QoS marking and queuing for voice

See also

Sources

1. 1
   DS domain boundary nodes must ensure that traffic entering the domain carries codepoints appropriate to the traffic and the domain, re-marking it where necessary.

   RFC 2474: Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers · Section 7.1 · Checked 2026-09-24
2. 2
   The Cisco Collaboration 14 PA treats the Internet as an unmanaged, non-QoS-enabled network. It relies on media resilience and rate adaptation there rather than on DSCP.

   Preferred Architecture for Cisco Collaboration 14 Enterprise On-Premises Deployments, CVD - Bandwidth Management · Bandwidth Management chapter, media resilience / unmanaged network section · Checked 2026-09-24
3. 3
   The Cisco Collaboration 14 PA treats PCs, Macs and mobile devices running Jabber as untrusted. It classifies their media and signaling by port ranges and re-marks with network access lists, while servers, gateways and video endpoints are trusted.

   Preferred Architecture for Cisco Collaboration 14 Enterprise On-Premises Deployments, CVD - Bandwidth Management · Bandwidth Management chapter, QoS trust and classification section · Checked 2026-09-24
4. 4
   In the Cisco Collaboration 14 PA, audio is marked EF, prioritized video AF41, opportunistic video (Jabber, MRA) AF42, and call signaling CS3.

   Preferred Architecture for Cisco Collaboration 14 Enterprise On-Premises Deployments, CVD - Bandwidth Management · Bandwidth Management chapter, QoS classification/marking tables · Checked 2026-09-24
5. 5
   Cisco warns that port-based classification of client media is not a fully secure method, because other applications can use the same ports and gain unintended priority.

   Preferred Architecture for Cisco Collaboration 14 Enterprise On-Premises Deployments, CVD - Bandwidth Management · Bandwidth Management chapter, Jabber classification caveat · Checked 2026-09-24
6. 6
   The Cisco Collaboration 14 PA places EF audio in a priority queue with a strict policer, sized for voice-only calls plus the audio portion of video calls. Video goes to CBWFQ with WRED, where AF42 is dropped before AF41.

   Preferred Architecture for Cisco Collaboration 14 Enterprise On-Premises Deployments, CVD - Bandwidth Management · Bandwidth Management chapter, WAN queuing section · Checked 2026-09-24
7. 7
   Cisco's Collaboration 14 Preferred Architecture recommends enforcing the QoS trust boundary at the network edge, at LAN access ingress, the WAN edge, or both.

   Preferred Architecture for Cisco Collaboration 14 Enterprise On-Premises Deployments, CVD - Bandwidth Management · Bandwidth Management chapter, QoS trust and classification section · Checked 2026-09-24
8. 8
   DSCP values of the form xxx000 are reserved as Class Selector codepoints for backward compatibility with IP Precedence.

   RFC 2474: Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers · Section 4.2.2.1 · Checked 2026-09-24
9. 9
   RFC 8622 moved away from CS1 for lower-effort traffic because domains that treat CS1 as an RFC 2474 Class Selector can forward it with higher precedence than best-effort traffic (priority inversion).

   RFC 8622: A Lower-Effort Per-Hop Behavior (LE PHB) for Differentiated Services · Section 6 (Recommended DSCP); Section 10 · Checked 2026-09-24
10. 10
    In Unified CM Release 15, custom DSCP values set in a SIP Profile override the matching clusterwide service parameter values for devices that use that profile.

    Feature Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs - Configure Flexible DSCP Marking and Video Promotion · Configure Flexible DSCP Marking and Video Promotion chapter, SIP Profile DSCP section · Checked 2026-09-24
11. 11
    The recommended codepoint for the Default PHB is 000000.

    RFC 2474: Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers · Section 4.1 · Checked 2026-09-24
12. 12
    The DS field uses six bits as the DSCP and replaces the IPv4 TOS octet and the IPv6 Traffic Class octet.

    RFC 2474: Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers · Section 3 (Differentiated Services Field Definition) · Checked 2026-09-24
13. 13
    RFC 7657 states that DSCP markings are not end to end in general, because each network chooses its own PHBs and DSCP mappings and may re-mark at its edge.

    RFC 7657: Differentiated Services (Diffserv) and Real-Time Communication · Diffserv architecture discussion (section number not confirmed) · Checked 2026-09-24
14. 14
    The recommended codepoint for the Expedited Forwarding PHB is 101110 (decimal 46).

    RFC 3246: An Expedited Forwarding PHB (Per-Hop Behavior) · Section 2.7 · Checked 2026-09-24
15. 15
    The EF PHB serves EF packets at a configured rate on an output interface regardless of the load from other traffic, to give low delay, jitter and loss.

    RFC 3246: An Expedited Forwarding PHB (Per-Hop Behavior) · Section 2.1 (Intuitive Description) · Checked 2026-09-24
16. 16
    The edge of a DS domain should strictly police all EF-marked packets to a rate negotiated with the adjacent upstream domain.

    RFC 3246: An Expedited Forwarding PHB (Per-Hop Behavior) · Section 3 (Security Considerations) · Checked 2026-09-24
17. 17
    Traffic conditioning at DS-domain ingress must ensure that packets carry an EF-mapped DSCP inside the domain only if they already had one on entry.

    RFC 3246: An Expedited Forwarding PHB (Per-Hop Behavior) · Section 3 (Security Considerations) · Checked 2026-09-24
18. 18
    RFC 3246 (March 2002) obsoletes RFC 2598 as the definition of the EF PHB.

    RFC 3246: An Expedited Forwarding PHB (Per-Hop Behavior) · Document header (Obsoletes: 2598) · Checked 2026-09-24
19. 19
    RFC 8622 updates RFC 4594 so that the Low-Priority Data class uses the LE codepoint 000001 (decimal 1) in place of CS1.

    RFC 8622: A Lower-Effort Per-Hop Behavior (LE PHB) for Differentiated Services · Document header (Updates: 4594, 8325); Section 10 (Changes to RFC 4594) · Checked 2026-09-24
20. 20
    RFC 7657 warns that giving packets in one 5-tuple different DSCPs makes reordering very likely, and advises limiting a single RTP stream to DSCPs within one AF class.

    RFC 7657: Differentiated Services (Diffserv) and Real-Time Communication · Section 6 (Guidelines) and the multiplexing discussion · Checked 2026-09-24
21. 21
    RFC 4594 assigns CS3 to the Broadcast Video service class, not to signaling.

    RFC 4594: Configuration Guidelines for DiffServ Service Classes · Section 2.3, Figure 3 · Checked 2026-09-24
22. 22
    RFC 4594 says CS6-marked flows from untrusted sources such as end-user devices should be dropped or re-marked at ingress to the DiffServ network.

    RFC 4594: Configuration Guidelines for DiffServ Service Classes · Section 3.2 (Network Control Service Class) · Checked 2026-09-24
23. 23
    RFC 4594 reserves CS7 (decimal 56) for future use and recommends dropping or re-marking CS7 packets at ingress to a DiffServ domain.

    RFC 4594: Configuration Guidelines for DiffServ Service Classes · Section 3.1 (Current Practice in the Internet) · Checked 2026-09-24
24. 24
    RFC 4594, the DiffServ service-class configuration guideline, is an Informational RFC published in August 2006, not a Standards Track specification.

    RFC 4594: Configuration Guidelines for DiffServ Service Classes · Document header (Category: Informational) · Checked 2026-09-24
25. 25
    RFC 4594 maps the Multimedia Conferencing service class to AF41, AF42 and AF43.

    RFC 4594: Configuration Guidelines for DiffServ Service Classes · Section 2.3, Figure 3 · Checked 2026-09-24
26. 26
    RFC 4594 maps the Signaling service class to CS5 (101000, decimal 40).

    RFC 4594: Configuration Guidelines for DiffServ Service Classes · Section 2.3, Figure 3; Section 4.2 (Signaling Service Class) · Checked 2026-09-24
27. 27
    RFC 4594 maps the Telephony service class to EF (101110, decimal 46).

    RFC 4594: Configuration Guidelines for DiffServ Service Classes · Section 2.3, Figure 3 (DSCP to Service Class Mapping) · Checked 2026-09-24
28. 28
    RFC 4594 says the Telephony service class should use the EF PHB and be configured with a priority queuing system.

    RFC 4594: Configuration Guidelines for DiffServ Service Classes · Section 1.4.1.1 and Section 4.1 (Telephony Service Class) · Checked 2026-09-24
29. 29
    RFC 4594 says telephony packet flows from untrusted sources such as end-user devices should be policed at ingress to the DiffServ network.

    RFC 4594: Configuration Guidelines for DiffServ Service Classes · Section 4.1 (Telephony Service Class) · Checked 2026-09-24
30. 30
    Signaling DSCP is not consistent across the sources. RFC 4594 and Teams use CS5, the Cisco Collaboration PA and Webex devices use CS3, and the Webex App uses CS0. A single signaling class-map will therefore not match all vendors.inferred

    RFC 4594: Configuration Guidelines for DiffServ Service Classes · Figure 3; compare ms-learn-qos-in-teams Step 3, cisco-pa-collab14-bandwidth-management marking table, cisco-help-b2exve-port-reference QoS section · Checked 2026-09-24
31. 31
    Teams QoS marking requires the 'Insert Quality of Service (QoS) markers for real-time media traffic' setting to be enabled globally in the Teams admin center, including for the Mac, mobile and Teams Phone clients that use hard-coded markings.

    Implement Quality of Service in Microsoft Teams · Step 4. Implement QoS settings, first and third bullets · Checked 2026-09-24
32. 32
    Microsoft recommends an initial Teams audio client source port range of 50000-50019 (TCP/UDP), marked DSCP 46 (EF).

    Implement Quality of Service in Microsoft Teams · Step 3. Choose initial port ranges for each media type, table 'Recommended initial port ranges' · Checked 2026-09-24
33. 33
    Microsoft recommends combining client-side DSCP marking with port-based ACL tagging on routers, so that devices unable to mark are still classified.

    Implement Quality of Service in Microsoft Teams · Step 2. Select a QoS implementation method > Best practice · Checked 2026-09-24
34. 34
    Microsoft's Teams QoS checklist runs in this order: confirm network readiness; select an implementation method; choose port ranges per media type; implement settings on clients, routers and media traffic; validate by analyzing traffic; manage source ports.

    Implement Quality of Service in Microsoft Teams · QoS implementation checklist, items 1-6 · Checked 2026-09-24
35. 35
    In Teams, administrators can adjust the media port ranges but cannot configure the DSCP markings.

    Implement Quality of Service in Microsoft Teams · Step 6. Manage source ports, closing Note · Checked 2026-09-24
36. 36
    Teams QoS policies created in a GPO do not take effect until Group Policy refreshes on the client, which can be forced with gpupdate /force.

    Implement Quality of Service (QoS) in Microsoft Teams desktop clients on Windows · Configuring DSCP markings using Group Policy, closing paragraph · Checked 2026-09-24
37. 37
    Teams Mac, iOS and Android clients use hard-coded markings that cannot be configured: EF for audio and AF41 for both video and application/screen sharing.

    Implement Quality of Service in Microsoft Teams · Step 3, bullet list after the port table; Step 4 bullets · Checked 2026-09-24
38. 38
    Microsoft says port-based tagging at the router works across platforms but marks traffic only at the WAN edge, not all the way to the client machine.

    Implement Quality of Service in Microsoft Teams · Step 2 > Port-based tagging at router · Checked 2026-09-24
39. 39
    Microsoft recommends an initial Teams application and screen sharing client source port range of 50040-50059, marked DSCP 18 (AF21).

    Implement Quality of Service in Microsoft Teams · Step 3, table 'Recommended initial port ranges' · Checked 2026-09-24
40. 40
    Teams calling and meetings signaling uses UDP source ports 50070-50089 marked DSCP 40 (CS5). Those ports are not currently configurable.

    Implement Quality of Service in Microsoft Teams · Step 3, table 'Recommended initial port ranges' and footnote · Checked 2026-09-24
41. 41
    Microsoft says the DSCP value must be present at both ends of a call, and advises capturing traffic, preferably at the network egress point, to check that the marking is not changed or stripped.

    Implement Quality of Service in Microsoft Teams · Step 5. Validate your QoS implementation · Checked 2026-09-24
42. 42
    Microsoft recommends an initial Teams video client source port range of 50020-50039, marked DSCP 34 (AF41).

    Implement Quality of Service in Microsoft Teams · Step 3, table 'Recommended initial port ranges' · Checked 2026-09-24
43. 43
    Microsoft states that QoS works as expected only on links where it is implemented. For remote users it can prioritize traffic only within the managed network, and Microsoft recommends avoiding real-time traffic over VPN.

    Implement Quality of Service in Microsoft Teams · Step 1 > VPN considerations · Checked 2026-09-24
44. 44
    On Windows, Teams DSCP markings are applied by OS QoS policy matching the executable ms-teams.exe and a source port range. The policy can be deployed through Intune (NetworkQoSPolicy CSP), PowerShell New-NetQosPolicy or Group Policy (Policy-based QoS).

    Implement Quality of Service (QoS) in Microsoft Teams desktop clients on Windows · Sections 'Configuring DSCP markings using Intune', 'using PowerShell commands', 'using Group Policy' · Checked 2026-09-24
45. 45
    RFC 5865 defines VOICE-ADMIT, codepoint 101100 (decimal 44), for capacity-admitted voice traffic that conforms to the EF PHB. It distinguishes this traffic from non-admitted EF traffic.

    RFC 5865: A Differentiated Services Code Point (DSCP) for Capacity-Admitted Traffic · Abstract and IANA Considerations (VOICE-ADMIT codepoint) · Checked 2026-09-24
46. 46
    RFC 5865 (May 2010) updates RFC 4542 and RFC 4594.

    RFC 5865: A Differentiated Services Code Point (DSCP) for Capacity-Admitted Traffic · Document header (Updates: 4542, 4594) · Checked 2026-09-24
47. 47
    For Webex Calling, both the Webex App and Webex devices mark audio with DSCP EF (46).

    Port Reference Information for Webex Calling · Section 'Quality of Service (QoS)/Type of Service (ToS)' · Checked 2026-09-24
48. 48
    In Webex Calling, the Webex App marks signaling CS0 (0) and Webex devices mark signaling CS3 (24).

    Port Reference Information for Webex Calling · Section 'Quality of Service (QoS)/Type of Service (ToS)' · Checked 2026-09-24
49. 49
    For Webex Calling, both the Webex App and Webex devices mark video with AF41 (34).

    Port Reference Information for Webex Calling · Section 'Quality of Service (QoS)/Type of Service (ToS)' · Checked 2026-09-24
50. 50
    RFC 8837 recommends EF (46) for WebRTC audio at medium and high priority, DF (0) at low priority and LE (1) at very-low priority.

    RFC 8837: Differentiated Services Code Point (DSCP) Packet Markings for WebRTC QoS · Section 5 (DSCP Mappings), Table 1 · Checked 2026-09-24
51. 51
    RFC 8837 requires that when multiple WebRTC flows are multiplexed over one reliable transport-layer flow, all their packets carry the same DSCP.

    RFC 8837: Differentiated Services Code Point (DSCP) Packet Markings for WebRTC QoS · Section 5 (DSCP Mappings), paragraph on TCP/SCTP multiplexing · Checked 2026-09-24
52. 52
    RFC 8837 states that the network does not trust the DSCP an endpoint sets and that the DSCP may be re-marked anywhere in the network to any value, including DF.

    RFC 8837: Differentiated Services Code Point (DSCP) Packet Markings for WebRTC QoS · Section 3 (Relation to Other Specifications), third paragraph · Checked 2026-09-24
53. 53
    RFC 8837 recommends AF41 or AF42 for high-priority interactive WebRTC video and AF42 or AF43 for medium priority.

    RFC 8837: Differentiated Services Code Point (DSCP) Packet Markings for WebRTC QoS · Section 5 (DSCP Mappings), Table 1 · Checked 2026-09-24
54. 54
    RFC 8325 maps CS5 signaling to User Priority 5 (the Video access category, AC_VI), not to the Voice access category.

    RFC 8325: Mapping Diffserv to IEEE 802.11 · Section on Signaling mapping (DSCP-to-UP mapping recommendations) · Checked 2026-09-24
55. 55
    RFC 8325 maps EF (46) to IEEE 802.11 User Priority 6, placing voice in the Voice access category (AC_VO).

    RFC 8325: Mapping Diffserv to IEEE 802.11 · Section on Telephony mapping (DSCP-to-UP mapping recommendations) · Checked 2026-09-24
56. 56
    Zoom's documented default audio marking of 56 is the CS7 codepoint, which RFC 4594 reserves and recommends dropping or re-marking at ingress. On a network that follows RFC 4594, Zoom audio left at the default is therefore likely to be re-marked or dropped rather than placed in an EF priority queue.inferred

    Using QoS DSCP Marking · Default values list; read against RFC 4594 Section 3.1 · Checked 2026-09-24
57. 57
    Zoom's own documentation disagrees on the audio DSCP. The Support KB lists 56 as the default, while the Technical Library's 4-class model table lists EF (46) among the 'common Zoom DSCP values' for audio.disputed

    Using DSCP Marking with Zoom · Using DSCP Marking with Zoom, 4-class QoS model table · Checked 2026-09-24
58. 58
    Zoom Support lists the default Zoom DSCP markings as 56 for audio, 40 for video and 40 for screen sharing.

    Using QoS DSCP Marking · Article body, default values list (heading not captured) · Checked 2026-09-24
59. 59
    Zoom states that enabling DSCP marking through the web portal or Group Policy marks only packets outbound from Zoom apps, so network devices must tag inbound traffic.

    Using DSCP Marking with Zoom · Using DSCP Marking with Zoom, section on enabling DSCP marking · Checked 2026-09-24
60. 60
    Zoom states that its outbound DSCP tags must be trusted by the computers and network components on the path to stay intact, and that tags can be stripped when traversing the Internet.

    Using DSCP Marking with Zoom · Using DSCP Marking with Zoom, trust and Internet caveats · Checked 2026-09-24

Documents

Cite this page

WarmTransfer. (2026, September 24). QoS marking and queuing for voice. WarmTransfer. https://warmtransfer.net/knowledge/qos-marking

@misc{warmtransfer-qos-marking,
  title  = {QoS marking and queuing for voice},
  author = {{WarmTransfer}},
  year   = {2026},
  url    = {https://warmtransfer.net/knowledge/qos-marking},
  note   = {Verified 2026-09-24}
}