In our hyper-connected world, prioritizing specific types of data traffic has become essential. Quality of Service (QoS) is a mechanism that enables us to efficiently manage data traffic by classifying and prioritizing different types of network traffic. In this post, we dive into the application marking recommendations for QoS and understand the importance of implementing QoS for Voice and Video applications.
Decoding QoS Application Marking
QoS application marking plays a crucial role in traffic classification. Different types of traffic, such as IP routing, voice, video, and data, have distinct requirements for speed, latency, and reliability. These requirements are met through specific classification values at Layer 2 (CoS, MPLS EXP) and Layer 3 (IPP PHB DSCP). Let’s look at the recommended marking for different types of traffic:
| Application | IPP | PHB | DSCP | CoS | MPLS EXP |
|---|---|---|---|---|---|
| IP Routing | 6 | CS6 | 48 | 6 | 6 |
| Voice | 5 | EF | 46 | 5 | 5 |
| Interactive Video | 4 | AF41 | 34 | 4 | 4 |
| Streaming Video | 4 | CS4 | 32 | 4 | 4 |
| Mission Critical | 3 | Cs3 | 24 | 3 | 3 |
| Call Signals | 3 | AF31/CS3 | 26/24 | 3 | 3 |
| Transactional Data | 2 | AF21 | 18 | 2 | 2 |
| Network Management | 2 | CS2 | 16 | 2 | 2 |
| Bulk Data | 1 | AF11 | 10 | 1 | 1 |
| Scavenger | 1 | CS1 | 8 | 1 | 1 |
| Best Effort | 0 | BE | 0 | 0 | 0 |
Quality of Service for Voice Applications
Voice traffic is highly sensitive to performance indicators such as packet loss, latency, and jitter. Here’s how to handle Voice QoS:
- Voice traffic should be marked to
DSCP EFas per the QoS Baseline and RFC 3246. - Target performance standards include no more than 1% loss, one-way latency (mouth-to-ear) no more than 150 ms, and average one-way jitter less than 30 ms.
- A guaranteed priority bandwidth between 21-320 kbps per call is required, depending on factors like the sampling rate, VoIP codec, and Layer 2 media overhead.
- All three QoS quality factors: loss, latency, and jitter, directly affect voice quality and hence must be controlled judiciously.
Quality of Service for Video Applications
The QoS requirements for video traffic diverge based on whether the traffic is interactive or streaming.
Interactive Video
Interactive video, such as IP video conferencing, requires specific QoS measures:
- Interactive video traffic should be marked to
DSCP AF41. Excess traffic can be marked down by a policer toAF42orAF43. - As with voice traffic, target performance metrics include no more than 1% loss, one-way latency no more than 150 ms, and jitter not exceeding 30 ms.
- It’s recommended to overprovision interactive video queues by 20% to accommodate bursts.
Streaming Video
For streaming video, traffic should be marked to DSCP CS4. More specific recommendations vary based on individual network characteristics and will be the subject of future discussions.
In conclusion, implementing Quality of Service is vital for efficient data traffic management, particularly for voice and video applications, which are highly sensitive to latency, jitter, and loss. The above recommendations provide a starting point for determining how to classify and mark different types of traffic on your network.