\">\u2753 Frequently Asked Questions<\/a><ul><li><a href=\"#\u2753-what-is-the-default-vos-3000-sip-session-timer-value\">\u2753 What is the default VOS3000 SIP session timer value?<\/a><\/li><li><a href=\"#\u2753-how-does-vos-3000-handle-sip-callers-that-do-not-support-session-timers\">\u2753 How does VOS3000 handle SIP callers that do not support session timers?<\/a><\/li><li><a href=\"#\u2753-can-i-set-ss-sip-session-update-segment-to-1\">\u2753 Can I set SS_SIP_SESSION_UPDATE_SEGMENT to 1?<\/a><\/li><li><a href=\"#\u2753-what-happens-when-vos-3000-sip-session-timer-detects-a-dead-call\">\u2753 What happens when VOS3000 SIP session timer detects a dead call?<\/a><\/li><li><a href=\"#\u2753-is-the-vos-3000-sip-session-timer-compliant-with-rfc-4028\">\u2753 Is the VOS3000 SIP session timer compliant with RFC 4028?<\/a><\/li><li><a href=\"#\u2753-should-i-enable-ss-sip-session-timeout-early-hangup\">\u2753 Should I enable SS_SIP_SESSION_TIMEOUT_EARLY_HANGUP?<\/a><\/li><li><a href=\"#\u2753-how-does-vos-3000-sip-session-timer-prevent-ultra-long-bills\">\u2753 How does VOS3000 SIP session timer prevent ultra-long bills?<\/a><\/li><\/ul><\/li><li><a href=\"#\ud83d\udcde-need-expert-help-with-vos-3000-sip-session-timer\">\ud83d\udcde Need Expert Help with VOS3000 SIP Session Timer?<\/a><\/li><li><a href=\"#\ud83d\udcda-related-resources\">\ud83d\udcda Related Resources<\/a><\/li><li><a href=\"#\ud83d\udcde-need-call-center-setup-support\">\ud83d\udcde Need Professional VOS3000 Setup Support?<\/a><\/li><\/ul><\/li><\/ul><\/nav><\/div>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\ud83d\udd10-what-is-vos-3000-sip-session-timer\">\ud83d\udd10 What Is VOS3000 SIP Session Timer?<\/h2>\n\n\n\n<p>\u23f0 The <strong>VOS3000 SIP session timer<\/strong> is a built-in mechanism that periodically verifies whether a SIP call is still active. It follows the <strong>RFC 4028 SIP Session Timers<\/strong> standard, which defines how SIP User Agents can request, negotiate, and maintain session timers during a call.<\/p>\n\n\n\n<p>\ud83d\udca1 <strong>Why it matters:<\/strong> In VoIP networks, network failures, NAT timeouts, and endpoint crashes can leave calls in a &#8220;connected&#8221; state even after both parties have stopped communicating. The VOS3000 SIP session timer prevents these orphaned calls by:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\ud83d\udd04 Periodically sending re-INVITE or UPDATE messages to confirm the call is still alive<\/li>\n\n\n\n<li>\u274c Automatically hanging up calls when no confirmation is received<\/li>\n\n\n\n<li>\ud83d\udee1\ufe0f Preventing ultra-long bills caused by zombie sessions<\/li>\n\n\n\n<li>\ud83d\udcca Detecting abnormal network conditions in real time<\/li>\n<\/ul>\n\n\n\n<p>\ud83d\udccd <strong>Location in VOS3000 Client:<\/strong> Navigation \u2192 Operation management \u2192 Softswitch management \u2192 Additional settings \u2192 SIP parameter<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\ud83d\udccb-rfc-4028-core-concepts-for-vos-3000\">\ud83d\udccb RFC 4028 Core Concepts for VOS3000<\/h3>\n\n\n\n<p>\ud83c\udf10 RFC 4028 introduces the <strong>Session-Expires<\/strong> header and <strong>Min-SE<\/strong> header to SIP. Here&#8217;s how they map to VOS3000:<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><th class=\"has-text-align-left\" data-align=\"left\">RFC 4028 Concept<\/th><th class=\"has-text-align-left\" data-align=\"left\">VOS3000 Parameter<\/th><th class=\"has-text-align-left\" data-align=\"left\">Function<\/th><\/tr><tr><td>Session-Expires<\/td><td>SS_SIP_SESSION_TTL<\/td><td>Total session lifetime before refresh required<\/td><\/tr><tr><td>Refresher negotiation<\/td><td>SS_SIP_SESSION_UPDATE_SEGMENT<\/td><td>Number of refresh attempts within TTL<\/td><\/tr><tr><td>Early termination<\/td><td>SS_SIP_SESSION_TIMEOUT_EARLY_HANGUP<\/td><td>Grace period before early hangup on no response<\/td><\/tr><tr><td>Non-timer fallback<\/td><td>SS_SIP_NO_TIMER_REINVITE_INTERVAL<\/td><td>Max call duration for non-session-timer UAs<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\u2699\ufe0f-vos-3000-sip-session-timer-parameters-deep-dive\">\u2699\ufe0f VOS3000 SIP Session Timer Parameters Deep Dive<\/h2>\n\n\n\n<p>\ud83d\udd27 Let&#8217;s examine each parameter in detail using the official VOS3000 2.1.9.07 manual data.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\ud83d\udd11-ss-sip-session-ttl-detecting-sip-connected-status-interval\">\ud83d\udd11 SS_SIP_SESSION_TTL \u2014 Detecting SIP Connected Status Interval<\/h3>\n\n\n\n<p>\u23f1\ufe0f <strong>SS_SIP_SESSION_TTL<\/strong> is the heart of the VOS3000 SIP session timer system. It defines the total interval (in seconds) within which VOS3000 will detect whether a SIP call is still connected.<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><th class=\"has-text-align-left\" data-align=\"left\">Attribute<\/th><th class=\"has-text-align-left\" data-align=\"left\">Value<\/th><\/tr><tr><td>\ud83d\udccc Parameter Name<\/td><td>SS_SIP_SESSION_TTL<\/td><\/tr><tr><td>\ud83d\udd22 Default Value<\/td><td>600 seconds (10 minutes)<\/td><\/tr><tr><td>\ud83d\udcd0 Unit<\/td><td>Seconds<\/td><\/tr><tr><td>\ud83d\udcdd Description<\/td><td>If SIP caller supports &#8220;session-timer&#8221;, within the time softswitch will detect connect status according to the retry times. If got no confirm message, softswitch will regard as call finish, then hang up.<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p>\ud83d\udca1 <strong>How it works:<\/strong> When a SIP caller that supports session-timer establishes a call, VOS3000 starts a countdown based on SS_SIP_SESSION_TTL. Within this period, VOS3000 divides the TTL into segments (controlled by SS_SIP_SESSION_UPDATE_SEGMENT) and sends re-INVITE or UPDATE messages at each segment boundary. If no confirmation comes back, the call is terminated.<\/p>\n\n\n\n<p>\u26a0\ufe0f <strong>Setting too low:<\/strong> A TTL of 60 seconds means frequent re-INVITEs, increasing signaling overhead. <strong>Setting too high:<\/strong> A TTL of 3600 seconds means zombie calls can persist for up to an hour. The default of 600 seconds (10 minutes) strikes a practical balance.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\ud83d\udd04-ss-sip-session-update-segment-reinvite-interval-divider\">\ud83d\udd04 SS_SIP_SESSION_UPDATE_SEGMENT \u2014 Reinvite Interval Divider<\/h3>\n\n\n\n<p>\ud83d\udcca <strong>SS_SIP_SESSION_UPDATE_SEGMENT<\/strong> controls how many times VOS3000 will attempt to refresh a session within the TTL period. It directly determines the re-INVITE or UPDATE interval.<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><th class=\"has-text-align-left\" data-align=\"left\">Attribute<\/th><th class=\"has-text-align-left\" data-align=\"left\">Value<\/th><\/tr><tr><td>\ud83d\udccc Parameter Name<\/td><td>SS_SIP_SESSION_UPDATE_SEGMENT<\/td><\/tr><tr><td>\ud83d\udd22 Default Value<\/td><td>2<\/td><\/tr><tr><td>\ud83d\udccf Range<\/td><td>2 \u2013 10<\/td><\/tr><tr><td>\ud83d\udcdd Description<\/td><td>SIP Timer reinvite (update) Interval \u2014 divides the TTL into segments<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p>\ud83c\udfaf <strong>Calculation:<\/strong> The actual re-INVITE interval = SS_SIP_SESSION_TTL \u00f7 SS_SIP_SESSION_UPDATE_SEGMENT<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><th class=\"has-text-align-left\" data-align=\"left\">TTL (seconds)<\/th><th class=\"has-text-align-left\" data-align=\"left\">Segment<\/th><th class=\"has-text-align-left\" data-align=\"left\">Re-INVITE Interval<\/th><th class=\"has-text-align-left\" data-align=\"left\">Use Case<\/th><\/tr><tr><td>600<\/td><td>2<\/td><td>300s (5 min)<\/td><td>\u2705 Default \u2014 balanced<\/td><\/tr><tr><td>600<\/td><td>4<\/td><td>150s (2.5 min)<\/td><td>\ud83d\udd27 More frequent checks<\/td><\/tr><tr><td>600<\/td><td>6<\/td><td>100s (1.7 min)<\/td><td>\ud83d\udce1 Unstable networks<\/td><\/tr><tr><td>600<\/td><td>10<\/td><td>60s (1 min)<\/td><td>\u26a0\ufe0f High overhead<\/td><\/tr><tr><td>1800<\/td><td>3<\/td><td>600s (10 min)<\/td><td>\ud83d\udcde Long calls, stable net<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p>\ud83d\udca1 <strong>Key insight:<\/strong> With the default settings (TTL=600, Segment=2), VOS3000 sends a re-INVITE every 300 seconds (5 minutes). If the far end responds with 200 OK, the session is confirmed alive. If not, the call is hung up.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\u23f0-ss-sip-session-timeout-early-hangup-early-hangup-timer\">\u23f0 SS_SIP_SESSION_TIMEOUT_EARLY_HANGUP \u2014 Early Hangup Timer<\/h3>\n\n\n\n<p>\ud83d\udd12 <strong>SS_SIP_SESSION_TIMEOUT_EARLY_HANGUP<\/strong> adds a safety net by specifying how many seconds to wait before performing an early hangup when a re-INVITE or UPDATE receives no response.<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><th class=\"has-text-align-left\" data-align=\"left\">Attribute<\/th><th class=\"has-text-align-left\" data-align=\"left\">Value<\/th><\/tr><tr><td>\ud83d\udccc Parameter Name<\/td><td>SS_SIP_SESSION_TIMEOUT_EARLY_HANGUP<\/td><\/tr><tr><td>\ud83d\udd22 Default Value<\/td><td>0 seconds (disabled)<\/td><\/tr><tr><td>\ud83d\udcd0 Unit<\/td><td>Seconds<\/td><\/tr><tr><td>\ud83d\udcdd Description<\/td><td>SIP Timer no reinvite (update) Early Hang up \u2014 extra grace period before terminating<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p>\u26a0\ufe0f <strong>When set to 0 (default):<\/strong> VOS3000 hangs up immediately when the session timer expires without confirmation. No grace period is given.<\/p>\n\n\n\n<p>\u2705 <strong>When set to a positive value:<\/strong> VOS3000 waits the specified number of seconds after the timer expires before hanging up. This gives the far end a brief window to recover from momentary network glitches.<\/p>\n\n\n\n<p>\ud83d\udca1 <strong>Recommended setting:<\/strong> For most deployments, keep at 0 for immediate cleanup. On networks with occasional packet loss, set to 5-10 seconds for a small grace window.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\ud83d\udda5\ufe0f-ss-sip-no-timer-reinvite-interval-non-timer-sip-caller-limit\">\ud83d\udda5\ufe0f SS_SIP_NO_TIMER_REINVITE_INTERVAL \u2014 Non-Timer SIP Caller Limit<\/h3>\n\n\n\n<p>\ud83d\udcf1 Not all SIP endpoints support session timers. <strong>SS_SIP_NO_TIMER_REINVITE_INTERVAL<\/strong> handles this scenario by setting a maximum conversation time for SIP callers that do NOT support the &#8220;timer&#8221; feature.<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><th class=\"has-text-align-left\" data-align=\"left\">Attribute<\/th><th class=\"has-text-align-left\" data-align=\"left\">Value<\/th><\/tr><tr><td>\ud83d\udccc Parameter Name<\/td><td>SS_SIP_NO_TIMER_REINVITE_INTERVAL<\/td><\/tr><tr><td>\ud83d\udd22 Default Value<\/td><td>7200 seconds (2 hours)<\/td><\/tr><tr><td>\ud83d\udcd0 Unit<\/td><td>Seconds<\/td><\/tr><tr><td>\ud83d\udcdd Description<\/td><td>If SIP caller doesn&#8217;t support &#8220;timer&#8221;, softswitch will stop the call when the time is up<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p>\ud83d\udd10 <strong>Critical function:<\/strong> Since non-timer SIP callers cannot respond to session refresh requests, VOS3000 cannot actively verify if the call is still alive. The only protection is a hard timeout \u2014 once the call duration exceeds this value, VOS3000 forcibly terminates it.<\/p>\n\n\n\n<p>\u26a0\ufe0f <strong>Default of 7200s (2 hours):<\/strong> This means a zombie call from a non-timer endpoint could persist for up to 2 hours. For high-value routes, consider lowering this to 3600s (1 hour) or even 1800s (30 minutes).<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\ud83d\udccb-how-vos-3000-sip-session-timer-works-complete-flow\">\ud83d\udccb How VOS3000 SIP Session Timer Works \u2014 Complete Flow<\/h2>\n\n\n\n<p>\ud83d\udd04 Understanding the full session timer flow is essential for proper configuration. Here&#8217;s exactly what happens during a call:<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\ud83c\udfaf-scenario-a-caller-supports-session-timer\">\ud83c\udfaf Scenario A: Caller SUPPORTS Session Timer<\/h3>\n\n\n\n<pre class=\"wp-block-preformatted\">\ud83d\udcde Call Established (200 OK)\n    \u2502\n    \u251c\u2500\u2500 VOS3000 starts TTL countdown (SS_SIP_SESSION_TTL = 600s)\n    \u2502\n    \u251c\u2500\u2500 At TTL\/Segment = 300s \u2500\u2500\u25ba VOS3000 sends re-INVITE\/UPDATE\n    \u2502   \u251c\u2500\u2500 \u2705 200 OK received \u2192 Session confirmed, timer resets\n    \u2502   \u2514\u2500\u2500 \u274c No response \u2192 Retry at next segment\n    \u2502\n    \u251c\u2500\u2500 At TTL = 600s \u2500\u2500\u25ba Final check\n    \u2502   \u251c\u2500\u2500 \u2705 200 OK received \u2192 Session confirmed, timer resets\n    \u2502   \u2514\u2500\u2500 \u274c No response \u2192 Call terminated (BYE sent)\n    \u2502       \u2514\u2500\u2500 If EARLY_HANGUP &gt; 0 \u2192 Wait X seconds, then BYE\n    \u2502\n    \u2514\u2500\u2500 \ud83d\udd01 Cycle repeats for duration of call\n<\/pre>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\ud83c\udfaf-scenario-b-caller-does-not-support-session-timer\">\ud83c\udfaf Scenario B: Caller Does NOT Support Session Timer<\/h3>\n\n\n\n<pre class=\"wp-block-preformatted\">\ud83d\udcde Call Established (200 OK \u2014 no Session-Expires header)\n    \u2502\n    \u251c\u2500\u2500 VOS3000 detects no timer support\n    \u2502\n    \u251c\u2500\u2500 No re-INVITE\/UPDATE messages sent\n    \u2502\n    \u251c\u2500\u2500 Call continues until...\n    \u2502   \u251c\u2500\u2500 \ud83d\udcf1 Normal BYE from either party, OR\n    \u2502   \u2514\u2500\u2500 \u23f0 Duration exceeds SS_SIP_NO_TIMER_REINVITE_INTERVAL (7200s)\n    \u2502       \u2514\u2500\u2500 VOS3000 forcibly terminates call (BYE sent)\n    \u2502\n    \u2514\u2500\u2500 \u274c No active session detection possible\n<\/pre>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\ud83d\udd27-step-by-step-vos-3000-sip-session-timer-configuration\">\ud83d\udd27 Step-by-Step VOS3000 SIP Session Timer Configuration<\/h2>\n\n\n\n<p>\ud83d\udda5\ufe0f Follow these steps to configure the VOS3000 SIP session timer parameters:<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"step-1-navigate-to-sip-parameters-\ud83d\udccb\">Step 1: Navigate to SIP Parameters \ud83d\udccb<\/h3>\n\n\n\n<ol class=\"wp-block-list\">\n<li>\ud83d\udd10 Log in to VOS3000 Client<\/li>\n\n\n\n<li>\ud83d\udccc Navigate: <strong>Operation management \u2192 Softswitch management \u2192 Additional settings \u2192 SIP parameter<\/strong><\/li>\n\n\n\n<li>\ud83d\udd0d Locate the session timer parameters in the parameter list<\/li>\n<\/ol>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"step-2-configure-ss-sip-session-ttl-\u23f1\ufe0f\">Step 2: Configure SS_SIP_SESSION_TTL \u23f1\ufe0f<\/h3>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><th class=\"has-text-align-left\" data-align=\"left\">Deployment Type<\/th><th class=\"has-text-align-left\" data-align=\"left\">Recommended TTL<\/th><th class=\"has-text-align-left\" data-align=\"left\">Rationale<\/th><\/tr><tr><td>\ud83c\udfe2 Standard enterprise<\/td><td>600s (default)<\/td><td>\u2705 Good balance of detection and overhead<\/td><\/tr><tr><td>\ud83d\udcde High-volume wholesale<\/td><td>300s \u2013 600s<\/td><td>\ud83d\udd27 Faster zombie detection on busy routes<\/td><\/tr><tr><td>\ud83c\udf10 Unstable networks<\/td><td>180s \u2013 300s<\/td><td>\ud83d\udce1 Quick detection of dropped calls<\/td><\/tr><tr><td>\ud83d\udee1\ufe0f Premium routes<\/td><td>900s \u2013 1800s<\/td><td>\ud83d\udd10 Less signaling overhead, longer calls OK<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"step-3-set-ss-sip-session-update-segment-\ud83d\udd04\">Step 3: Set SS_SIP_SESSION_UPDATE_SEGMENT \ud83d\udd04<\/h3>\n\n\n\n<p>\ud83d\udcca Choose the segment value based on your network reliability:<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><th class=\"has-text-align-left\" data-align=\"left\">Segment Value<\/th><th class=\"has-text-align-left\" data-align=\"left\">TTL=600 Interval<\/th><th class=\"has-text-align-left\" data-align=\"left\">Retry Count<\/th><th class=\"has-text-align-left\" data-align=\"left\">Best For<\/th><\/tr><tr><td>2 (default)<\/td><td>300s<\/td><td>2 attempts<\/td><td>\u2705 Most deployments<\/td><\/tr><tr><td>3<\/td><td>200s<\/td><td>3 attempts<\/td><td>\ud83d\udd27 Moderate reliability<\/td><\/tr><tr><td>5<\/td><td>120s<\/td><td>5 attempts<\/td><td>\ud83d\udce1 Flaky connections<\/td><\/tr><tr><td>8<\/td><td>75s<\/td><td>8 attempts<\/td><td>\u26a0\ufe0f Very unstable nets<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"step-4-configure-early-hangup-\u23f0\">Step 4: Configure Early Hangup \u23f0<\/h3>\n\n\n\n<p>\ud83d\udd12 Set <strong>SS_SIP_SESSION_TIMEOUT_EARLY_HANGUP<\/strong> based on your tolerance for ghost calls:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u2705 <strong>0 seconds (default):<\/strong> Immediate hangup \u2014 zero tolerance for zombie calls<\/li>\n\n\n\n<li>\ud83d\udd27 <strong>5-10 seconds:<\/strong> Small grace window for momentary network blips<\/li>\n\n\n\n<li>\u26a0\ufe0f <strong>30+ seconds:<\/strong> Not recommended \u2014 defeats the purpose of session timers<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"step-5-adjust-non-timer-caller-limit-\ud83d\udcf1\">Step 5: Adjust Non-Timer Caller Limit \ud83d\udcf1<\/h3>\n\n\n\n<p>\ud83c\udfaf Set <strong>SS_SIP_NO_TIMER_REINVITE_INTERVAL<\/strong> based on your risk tolerance:<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><th class=\"has-text-align-left\" data-align=\"left\">Setting<\/th><th class=\"has-text-align-left\" data-align=\"left\">Duration<\/th><th class=\"has-text-align-left\" data-align=\"left\">Risk Level<\/th><th class=\"has-text-align-left\" data-align=\"left\">Use Case<\/th><\/tr><tr><td>7200s (default)<\/td><td>2 hours<\/td><td>\u26a0\ufe0f Medium<\/td><td>Standard VoIP operations<\/td><\/tr><tr><td>3600s<\/td><td>1 hour<\/td><td>\ud83d\udd27 Low-Medium<\/td><td>Wholesale termination<\/td><\/tr><tr><td>1800s<\/td><td>30 minutes<\/td><td>\u2705 Low<\/td><td>High-value premium routes<\/td><\/tr><tr><td>900s<\/td><td>15 minutes<\/td><td>\ud83d\udee1\ufe0f Very Low<\/td><td>Maximum protection<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\ud83d\udcca-complete-vos-3000-sip-session-timer-parameter-reference\">\ud83d\udcca Complete VOS3000 SIP Session Timer Parameter Reference<\/h2>\n\n\n\n<p>\ud83d\udccb Here&#8217;s the full reference table combining all session timer parameters from the official VOS3000 2.1.9.07 manual:<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><th class=\"has-text-align-left\" data-align=\"left\">Parameter<\/th><th class=\"has-text-align-left\" data-align=\"left\">Default<\/th><th class=\"has-text-align-left\" data-align=\"left\">Unit<\/th><th class=\"has-text-align-left\" data-align=\"left\">Range<\/th><th class=\"has-text-align-left\" data-align=\"left\">Purpose<\/th><\/tr><tr><td>SS_SIP_SESSION_TTL<\/td><td>600<\/td><td>Seconds<\/td><td>\u2014<\/td><td>Session expiry detection interval<\/td><\/tr><tr><td>SS_SIP_SESSION_UPDATE_SEGMENT<\/td><td>2<\/td><td>Count<\/td><td>2\u201310<\/td><td>Re-INVITE interval divider<\/td><\/tr><tr><td>SS_SIP_SESSION_TIMEOUT_EARLY_HANGUP<\/td><td>0<\/td><td>Seconds<\/td><td>\u2014<\/td><td>Grace period before early hangup<\/td><\/tr><tr><td>SS_SIP_NO_TIMER_REINVITE_INTERVAL<\/td><td>7200<\/td><td>Seconds<\/td><td>\u2014<\/td><td>Max call time for non-timer UAs<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\ud83d\udee1\ufe0f-common-vos-3000-sip-session-timer-problems-and-solutions\">\ud83d\udee1\ufe0f Common VOS3000 SIP Session Timer Problems and Solutions<\/h2>\n\n\n\n<p>\u26a0\ufe0f Even with proper configuration, session timer issues can arise. Here are the most common problems and their fixes:<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\u274c-problem-1-calls-dropping-every-5-minutes\">\u274c Problem 1: Calls Dropping Every 5 Minutes<\/h3>\n\n\n\n<p>\ud83d\udd0d <strong>Symptom:<\/strong> Active calls are being terminated at exactly the re-INVITE interval.<\/p>\n\n\n\n<p>\ud83d\udca1 <strong>Cause:<\/strong> The far-end SIP device does not properly respond to re-INVITE or UPDATE messages. The VOS3000 SIP session timer interprets the lack of response as a dead call.<\/p>\n\n\n\n<p>\u2705 <strong>Solutions:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\ud83d\udd27 Increase SS_SIP_SESSION_TTL to give more time per cycle<\/li>\n\n\n\n<li>\ud83d\udd04 Reduce SS_SIP_SESSION_UPDATE_SEGMENT for fewer but longer intervals<\/li>\n\n\n\n<li>\ud83d\udce1 Verify the far-end device supports RFC 4028 session timers<\/li>\n\n\n\n<li>\ud83d\udcde Check if the far-end is behind a SIP ALG that drops re-INVITEs \u2014 see our <a href=\"https:\/\/multahost.com\/blog\/vos3000-sip-debug-guide\/\">SIP debug guide<\/a><\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\u274c-problem-2-ultra-long-bills-from-zombie-calls\">\u274c Problem 2: Ultra-Long Bills from Zombie Calls<\/h3>\n\n\n\n<p>\ud83d\udd0d <strong>Symptom:<\/strong> CDR records show calls lasting hours beyond actual conversation time.<\/p>\n\n\n\n<p>\ud83d\udca1 <strong>Cause:<\/strong> The SIP caller does not support session timers, and SS_SIP_NO_TIMER_REINVITE_INTERVAL is too high.<\/p>\n\n\n\n<p>\u2705 <strong>Solutions:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u23f1\ufe0f Reduce SS_SIP_NO_TIMER_REINVITE_INTERVAL from 7200 to 1800 or lower<\/li>\n\n\n\n<li>\ud83d\udd10 Ensure SS_SIP_SESSION_TIMEOUT_EARLY_HANGUP is set to 0 (immediate cleanup)<\/li>\n\n\n\n<li>\ud83d\udcca Monitor CDR records for abnormally long calls \u2014 use our <a href=\"https:\/\/multahost.com\/blog\/vos3000-cdr-billing-discrepancy\/\">CDR billing discrepancy guide<\/a><\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\u274c-problem-3-excessive-signaling-overhead\">\u274c Problem 3: Excessive Signaling Overhead<\/h3>\n\n\n\n<p>\ud83d\udd0d <strong>Symptom:<\/strong> High CPU usage on VOS3000 server, excessive SIP signaling traffic.<\/p>\n\n\n\n<p>\ud83d\udca1 <strong>Cause:<\/strong> SS_SIP_SESSION_UPDATE_SEGMENT is set too high, causing frequent re-INVITEs.<\/p>\n\n\n\n<p>\u2705 <strong>Solutions:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\ud83d\udcca Reduce SS_SIP_SESSION_UPDATE_SEGMENT to 2 (default) for fewer refresh attempts<\/li>\n\n\n\n<li>\u23f1\ufe0f Increase SS_SIP_SESSION_TTL to 900 or 1800 for longer cycles<\/li>\n\n\n\n<li>\ud83d\udd27 Balance detection speed against signaling load<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\ud83d\udca1-vos-3000-sip-session-timer-best-practices\">\ud83d\udca1 VOS3000 SIP Session Timer Best Practices<\/h2>\n\n\n\n<p>\ud83c\udfaf Follow these best practices to get the most from your VOS3000 SIP session timer configuration:<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><th class=\"has-text-align-left\" data-align=\"left\">Best Practice<\/th><th class=\"has-text-align-left\" data-align=\"left\">Recommendation<\/th><th class=\"has-text-align-left\" data-align=\"left\">Reason<\/th><\/tr><tr><td>\ud83c\udfaf Start with defaults<\/td><td>TTL=600, Segment=2<\/td><td>Proven balance for most deployments<\/td><\/tr><tr><td>\ud83d\udcca Monitor CDRs<\/td><td>Check for abnormally long calls weekly<\/td><td>Detects zombie calls early<\/td><\/tr><tr><td>\ud83d\udd12 Lower non-timer limit<\/td><td>Set NO_TIMER to 1800\u20133600<\/td><td>Reduces risk from non-RFC 4028 endpoints<\/td><\/tr><tr><td>\ud83d\udd04 Test before production<\/td><td>Verify with SIP debug tools<\/td><td>Avoids unexpected call drops<\/td><\/tr><tr><td>\ud83d\udcde Verify endpoint support<\/td><td>Check Session-Expires in SIP INVITE<\/td><td>Confirms timer negotiation works<\/td><\/tr><tr><td>\ud83d\udee1\ufe0f Keep early hangup at 0<\/td><td>Unless network is very unstable<\/td><td>Immediate cleanup is safer<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p>\ud83d\udca1 <strong>Pro tip:<\/strong> The VOS3000 SIP session timer works hand-in-hand with your <a href=\"https:\/\/multahost.com\/blog\/vos3000-max-call-duration\/\">max call duration<\/a> settings. While session timers actively detect dead calls, the max call duration parameter enforces a hard limit on all calls regardless of their state. Configure both for maximum protection.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\ud83d\udd04-vos-3000-sip-session-timer-and-sip-call-flow-interaction\">\ud83d\udd04 VOS3000 SIP Session Timer and SIP Call Flow Interaction<\/h2>\n\n\n\n<p>\ud83d\udce1 The session timer operates within the broader SIP call flow. Understanding how it interacts with other SIP messages is critical:<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">\ud83d\udcf1 SIP Call Flow with Session Timer:\n\nCaller \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500 VOS3000 \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500 Called Party\n  \u2502                              \u2502                              \u2502\n  \u2502\u2500\u2500\u2500\u2500 INVITE \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u25ba\u2502\u2500\u2500\u2500\u2500 INVITE \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u25ba\u2502\n  \u2502   (Session-Expires: 600)    \u2502   (Session-Expires: 600)    \u2502\n  \u2502                              \u2502                              \u2502\n  \u2502\u25c4\u2500\u2500\u2500 200 OK \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2502\u25c4\u2500\u2500\u2500 200 OK \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2502\n  \u2502   (Session-Expires: 600)    \u2502   (Session-Expires: 600)    \u2502\n  \u2502                              \u2502                              \u2502\n  \u2502       ... call in progress ...                              \u2502\n  \u2502                              \u2502                              \u2502\n  \u2502      \u250c\u2500 TTL\/Segment timer \u2500\u2500\u2510                              \u2502\n  \u2502      \u2502  (300s elapsed)      \u2502                              \u2502\n  \u2502      \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518                              \u2502\n  \u2502                              \u2502                              \u2502\n  \u2502\u25c4\u2500\u2500\u2500 re-INVITE\/UPDATE \u2500\u2500\u2500\u2500\u2500\u2500\u2502\u2500\u2500\u2500\u2500 re-INVITE\/UPDATE \u2500\u2500\u2500\u2500\u2500\u2500\u25ba\u2502\n  \u2502                              \u2502                              \u2502\n  \u2502\u2500\u2500\u2500\u2500 200 OK \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u25ba\u2502\u25c4\u2500\u2500\u2500 200 OK \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2502\n  \u2502                              \u2502                              \u2502\n  \u2502       ... timer resets ...                                  \u2502\n  \u2502                              \u2502                              \u2502\n  \u274c If no 200 OK response:                                     \u2502\n  \u2502                              \u2502\u2500\u2500\u2500\u2500 BYE \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u25ba\u2502\n  \u2502\u25c4\u2500\u2500\u2500 BYE \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2502                              \u2502\n<\/pre>\n\n\n\n<p>\ud83d\udd27 For a deeper understanding of how session timers fit into the complete SIP call lifecycle, see our comprehensive <a href=\"https:\/\/multahost.com\/blog\/vos3000-sip-call-flow\/\">SIP call flow guide<\/a>.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\ud83d\udd10-verifying-vos-3000-sip-session-timer-operation\">\ud83d\udd10 Verifying VOS3000 SIP Session Timer Operation<\/h2>\n\n\n\n<p>\ud83d\udcdd After configuration, verify that session timers are working correctly:<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"using-sip-debug-to-confirm-timer-negotiation-\ud83d\udd0d\">Using SIP Debug to Confirm Timer Negotiation \ud83d\udd0d<\/h3>\n\n\n\n<pre class=\"wp-block-preformatted\"># Check SIP INVITE for Session-Expires header\n# This confirms the caller supports session timers\n\nINVITE sip:destination@example.com SIP\/2.0\nVia: SIP\/2.0\/UDP 192.168.1.100:5060\nFrom: &lt;sip:caller@example.com&gt;;tag=abc123\nTo: &lt;sip:destination@example.com&gt;\nCall-ID: session-timer-test@example.com\nCSeq: 1 INVITE\nSession-Expires: 600        &lt;-- \ud83d\udd11 Session timer negotiated!\nMin-SE: 90                  &lt;-- \ud83d\udd11 Minimum session interval\nContact: &lt;sip:caller@192.168.1.100:5060&gt;\nContent-Type: application\/sdp\nContent-Length: ...\n\n# If no Session-Expires header appears,\n# the caller does NOT support session timers\n# VOS3000 will use SS_SIP_NO_TIMER_REINVITE_INTERVAL instead\n<\/pre>\n\n\n\n<p>\ud83d\udcde Need help debugging SIP signaling? Check our <a href=\"https:\/\/multahost.com\/blog\/vos3000-sip-debug-guide\/\">SIP debug guide<\/a> for step-by-step Wireshark capture instructions.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\u2753-frequently-asked-questions\">\u2753 Frequently Asked Questions<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\u2753-what-is-the-default-vos-3000-sip-session-timer-value\">\u2753 What is the default VOS3000 SIP session timer value?<\/h3>\n\n\n\n<p>\u23f1\ufe0f The default VOS3000 SIP session timer value is <strong>600 seconds (10 minutes)<\/strong>, configured via the <strong>SS_SIP_SESSION_TTL<\/strong> parameter. This means VOS3000 will attempt to verify call connectivity every 600 seconds divided by the SS_SIP_SESSION_UPDATE_SEGMENT value (default 2), resulting in a re-INVITE every 300 seconds.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\u2753-how-does-vos-3000-handle-sip-callers-that-do-not-support-session-timers\">\u2753 How does VOS3000 handle SIP callers that do not support session timers?<\/h3>\n\n\n\n<p>\ud83d\udcf1 When a SIP caller does not support the &#8220;timer&#8221; feature (no Session-Expires header in INVITE\/200 OK), VOS3000 cannot send re-INVITE or UPDATE messages to verify the call. Instead, it uses the <strong>SS_SIP_NO_TIMER_REINVITE_INTERVAL<\/strong> parameter (default: 7200 seconds \/ 2 hours) as a hard limit. When the call duration exceeds this value, VOS3000 forcibly terminates the call.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\u2753-can-i-set-ss-sip-session-update-segment-to-1\">\u2753 Can I set SS_SIP_SESSION_UPDATE_SEGMENT to 1?<\/h3>\n\n\n\n<p>\u274c No. The valid range for SS_SIP_SESSION_UPDATE_SEGMENT is <strong>2 to 10<\/strong>. A value of 1 would mean only one attempt to verify the session, which provides no retry capability. The minimum of 2 ensures at least one re-INVITE and one retry opportunity within the TTL period.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\u2753-what-happens-when-vos-3000-sip-session-timer-detects-a-dead-call\">\u2753 What happens when VOS3000 SIP session timer detects a dead call?<\/h3>\n\n\n\n<p>\ud83d\udd12 When VOS3000 sends a re-INVITE or UPDATE and receives no 200 OK confirmation within the TTL period, it considers the call finished. VOS3000 then sends a <strong>BYE message<\/strong> to terminate the call. If <strong>SS_SIP_SESSION_TIMEOUT_EARLY_HANGUP<\/strong> is set to a value greater than 0, VOS3000 will wait that many seconds before sending the BYE, giving the endpoint a brief grace period to recover.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\u2753-is-the-vos-3000-sip-session-timer-compliant-with-rfc-4028\">\u2753 Is the VOS3000 SIP session timer compliant with RFC 4028?<\/h3>\n\n\n\n<p>\u2705 Yes. The VOS3000 SIP session timer implementation follows <strong>RFC 4028 \u2014 Session Timers in the Session Initiation Protocol<\/strong>. VOS3000 supports the Session-Expires header, re-INVITE and UPDATE refresh methods, and proper session timer negotiation as defined in the RFC. Refer to the official VOS3000 documentation at <a href=\"https:\/\/www.vos3000.com\/downloads.php\" target=\"_blank\" rel=\"noopener\">vos3000.com<\/a> for detailed compliance information.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\u2753-should-i-enable-ss-sip-session-timeout-early-hangup\">\u2753 Should I enable SS_SIP_SESSION_TIMEOUT_EARLY_HANGUP?<\/h3>\n\n\n\n<p>\ud83d\udca1 It depends on your network conditions. The default value of <strong>0 (disabled)<\/strong> is recommended for most deployments because it provides immediate cleanup of dead sessions. If your network experiences occasional momentary packet loss that could cause a re-INVITE response to be delayed by a few seconds, you can set it to <strong>5-10 seconds<\/strong> for a small grace window. Values above 30 seconds are not recommended as they undermine the purpose of session timers.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\u2753-how-does-vos-3000-sip-session-timer-prevent-ultra-long-bills\">\u2753 How does VOS3000 SIP session timer prevent ultra-long bills?<\/h3>\n\n\n\n<p>\ud83d\udee1\ufe0f Ultra-long bills occur when calls remain in &#8220;connected&#8221; state after the actual conversation has ended \u2014 typically due to network failures, NAT timeouts, or endpoint crashes that prevent proper BYE messages. The VOS3000 SIP session timer prevents this by <strong>actively probing<\/strong> the call at regular intervals. If the far-end cannot confirm the session is still alive, VOS3000 terminates it. For non-timer endpoints, the SS_SIP_NO_TIMER_REINVITE_INTERVAL enforces a hard maximum duration. Combined with proper <a href=\"https:\/\/multahost.com\/blog\/vos3000-billing-system\/\">billing system<\/a> configuration, this effectively eliminates zombie-call billing.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\ud83d\udcde-need-expert-help-with-vos-3000-sip-session-timer\">\ud83d\udcde Need Expert Help with VOS3000 SIP Session Timer?<\/h2>\n\n\n\n<p>\ud83d\udd27 Configuring the VOS3000 SIP session timer correctly is critical for preventing revenue loss from zombie calls and ultra-long bills. If you need expert assistance with your VOS3000 deployment, our team is ready to help.<\/p>\n\n\n\n<p>\ud83d\udcac <strong>WhatsApp:<\/strong> <a href=\"https:\/\/wa.me\/8801911119966\" target=\"_blank\" rel=\"noopener\">+8801911119966<\/a> \u2014 Get instant support for VOS3000 SIP session timer configuration, RFC 4028 compliance, and VoIP network optimization.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\ud83d\udcda-related-resources\">\ud83d\udcda Related Resources<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\ud83d\udd17 <a href=\"https:\/\/multahost.com\/blog\/vos3000-session-timer\/\">VOS3000 Session Timer<\/a> \u2014 Complete session timer overview<\/li>\n\n\n\n<li>\ud83d\udd17 <a href=\"https:\/\/multahost.com\/blog\/vos3000-max-call-duration\/\">VOS3000 Max Call Duration<\/a> \u2014 Hard call duration limits<\/li>\n\n\n\n<li>\ud83d\udd17 <a href=\"https:\/\/multahost.com\/blog\/vos3000-sip-call-flow\/\">VOS3000 SIP Call Flow<\/a> \u2014 Full SIP signaling lifecycle<\/li>\n\n\n\n<li>\ud83d\udd17 <a href=\"https:\/\/multahost.com\/blog\/vos3000-sip-debug-guide\/\">VOS3000 SIP Debug Guide<\/a> \u2014 Troubleshoot SIP signaling issues<\/li>\n\n\n\n<li>\ud83d\udd17 <a href=\"https:\/\/multahost.com\/blog\/vos3000-parameter-description\/\">VOS3000 Parameter Description<\/a> \u2014 All parameter reference<\/li>\n\n\n\n<li>\ud83d\udd17 <a href=\"https:\/\/multahost.com\/blog\/vos3000-cdr-billing-discrepancy\/\">VOS3000 CDR Billing Discrepancy<\/a> \u2014 Fix billing accuracy issues<\/li>\n\n\n\n<li>\ud83d\udd17 <a href=\"https:\/\/multahost.com\/blog\/vos3000-billing-system\/\">VOS3000 Billing System<\/a> \u2014 Complete billing configuration<\/li>\n\n\n\n<li>\ud83d\udd17 <a href=\"https:\/\/multahost.com\/blog\/vos3000-system-parameters\/\">VOS3000 System Parameters<\/a> \u2014 System-level configuration<\/li>\n\n\n\n<li>\ud83d\udd17 <a href=\"https:\/\/multahost.com\/blog\/vos3000-sip-session\/\">VOS3000 SIP Session<\/a> \u2014 SIP session management<\/li>\n<\/ul>\n\n\n\n<p>\ud83d\udcde Still have questions about the VOS3000 SIP session timer? Reach out on WhatsApp at <strong>+8801911119966<\/strong> \u2014 we provide professional VOS3000 installation, configuration, and support services worldwide. \ud83c\udf10<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\ud83d\udcde-need-call-center-setup-support\">\ud83d\udcde Need Professional VOS3000 Setup Support?<\/h2>\n\n\n\n<p>For professional VOS3000 installations and deployment, VOS3000 Server Rental Solution:<\/p>\n\n\n\n<p>\ud83d\udcf1 <strong>WhatsApp:<\/strong> <a href=\"https:\/\/wa.me\/8801911119966\" target=\"_blank\" rel=\"noopener\">+8801911119966<\/a><br>\ud83c\udf10 <strong>Website:<\/strong> <a href=\"https:\/\/www.vos3000.com\" target=\"_blank\" rel=\"noopener\">www.vos3000.com<\/a><br>\ud83c\udf10 <strong>Blog:<\/strong> <a href=\"https:\/\/multahost.com\/blog\">multahost.com\/blog<\/a><br>\ud83d\udce5 <strong>Downloads:<\/strong> <a href=\"https:\/\/www.vos3000.com\/downloads.php\" target=\"_blank\" rel=\"noopener\">VOS3000 Downloads<\/a><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td><img data-recalc-dims=\"1\" height=\"540\" width=\"809\" decoding=\"async\" src=\"data:image\/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==\" alt=\"VOS3000 SIP Authentication Retry, VOS3000 SIP Early Hangup, VOS3000 SIP Session Timer Refresh, VOS3000 Non-Timer Endpoint Safety, VOS3000 SIP NAT Keepalive\" title=\"\" class=\"lazyload\" data-src=\"https:\/\/i0.wp.com\/multahost.com\/blog\/wp-content\/uploads\/2026\/04\/VOS3000-SIP-Authentication-Retry-VOS3000-SIP-Early-Hangup-VOS3000-SIP-Session-Timer-Refresh-VOS3000-Non-Timer-Endpoint-Safety-VOS3000-SIP-NAT-Keepalive-3.png?resize=809%2C540\"><\/td><td><img data-recalc-dims=\"1\" height=\"540\" width=\"809\" decoding=\"async\" src=\"data:image\/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==\" alt=\"VOS3000 SIP Authentication Retry, VOS3000 SIP Early Hangup, VOS3000 SIP Session Timer Refresh, VOS3000 Non-Timer Endpoint Safety, VOS3000 SIP NAT Keepalive\" title=\"\" class=\"lazyload\" data-src=\"https:\/\/i0.wp.com\/multahost.com\/blog\/wp-content\/uploads\/2026\/04\/VOS3000-SIP-Authentication-Retry-VOS3000-SIP-Early-Hangup-VOS3000-SIP-Session-Timer-Refresh-VOS3000-Non-Timer-Endpoint-Safety-VOS3000-SIP-NAT-Keepalive-3.png?resize=809%2C540\"><\/td><td><img data-recalc-dims=\"1\" height=\"540\" width=\"809\" decoding=\"async\" src=\"data:image\/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==\" alt=\"VOS3000 SIP Authentication Retry, VOS3000 SIP Early Hangup, VOS3000 SIP Session Timer Refresh, VOS3000 Non-Timer Endpoint Safety, VOS3000 SIP NAT Keepalive\" title=\"\" class=\"lazyload\" data-src=\"https:\/\/i0.wp.com\/multahost.com\/blog\/wp-content\/uploads\/2026\/04\/VOS3000-SIP-Authentication-Retry-VOS3000-SIP-Early-Hangup-VOS3000-SIP-Session-Timer-Refresh-VOS3000-Non-Timer-Endpoint-Safety-VOS3000-SIP-NAT-Keepalive-3.png?resize=809%2C540\"><\/td><\/tr><\/tbody><\/table><\/figure>\n","protected":false},"excerpt":{"rendered":"<p>VOS3000 SIP Session Timer: Powerful RFC 4028 Setup Guide \ud83d\udcde Are mysterious ghost calls and ultra-long bills draining your VoIP revenue? The VOS3000 SIP session timer is your first line of defense. Based on RFC 4028, this critical SIP protocol feature detects whether calls are still alive \u2014 and automatically hangs up dead sessions before [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":3118,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[2],"tags":[5193,5204,8259,8244,8257,8247,8267,8252,8265,8263,8266,8245,5194,8250,8242,8256,8237,8264,8261,8253,8240,8248,8255,8236,8235,5640,8234,7321,3981,7884,7861,2380,8246,7882,8249,8254,8262,8260,3758,5005,8238,3123,8239,5178,6256,8243,8258,8241,909,8251],"class_list":["post-3121","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-vos3000","tag-rfc-4028","tag-session-timer-negotiation","tag-sip-422-response","tag-sip-call-duration-limit","tag-sip-call-validation","tag-sip-connected-status-detection","tag-sip-connection-status","tag-sip-min-se-header","tag-sip-parameter-configuration","tag-sip-parameter-tuning","tag-sip-protocol-parameters","tag-sip-re-invite-interval","tag-sip-session-expiration","tag-sip-session-expires-header","tag-sip-session-refresh","tag-sip-session-timer-refresher","tag-sip-session-timer-setup","tag-sip-session-timer-troubleshooting","tag-sip-timer-default-values","tag-sip-timer-provisioning","tag-sip-timer-rfc-4028-compliance","tag-sip-update-message","tag-sip-zombie-call-prevention","tag-ss_sip_no_timer_reinvite_interval","tag-ss_sip_session_timeout_early_hangup","tag-ss_sip_session_ttl","tag-ss_sip_session_update_segment","tag-vos3000-additional-settings","tag-vos3000-billing-accuracy","tag-vos3000-call-cleanup","tag-vos3000-call-management","tag-vos3000-call-monitoring","tag-vos3000-early-hangup","tag-vos3000-ghost-call-prevention","tag-vos3000-hangup-detection","tag-vos3000-network-reliability","tag-vos3000-operation-management","tag-vos3000-session-keepalive","tag-vos3000-session-management","tag-vos3000-session-timeout","tag-vos3000-session-timer-configuration","tag-vos3000-sip-parameters","tag-vos3000-sip-reinvite","tag-vos3000-sip-session-timer","tag-vos3000-softswitch-management","tag-vos3000-softswitch-timer","tag-vos3000-trunk-timer","tag-vos3000-ultra-long-bills-prevention","tag-vos3000-voip-softswitch","tag-vos3000-voip-timer"],"acf":[],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"https:\/\/i0.wp.com\/multahost.com\/blog\/wp-content\/uploads\/2026\/04\/VOS3000-SIP-Authentication-Retry-VOS3000-SIP-Early-Hangup-VOS3000-SIP-Session-Timer-Refresh-VOS3000-Non-Timer-Endpoint-Safety-VOS3000-SIP-NAT-Keepalive-1.png?fit=1536%2C1024&ssl=1?v=1776647903","jetpack-related-posts":[{"id":3122,"url":"https:\/\/multahost.com\/blog\/vos3000-sip-no-timer-call-duration\/","url_meta":{"origin":3121,"position":0},"title":"VOS3000 SIP No Timer Call Duration: Important Maximum Limit Easy Guide","author":"king","date":"April 20, 2026","format":false,"excerpt":"Master VOS3000 SIP no timer call duration limit. Configure SS_SIP_NO_TIMER_REINVITE_INTERVAL to prevent runaway calls, protect billing accuracy, and stop zombie sessions.","rel":"","context":"In &quot;VOS3000 SIP&quot;","block_context":{"text":"VOS3000 SIP","link":"https:\/\/multahost.com\/blog\/category\/vos3000-sip\/"},"img":{"alt_text":"VOS3000 SIP Authentication Retry, VOS3000 SIP Early Hangup, VOS3000 SIP Session Timer Refresh, VOS3000 Non-Timer Endpoint Safety, VOS3000 SIP NAT Keepalive, VOS3000 SIP Resend Interval, VOS3000 SIP INVITE Timeout, VOS3000 SIP Call Progress Timeout, VOS3000 SIP Outbound Registration Parameters, VOS3000 SIP Privacy Header, VOS3000 SIP Routing Gateway Contact, VOS3000 SIP Publish Expire, VOS3000 SIP Display From, VOS3000 SIP Send Unregister","src":"https:\/\/i0.wp.com\/multahost.com\/blog\/wp-content\/uploads\/2026\/04\/VOS3000-SIP-Authentication-Retry-VOS3000-SIP-Early-Hangup-VOS3000-SIP-Session-Timer-Refresh-VOS3000-Non-Timer-Endpoint-Safety-VOS3000-SIP-NAT-Keepalive-2.png?fit=1200%2C800&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/multahost.com\/blog\/wp-content\/uploads\/2026\/04\/VOS3000-SIP-Authentication-Retry-VOS3000-SIP-Early-Hangup-VOS3000-SIP-Session-Timer-Refresh-VOS3000-Non-Timer-Endpoint-Safety-VOS3000-SIP-NAT-Keepalive-2.png?fit=1200%2C800&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/multahost.com\/blog\/wp-content\/uploads\/2026\/04\/VOS3000-SIP-Authentication-Retry-VOS3000-SIP-Early-Hangup-VOS3000-SIP-Session-Timer-Refresh-VOS3000-Non-Timer-Endpoint-Safety-VOS3000-SIP-NAT-Keepalive-2.png?fit=1200%2C800&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/multahost.com\/blog\/wp-content\/uploads\/2026\/04\/VOS3000-SIP-Authentication-Retry-VOS3000-SIP-Early-Hangup-VOS3000-SIP-Session-Timer-Refresh-VOS3000-Non-Timer-Endpoint-Safety-VOS3000-SIP-NAT-Keepalive-2.png?fit=1200%2C800&ssl=1&resize=700%2C400 2x, https:\/\/i0.wp.com\/multahost.com\/blog\/wp-content\/uploads\/2026\/04\/VOS3000-SIP-Authentication-Retry-VOS3000-SIP-Early-Hangup-VOS3000-SIP-Session-Timer-Refresh-VOS3000-Non-Timer-Endpoint-Safety-VOS3000-SIP-NAT-Keepalive-2.png?fit=1200%2C800&ssl=1&resize=1050%2C600 3x"},"classes":[]},{"id":2435,"url":"https:\/\/multahost.com\/blog\/vos3000-sip-session\/","url_meta":{"origin":3121,"position":1},"title":"VOS3000 SIP Session Timer: Complete Keep-Alive &amp; Session Management Important Guide","author":"king","date":"April 3, 2026","format":false,"excerpt":"Master VOS3000 SIP session timer and NAT keep-alive. 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