Traffic Shaping: How to Manage Bandwidth Effectively

Traffic shaping is a technique for managing bandwidth that delays certain types of network packets to save and prioritize bandwidth for critical applications. This ensures your critical applications run smoothly. 

For example, video conferencing calls, like your Zoom meetings, need to be crisp and uninterrupted. So, you give them higher priority. On the flip side, large file downloads that can clog up the network might get a lower priority.

Traffic shaping isn't just about slowing things down. It's about being smart with your resources. By prioritizing certain types of data, you ensure your network supports your day-to-day operations effectively. 

Whether it's VoIP calls, cloud-based apps, or internal communications, traffic shaping ensures everything runs seamlessly.

Difference between traffic shaping and traffic policing

Both traffic shaping and traffic policing limit the output rate but achieve this in distinct ways. Let’s discuss their differences with some examples.

Traffic policing monitors the rate of traffic and enforces a maximum rate by dropping (or remarking) packets exceeding this set rate. This method results in an output rate that looks like a saw-tooth pattern with highs and lows. 

For instance, if a network is set to a maximum rate of 100 Mbps and the traffic spikes to 120 Mbps, the excess 20 Mbps will be dropped, immediately reducing the rate back to 100 Mbps or less.

In contrast, traffic shaping temporarily holds excess packets in a queue, then releases them in increments over time, smoothing out the rate. Think of it like a waiting room where packets queue up and are sent out in a more controlled manner. 

So, if your 120 Mbps traffic spike happens in a network with traffic shaping, the excess packets are queued and sent out gradually, maintaining a steady rate, say 100 Mbps, over a longer period.

Imagine shaping as using a buffer to smooth traffic, while policing is more like a strict gatekeeper that allows or disallows packets without delay. Shaping needs enough memory to store the delayed packets, while policing doesn't involve queues. 

For example, if a network is set with a committed information rate (CIR) of 10 Mbps, shaping will use the buffer to manage traffic bursts smoothly, whereas policing will simply drop packets that exceed the 10 Mbps limit.

Shaping is applied to outbound traffic. On the other hand, policing can be used on both inbound and outbound traffic. When shaping, tokens are replenished at the start of defined intervals, typically measured in bits per second (bps). For example, if you configure a CIR of 50 Mbps, shaping increments the token bucket in bps, smoothing the output. 

Policing refreshes tokens continuously based on the rate formula: (1 / committed information rate). With a policing rate set to 20 Mbps, tokens add up continuously, allowing for immediate decisions on packet handling.

Shaping tends to smooth the output rate and control bursts over multiple intervals using a leaky bucket to delay traffic. Conversely, policing propagates bursts without smoothing, relying on immediate packet dropping or remarking when limits are exceeded. 

Thus, shaping can delay packets by queuing them, potentially introducing latency, while policing avoids delays by dropping excess packets outright.

In a practical scenario, if an organization deals with traffic bursts from video streaming, shaping can help by buffering these bursts and releasing them steadily, ensuring smoother performance. With policing, spikes might be dropped, leading to potential disruptions in video quality due to lost packets.

Understanding these key differences helps in choosing the right method for managing network traffic based on specific needs and scenarios.

Traffic shaping vs bandwidth throttling

Bandwidth throttling and traffic shaping are both tools used to manage and control data flow but, again, they do it in different ways. To understand how they differ, imagine you're on a crowded highway. 

Traffic shaping is like setting up stoplights to manage the flow, making sure nobody is stuck too long. On the other hand, bandwidth throttling is like reducing the speed limit to ensure smoother traffic.

We use traffic shaping to optimize or guarantee network performance, reduce latency, and make the best use of bandwidth. For instance, if a link gets congested, latency shoots up. Traffic shaping can prevent this by controlling the rate at which data packets are sent, ensuring the network stays smooth and responsive.

One common type of traffic shaping is application-based traffic shaping, where you identify specific applications and apply shaping policies to them. An example is throttling peer-to-peer file sharing traffic. Some ISPs do this to limit BitTorrent traffic, which can hog bandwidth.

Encryption plays a big part here. Many application protocols use encryption to dodge traffic shaping. It makes it harder for network managers to see what kind of data is flowing, complicating the shaping process.

There’s also route-based traffic shaping. This method controls the data flow based on information about previous or next network hops. It looks at where the data is coming from or going to and shapes it accordingly.

Traffic shaping is critical at network edges – the points where data enters or exits the network. But it doesn’t stop there. Devices like computers or network cards can apply traffic shaping too. They control the amount of data being sent out, ensuring it doesn't overwhelm the network.

Shaping also isn’t just for ISPs. Data centers use it too. They manage traffic to uphold service level agreements (SLAs) for a variety of hosted applications and tenants. It ensures everyone gets fair access to the network, maintaining performance across the board.

Nodes in an IP network can unintentionally create a traffic shaping effect. This happens when they buffer packets before sending them out on a busy link. Think of it as a temporary holding area to ensure the data doesn’t flood the network.

Traffic shaping use cases and applications

Quality of Service (QoS)

Traffic shaping is a QoS (Quality of Service) technique. You can use it to enforce lower bitrates than what the physical interface can handle. 

Most ISPs use either shaping or policing to enforce "traffic contracts" with their customers. When you use shaping, you buffer the traffic to a certain bitrate. Policing, on the other hand, drops the traffic when it exceeds a certain bitrate. 

Imagine you have a fiber connection from your ISP with a guaranteed bandwidth of 10 Mbit, but the fiber interface can send 100 Mbit per second. Most ISPs will configure policing to drop all traffic over 10 Mbit. This way, you can't use more bandwidth than what you pay for. 

It's also possible they shape it down to 10 Mbit, but that means they buffer data. Policing just throws it away. The 10 Mbit you pay for is called the CIR (Committed Information Rate).

Why use shaping? 

There are two main reasons. First, instead of waiting for the ISP's policer to drop your traffic, you might shape your outgoing traffic to prevent them from dropping it. 

Second, shaping can help prevent egress blocking. This happens when you go from a high-speed interface to a low-speed one. Without shaping, you might get packet loss in your outgoing queue. Shaping ensures everything will eventually get sent.

Routers send bits at the physical clock rate. You can't change how fast electrical or optical signals travel through the cable. To get a lower bitrate, you send some packets, pause, send some more, then pause again. 

Traffic prioritization

Traffic shaping ensures that some data packets get priority over others, optimizing overall performance. For instance, if video conferencing is crucial for you, you can prioritize those packets, making the video smooth and reducing lag.

Shaping helps manage network congestion. When a network link is about to get overloaded, you can delay some data packets to keep things running smoothly. This keeps the network latency low, which means less delay in data transmission. Essentially, it makes your internet feel faster and more responsive.

You can apply traffic shaping in different ways. One common method is application-based shaping. Here, you identify specific applications, like streaming services or file-sharing apps, and control their data flow. 

For example, if people are using BitTorrent a lot and clogging the network, you can throttle its bandwidth. This technique ensures that essential business applications get higher priority and sufficient bandwidth.

Another method is route-based shaping. This approach looks at where data is coming from or heading to. For instance, if your data center traffic needs to move quickly to remote offices, you can prioritize those routes to ensure reliable and fast access.

Traffic shaping is also useful in enterprise environments. In scenarios where multiple remote offices connect to a central headquarters, shaping ensures that critical business applications have prioritized bandwidth. This avoids the need for purchasing extra bandwidth. For example, an enterprise might prioritize traffic for ERP systems over less critical applications.

Even though shaping helps in managing traffic, all shapers have a limit. When the buffer is full, excess data might get dropped. The simplest approach is known as tail drop, where packets are just dropped when there's no more room. More advanced systems might use techniques like random early detection to manage drops more effectively.

So, implementing traffic shaping means you maintain service levels without unnecessary bandwidth expenses. It balances the network load, enhances performance, and ensures key applications run smoothly.

Peak and off-peak traffic management

When managing network traffic, handling peak and off-peak times efficiently is crucial. During peak hours, everyone’s using the network simultaneously. This includes the morning rush when everyone logs in to check emails, attend virtual meetings, and sync their projects. 

You need to ensure critical applications like your VoIP phones and video conferencing tools get priority. So, you employ traffic shaping. Traffic shaping helps you assign bandwidth where it's needed most, ensuring important tasks aren't slowed down by less urgent activities.

Off-peak hours, on the other hand, are when fewer people are online. This might be late evenings, early mornings, or weekends. During these times, you have more flexibility. 

You can allow more bandwidth for non-critical activities without affecting essential services. For instance, you could schedule large backups or software updates to occur overnight. 

That way, they don't interfere with the day-to-day operations. Traffic shaping during off-peak times ensures these tasks get done efficiently without hogging resources when they're most needed.

By balancing your network load through traffic shaping, you ensure everyone gets a smooth and seamless experience, regardless of how many people are online or what tasks they're working on.