DSCP & QoS Reference

A complete, searchable reference of all DSCP (Differentiated Services Code Point) values used in Quality of Service configurations. Find PHB names, binary and decimal values, IP Precedence mappings, and recommended traffic classifications for prioritizing network traffic.

DSCP	Name	Binary	Decimal	IP Prec	Traffic Class

What Is DSCP?

Differentiated Services Code Point (DSCP) is a 6-bit field in the IP header that classifies packets for Quality of Service (QoS) treatment. Routers and switches read the DSCP value to determine how to prioritize, queue, and handle each packet. This is the foundation of modern QoS — ensuring voice calls get priority over file downloads, for example.

DSCP replaced the older IP Precedence (3-bit) and ToS (Type of Service) fields, providing finer-grained traffic classification with 64 possible values. To configure QoS on your home router, follow our QoS setup guide.

Per-Hop Behavior (PHB) Classes

PHB	DSCP Values	Purpose	Queuing
EF (Expedited Forwarding)	46	Low-latency, low-jitter (VoIP)	Priority queue, policed
AF (Assured Forwarding)	10-38 (12 values)	Tiered guaranteed delivery	Weighted queuing with drop precedence
CS (Class Selector)	0,8,16,24,32,40,48,56	Backward-compatible with IP Precedence	Priority-based queuing
BE (Best Effort)	0	Default, no special treatment	Default queue

Common DSCP Markings by Application

Application	DSCP	Decimal	Priority
VoIP Media (RTP)	EF	46	Highest — absolute priority
VoIP Signaling (SIP)	CS3 / AF31	24 / 26	High — call setup
Video Conferencing	AF41	34	High — interactive video
Streaming Video	AF31	26	Medium-High — buffered
Interactive Data (web apps)	AF21	18	Medium — transactional
Bulk Data Transfer	AF11	10	Low — tolerates delay
Network Management (SNMP)	CS2	16	OAM traffic
Routing Protocols (OSPF/BGP)	CS6	48	Network control — critical
Scavenger / Background	CS1	8	Lowest — penalized traffic
Best Effort (default)	BE (0)	0	No priority

Use our VoIP Quality Calculator to see how QoS settings impact call quality. For bandwidth planning, try our Bandwidth Calculator.

Pro Tip: For home and small business networks, the most important DSCP marking is EF (46) for VoIP. Mark all voice traffic as EF and configure your router to give it strict priority queuing. This ensures clear voice calls even when someone is downloading large files. Learn how to enable QoS on your router at 192.168.1.1.

Assured Forwarding (AF) Matrix

AF provides 4 classes with 3 drop precedence levels each. Higher class = more important traffic. Higher drop precedence = dropped first during congestion:

	Low Drop (1)	Medium Drop (2)	High Drop (3)
Class 1 (Bulk)	AF11 (10)	AF12 (12)	AF13 (14)
Class 2 (Transactional)	AF21 (18)	AF22 (20)	AF23 (22)
Class 3 (Multimedia)	AF31 (26)	AF32 (28)	AF33 (30)
Class 4 (Conferencing)	AF41 (34)	AF42 (36)	AF43 (38)

Note: DSCP markings are only effective when all devices in the path honor them. ISPs typically reset DSCP values at their edge — your markings only matter within your own network. For end-to-end QoS, you need all network equipment configured consistently. For VoIP quality regardless of ISP QoS, adequate bandwidth is the fallback solution — check with our Speed Test.

Configuring DSCP on Network Equipment

# Cisco IOS — Mark VoIP traffic as EF
class-map match-any VOIP
 match protocol sip
 match protocol rtp
!
policy-map QOS-POLICY
 class VOIP
  set dscp ef
  priority percent 30
 class class-default
  fair-queue
!
interface GigabitEthernet0/0
 service-policy input QOS-POLICY

# Linux — Mark packets with iptables
iptables -t mangle -A POSTROUTING -p udp --dport 5060 -j DSCP --set-dscp 46
iptables -t mangle -A POSTROUTING -p udp --sport 10000:20000 -j DSCP --set-dscp 46

For home routers, QoS is configured through the web interface at 192.168.1.1. Most consumer routers use simplified QoS categories rather than raw DSCP values. See our QoS setup guide for router-specific instructions.

QoS Design Recommendations

Classify at the edge — Mark traffic as close to the source as possible (access switch or endpoint).
Limit priority queue to 30% — EF traffic should never exceed 30% of link capacity to prevent starvation.
Use 4-8 queues — Most networks only need: EF (voice), AF4x (video), AF2x (transactional), BE (default), CS1 (scavenger).
Trust boundaries — Only trust DSCP markings from managed endpoints; re-mark untrusted traffic.
Monitor and adjust — Use network traffic monitoring to verify QoS is working as expected.
Test after changes — Run our Network Latency Test and VoIP Calculator to confirm improvement.

Key Takeaways

DSCP is a 6-bit field in the IP header with 64 possible values for QoS classification.
EF (46) is the most critical marking — used for VoIP and real-time voice traffic.
AF provides 4 classes with 3 drop levels, giving 12 graduated service levels.
DSCP markings only matter within your own network — ISPs typically reset them.
Limit priority queue (EF) to 30% of link capacity to prevent other traffic starvation.
Configure QoS on your router with our QoS guide and verify with the VoIP Calculator.

Video: QoS and DSCP Explained

Related Tools & Guides

Frequently Asked Questions

What DSCP value should I use for VoIP?

Use DSCP EF (46) for VoIP media (RTP audio) and CS3 (24) or AF31 (26) for VoIP signaling (SIP). EF gets strict priority queuing, ensuring voice packets are never delayed by other traffic.

Does my ISP honor DSCP markings?

Most ISPs reset DSCP values to 0 (Best Effort) at their edge. DSCP is primarily effective within your own network. Some business-grade ISPs offer end-to-end QoS with SLAs that honor specific DSCP markings.

What is the difference between DSCP and IP Precedence?

IP Precedence uses the first 3 bits of the ToS byte (8 values). DSCP uses 6 bits (64 values), providing much finer classification. DSCP is backward-compatible with IP Precedence — each CS value maps directly to an IP Precedence level.

How many QoS queues should I configure?

Most networks work well with 4-8 queues: strict priority for VoIP (EF), guaranteed minimum for video (AF41), weighted fair queue for business apps (AF21), and default queue for everything else (BE). Adding a scavenger class (CS1) for backup traffic is also recommended.

Can I set DSCP values on Windows or macOS?

Windows supports DSCP through Group Policy (Policy-based QoS) for specific applications. macOS has limited DSCP support. For best results, configure QoS on your router where all traffic passes through. See our QoS guide.

What happens if I don't configure QoS?

Without QoS, all traffic is treated equally (Best Effort). During congestion, a large download can starve VoIP and video calls of bandwidth, causing choppy audio, frozen video, and poor user experience. QoS prevents this by guaranteeing bandwidth for priority traffic.

About Tommy N.

Tommy is the founder of RouterHax and a network engineer with 10+ years of experience in home and enterprise networking. He specializes in router configuration, WiFi optimization, and network security. When not writing guides, he's testing the latest mesh WiFi systems and helping readers troubleshoot their home networks.