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VOS3000 QoS configuration is essential for ensuring superior voice quality in enterprise and carrier VoIP deployments. By properly marking SIP signaling and RTP media packets with DSCP (Differentiated Services Code Point) values, VOS3000 enables network infrastructure to prioritize voice traffic, reducing latency, jitter, and packet loss that degrade call quality. This comprehensive guide covers all QoS features based on official VOS3000 2.1.9.07 documentation.
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Reference: VOS3000 2.1.9.07 Manual, Section 4.1.4 (Page 214)
Quality of Service (QoS) in VoIP refers to the ability to prioritize voice traffic over data traffic on IP networks. Voice calls are highly sensitive to network conditions – even small amounts of latency, jitter, or packet loss can significantly degrade call quality. QoS mechanisms ensure voice packets receive preferential treatment.
| Metric | Voice Requirement | Impact if Exceeded | QoS Benefit |
|---|---|---|---|
| Latency | < 150ms one-way | Echo, talk-over, delayed response | Priority queuing reduces delay |
| Jitter | < 30ms variation | Choppy audio, robotic voice | Consistent queuing reduces variation |
| Packet Loss | < 1% | Clicks, pops, missing syllables | Priority treatment reduces drops |
| Bandwidth | ~30-90 kbps per call | Congestion, quality degradation | Guaranteed bandwidth allocation |
Reference: VOS3000 2.1.9.07 Manual, Section 4.1.4 (Page 214)
| Parameter | Default | Description | Applies To |
|---|---|---|---|
| SS_QOS_SIGNAL | 0xa0 | QoS marking for SIP signaling packets | SIP INVITE, REGISTER, BYE, etc. |
| SS_QOS_RTP | 0xa0 | QoS marking for RTP media packets | Voice/audio RTP streams |
The QoS parameters use hexadecimal values that correspond to the DSCP field in the IP header:
| Hex Value | Binary | DSCP Name | Typical Use | Priority Level |
|---|---|---|---|---|
| 0xb8 | 101110 | EF (Expedited Forwarding) | Voice RTP | Highest |
| 0xa0 | 101000 | CS5 (Class Selector 5) | Voice Signaling | High |
| 0x88 | 100010 | AF41 | Video Conferencing | Medium-High |
| 0x00 | 000000 | BE (Best Effort) | Regular Data | Default |
Reference: VOS3000 2.1.9.07 Manual, Section 4.1.4 (Page 214)
IP Header QoS Field Structure:
==============================
The Differentiated Services Field in IP header:
Bits: 0 1 2 3 4 5 6 7
+---+---+---+---+---+---+---+---+
| DSCP (6 bits) | ECN |
+---+---+---+---+---+---+---+---+
DSCP = Differentiated Services Code Point
ECN = Explicit Congestion Notification
VOS3000 Default: 0xa0
======================
Binary: 10100000
DSCP bits: 101000 (DSCP 40 = CS5)
ECN bits: 00
This means:
- DSCP Class Selector 5
- High priority for signaling
- No ECN marking
Wireshark Display:
==================
Differentiated Services Field: 0xa0 (DSCP: CS5, ECN: Not-ECT)
Reference: VOS3000 2.1.9.07 Manual, Section 4.1.4 (Page 214)
| Packet Type | Parameter | Default Value | Effect |
|---|---|---|---|
| SIP Signaling | SS_QOS_SIGNAL | 0xa0 (CS5) | Fast call setup, priority for INVITE/REGISTER |
| RTP Media | SS_QOS_RTP | 0xa0 (CS5) | Clear voice, reduced jitter and loss |
Navigate to: Operation management > Softswitch management > Additional settings > System parameter
Step-by-Step VOS3000 QoS Configuration: ======================================== 1. Access System Parameters: Navigation > Operation management > Softswitch management > Additional settings > System parameter 2. Locate QoS Parameters: Find: SS_QOS_SIGNAL Find: SS_QOS_RTP 3. Set Signaling QoS: Parameter: SS_QOS_SIGNAL Default: 0xa0 (CS5) Options: - 0xa0 = CS5 (recommended for SIP signaling) - 0x00 = Best Effort (no priority) - 0xb8 = EF (if signaling needs highest priority) 4. Set RTP Media QoS: Parameter: SS_QOS_RTP Default: 0xa0 (CS5) Options: - 0xb8 = EF (recommended for voice RTP) - 0xa0 = CS5 (acceptable for voice) - 0x00 = Best Effort (not recommended) 5. Apply Configuration: Click Apply to save changes 6. Verify with Packet Capture: Use Wireshark to confirm DSCP markings Recommended Values: =================== SS_QOS_SIGNAL = 0xa0 (CS5 - High priority signaling) SS_QOS_RTP = 0xb8 (EF - Highest priority voice)
QoS markings in VOS3000 are only effective if network infrastructure respects them. Here’s how to configure common network devices:
Cisco Router QoS Configuration Example: ======================================== ! Define class maps for voice traffic class-map match-any VOICE-SIGNAL match ip dscp cs5 class-map match-any VOICE-RTP match ip dscp ef ! Define policy map policy-map VOICE-POLICY class VOICE-RTP priority percent 30 set dscp ef class VOICE-SIGNAL bandwidth percent 5 set dscp cs5 ! Apply to interface interface GigabitEthernet0/0 service-policy output VOICE-POLICY ! Verify configuration show policy-map interface GigabitEthernet0/0
MikroTik RouterOS QoS Configuration: ===================================== # Create mangle rules to mark packets /ip firewall mangle add chain=postrouting protocol=udp dst-port=5060 action=mark-packet new-packet-mark=sip-signal passthrough=yes add chain=postrouting protocol=udp dst-port=10000-20000 action=mark-packet new-packet-mark=voice-rtp passthrough=yes # Create queue tree for prioritization /queue tree add name="voice-rtp" parent=global packet-mark=voice-rtp priority=1 max-limit=10M add name="sip-signal" parent=global packet-mark=sip-signal priority=2 max-limit=2M # Verify with packet sniffing /tool sniffer quick protocol=udp port=5060,10000-20000
Linux Traffic Control QoS Example: =================================== # Create root qdisc tc qdisc add dev eth0 root handle 1: htb default 20 # Create classes tc class add dev eth0 parent 1: classid 1:1 htb rate 100mbit tc class add dev eth0 parent 1:1 classid 1:10 htb rate 30mbit prio 1 # Voice tc class add dev eth0 parent 1:1 classid 1:20 htb rate 70mbit prio 2 # Data # Filter by DSCP tc filter add dev eth0 protocol ip parent 1:0 prio 1 u32 match ip dscp 0xb8 0xfc flowid 1:10 tc filter add dev eth0 protocol ip parent 1:0 prio 2 u32 match ip dscp 0xa0 0xfc flowid 1:10 # Verify tc -s qdisc show dev eth0
For effective QoS, all network elements must be configured:
| Network Element | Configuration Required | Impact if Not Configured |
|---|---|---|
| VOS3000 Server | Set SS_QOS_SIGNAL and SS_QOS_RTP | Packets sent without priority markings |
| Local Router | QoS policy matching DSCP values | Voice packets treated as data |
| WAN/MPLS | Provider respects DSCP or maps to MPLS EXP | Congestion causes voice quality issues |
| Remote Router | QoS policy on egress | Last-mile congestion affects quality |
| Endpoint | Send/receive marked packets | May mark differently, causing mismatch |
Verifying QoS with Wireshark: ============================= 1. Capture packets on VOS3000 server or network 2. Filter for SIP signaling: Display filter: sip 3. Filter for RTP media: Display filter: rtp 4. Check DSCP field: - Expand IP header in packet details - Look for "Differentiated Services Field" - Verify value matches configuration Expected Results: ================= SIP packets: Differentiated Services Field: 0xa0 (DSCP: CS5) RTP packets: Differentiated Services Field: 0xb8 (DSCP: EF) Wireshark Column Setup: ======================= Add "DSCP Value" column to quickly verify markings: 1. Right-click column header 2. Column Preferences 3. Add new column: "DSCP" with type "DSCP Value" Common Issues to Check: ======================= - Value shows 0x00 = QoS not applied - Value doesn't match configuration = Check parameter setting - Different values on different interfaces = Router rewriting DSCP
| Platform | Command | Purpose |
|---|---|---|
| Cisco | show policy-map interface | View QoS statistics |
| MikroTik | /queue tree print stats | View queue statistics |
| Linux | tc -s qdisc show | View traffic control stats |
| tcpdump | tcpdump -i eth0 -vv ip | View DSCP in packet headers |
| Problem | Symptom | Solution |
|---|---|---|
| Packets unmarked | Wireshark shows DSCP 0x00 | Verify SS_QOS parameters are set correctly |
| Router ignoring DSCP | Voice quality poor during congestion | Configure QoS policy on router |
| DSCP rewriting | Different DSCP on different network segments | Check router config for DSCP rewriting rules |
| Inconsistent marking | Some packets marked, some not | Check if media proxy is interfering |
| WAN provider strips DSCP | QoS works locally but not across WAN | Negotiate QoS with provider, use MPLS EXP |
QoS Troubleshooting Checklist: ============================== 1. Verify VOS3000 Configuration: ☐ Check SS_QOS_SIGNAL value ☐ Check SS_QOS_RTP value ☐ Verify parameters applied after change 2. Verify Packet Marking: ☐ Capture packets with Wireshark/tcpdump ☐ Check DSCP field in IP header ☐ Confirm values match configuration 3. Verify Network QoS: ☐ Check router QoS configuration ☐ Verify DSCP matching rules ☐ Check queue statistics for voice traffic 4. Verify End-to-End: ☐ Test from endpoint to VOS3000 ☐ Test through entire network path ☐ Check DSCP preservation at each hop 5. Performance Testing: ☐ Run voice quality tests under load ☐ Compare MOS scores with/without QoS ☐ Monitor latency, jitter, packet loss Best Practices: =============== - Document your QoS configuration - Test during peak traffic periods - Monitor QoS statistics regularly - Coordinate with WAN providers - Consider using separate VLAN for voice
For MPLS networks, DSCP values may need to be mapped to MPLS EXP bits:
| DSCP Value | MPLS EXP | Traffic Type |
|---|---|---|
| EF (0xb8) | 7 | Real-time voice |
| CS5 (0xa0) | 5 | Voice signaling |
| AF41 (0x88) | 4 | Interactive video |
| BE (0x00) | 0 | Best effort data |
The recommended DSCP value for voice RTP is EF (Expedited Forwarding, 0xb8), which provides the highest priority treatment. However, the VOS3000 default is CS5 (0xa0), which is also acceptable for voice. For best results in controlled networks, use 0xb8 for RTP and 0xa0 for SIP signaling.
No, QoS markings are generally not respected over the public internet. Most ISPs either ignore DSCP values or strip them entirely. QoS is effective only on networks you control (LAN, WAN with SLA, MPLS) or where you have agreement with the provider to honor markings.
QoS requires end-to-end configuration. Check: 1) VOS3000 parameters are set correctly, 2) Network devices are configured to match and prioritize marked packets, 3) There’s actual congestion for QoS to manage, 4) DSCP values aren’t being rewritten by intermediate devices.
VOS3000 QoS parameters (SS_QOS_SIGNAL and SS_QOS_RTP) apply globally to all calls processed by the softswitch. For per-endpoint QoS differentiation, you would need to implement QoS policies on network devices based on IP addresses or other criteria.
Generally, media (RTP) should have higher priority than signaling because it’s more sensitive to delay and jitter. A common approach is EF (0xb8) for RTP and CS5 (0xa0) for SIP signaling. However, VOS3000 defaults both to CS5, which works well in most scenarios.
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