Preseem ISP Radio Interview: Packet Buffering, Network Latency, QoE, and More!
Dan Siemon and Scot Loach from Preseem appeared live on ISP Radio with hosts Steven Grabiel and Dennis Burgess on April 4th, 2018. The main topic was the concept of packet buffering and its impact on an internet subscriber’s quality of experience (QoE).
The one-hour long session also covered other topics of interest for network managers and WISP operators, such as:
- Understanding packet buffering and its effect on network latency
- Why do network elements have queues?
- Impacts of queuing packets
- Better ways to manage queues through AQM and FQ-CoDel
- How Netflix actually behaves on a network (hint: it’s not a stream)
Many WISPs joined and asked questions during the live show. It was also recorded for everyone’s benefit and here it is!
Key Takeaways
1. Most WISPs and network operators believe that packet networks have high latency upon loading. Also, this poor performance is so prevalent that many think it’s just the reality of the internet. In reality, high latency under load is the result of poor packet buffering.
2. Managing packet buffering is like the “Goldilocks problem.” If you have too little buffer, you have poor link utilization. If you have a lot of buffer, there’s a lot of latency and the interactivity of the network suffers. Active Queue Management (AQM) helps WISPs solve big buffer problems by automating what packets to drop and when.
3. Advancements in algorithms like FQ-CoDel ensure that interactive applications like VoIP or gaming are not negatively impacted by high-bandwidth applications like Netflix or device updates. Example: a subscriber complained that his game sessions were “laggy” while his wife was watching Netflix. With Preseem’s plan enforcement, based on FQ-CoDel, the subscriber’s game latency stayed low while his wife’s video quality didn’t change.
4. Most ISPs enforce plan rates on some element in the network, such as access point/SM, intermediate router/switch, etc. Typically, these don’t have enough buffering or use a simple, deep tail-drop queue resulting in poor QoE under load. These problems are taken care of by QoE-optimized plan enforcement based on FQ-CoDel.
5. Netflix is by far the most popular application on the internet. About a third of traffic on a typical ISP network is Netflix. Most WISPs consider Netflix as a stream like other applications. In reality, however, Netflix actually downloads chunks of content to a buffer and uses multiple TCP connections. Netflix videos are also variable bitrate encoded, making it impossible to limit resolution with network policy. Netflix also downloads in short bursts at full link rate, which can negatively impact other traffic. Subscriber/flow isolation (e.g. FQ-CoDel) can solve this problem.
Q&A
Here’s a snapshot of some of the questions asked by listeners during and after the broadcast:
Q: If you have a lot of bandwidth, can that also take care of buffering and network latency issues without the need for FQ-CoDel?
Dan: If someone has infinite backhaul bandwidth, they won’t need FQ-CoDel but very rarely does that happen for a typical WISP. Bandwidth is precious for almost all network owners and managers. Going beyond an individual customer’s traffic management, FQ-CoDel helps fix network congestion at any part of a network. Whenever there’s congestion, there’s a queue and applications based on FQ-CoDel will help manage that problem.
Q: Where is the FQ-CoDel implementation on a typical WISP network?
Dan: Abstractly, it can be at any place where there’s a queue in the network. In the case of Preseem, which uses FQ-CoDel to optimize QoE in a WISP network, it’s deployed at the highest point where there’s no asymmetry in a network. If a WISP has one individual transit link, we’re deployed in front of that. If there are multiple transit links, different boxes can be deployed running Preseem software. All data is then collected and analyzed in the cloud with a collective presentation for the operators. For Preseem to apply fair shaping and per-flow prioritization, it needs to own how plans are enforced and no other tool down in the network should affect the subscriber plans.
Q: Does Preseem function as the billing system’s radius client that actually controls the bandwidth for each individual subscriber?
Dan: Preseem has API integrations with billing vendors like Sonar, Powercode, Azotel, VISP.net, BillMax, and also other custom integrations as well. Preseem just needs to be told which IP address belongs to which subscriber, and also their plan speeds, and it does the rest. It seamlessly integrates with billing systems used by WISPs. When the integration is turned on, Preseem gathers all the information on plan speeds and subscriber information, and it just works.
Q: Can Preseem peer into unincorporated PPoE packets to do bandwidth control?
Dan: Yes, we have WISPs doing this. It’s just a configuration to say the subscriber traffic is inside PPoE or VLAN and it hops over the headers and gets it done.
Q: Any stories from the WISP community where they used Preseem and saw dramatic improvements?
Dan: We have a lot of reviews listed on our website. The most common feedback is when WISPs say that complaints of people with internet feeling slow during downloads or Netflix streaming have just gone away since Preseem was deployed.
Q: Do you support bandwidth-limiting customers with multiple IPs? For example, a customer has a 10 Mb plan with multiple IPs?
Dan: Any IP is bound to a subscriber and if they go through the same box, they’d be grouped together under that subscriber’s traffic envelope. If you have two IPs with a subscriber at 10 Mb, then the two of them will be shaped at 10 Mb together. To avoid this, use a plan identifier along with the subscriber identifier to allow for separate 10 Mbs for each IP.
Note: this is an edited version of ISP Radio’s show. For the full version, please visit this link.
Preseem’s QoE optimization provides per-flow fairness and prioritization. This allows interactive flows like VoIP, gaming and DNS to get through smoothly without being affected by bulk flows like streaming video and large Windows downloads. This also ensures that your customers don’t call to complain about slow Internet while someone else in the house is online. Contact us for a free 30-day trial.
