Tag Archives: network packet broker

Use monitoring resources more effectively thanks to intelligent Load Balancing


Often, analysis, monitoring and security systems have more than one port to accept and process incoming data from the corresponding network access points. Many of these systems have at least 2, 4 or even more ports ready to accept data.

Depending on the type and location of the various network access points, this offers the user the option of providing a dedicated physical port per tapped line. However, several factors are a prerequisite for this.

The speed and topology of the network lines to be analysed must be identical to the connections of the analysis system and it must be ruled out that further tap points are added in the future which are to be evaluated by the same analysis system.


Apart from the problems with speeds and topologies, additional analysis systems can of course be installed at any time should the number of lines to be monitored increase.
However, this is often the most costly and time-consuming alternative. Besides the necessary procurement, it would mean for the user to deal with yet another system; an avoidable additional administrative effort.

To avoid such a situation, there are various options and, depending on the setup already in place, technical procedures can be used to distribute the incoming data from the measuring points more effectively to the physical ports already in place.
In many cases, it is primarily the ratio of data volume and number of measurement points to the number of available ports on the analysis system and not the basic amount of data volume that can lead to bottlenecks of a physical nature.

Both (semi-dynamic) load balancing and dynamic load balancing can help here, a feature that most network packet brokers include.
Here, a group/number of physical ports is combined on the Network Packet Broker and defined as a single logical output instance. Data streams that leave the Network Packet Broker via this port grouping are distributed to all ports that are part of this grouping, but the individual sessions remain intact.


Dynamic Load Balancing Example Diagram

Let us assume the following example: 8 measuring points have been set distributed in the local network. A session between 2 end points runs via each tap point. The analysis system used is equipped with a total of 4 ports for data acquisition.
Even if one assumes that the measuring points are exclusively SPAN or mirror ports, there is still the problem that too many measuring points meet too few ports.

And this is where Network Packet Brokers with Load Balancing come into play. Load Balancing ensures that each session between 2 end points of each measuring point is sent as a whole to a single port of the connected analysis system.
For simplicity, assume that the 8 sessions of the 8 measuring points are distributed equally among the 4 ports of the analysis system, 2 sessions per port.

This is all completely dynamic and subsequently added sessions between endpoints are sent fully automatically to the ports of the analysis system that belong in the port grouping. It is not necessary to set up or change the configuration of the Network Packet Broker afterwards; the built-in automatisms allow the automated and reliable distribution of further data streams to the analysis system.

Of course, it is also possible to connect additional tap points to the Network Packet Broker and have their data included in the Load Balancing, as well as to expand the above-mentioned port grouping with additional output ports.
All these steps can be taken during operation, the additional data streams are distributed to the newly added ports of the analysis system in real time without interruptions.

Removing ports, even during operation, is no problem either! The Network Packet Broker is able to ensure that the packets/sessions are forwarded to the remaining ports of the analysis system without any loss of time or packets.

Dynamic Load Balancing Example Diagram without Network Packet Broker

Sessions & Tuples

But how can the Network Packet Broker ensure that entire sessions are always distributed on the individual ports of the load balancing group mentioned above?

For this purpose, a hash value is generated from each individual package. An integrated function ensures that in the case of bi-directional communication, the packets of both transport directions leave the Network Packet Broker again on the same port.

These hash values are determined using the so-called “5-tuple” mechanism, where each tuple represents a specific field in the header of each Ethernet frame. The available tuples on the Network Packet Broker (e.g. NEOXPacketLion), which are used for dynamic Load Balancing, are:

  • Input Port (Physical Connection)
  • Ethertype
  • Source MAC
  • Destination MAC
  • VLAN Label
  • MPLS Label
  • GTP Tunnel Endpoint Identifier
  • GTP Inner IP
  • IP Protocol
  • Source IP
  • Destination IP
  • Layer-4 Source PORT
  • Layer-4 Destination PORT

Depending on the structure and setup of the network, and depending on whether packets are transported using NAT, another very common distribution of tuples is:

  • IP Protocol
  • Source IP
  • Destination IP
  • Layer-4 Source PORT
  • Layer-4 Destination PORT

With “5-tuple” based Load Balancing, all the above-mentioned tuples are used to form a hash value which ensures that all packets, including the corresponding reverse direction, always leave the Network Packet Broker via the same port and thus, for example, the security system used always and fundamentally only receives complete sessions for evaluation.

Hash Values

In order to be able to generate the actual hash value on which the Load Balancing is based, the user has two different functions at his disposal, CRC32 and XOR.

By means of the CRC32 function, hash keys with a length of 32 bits can be generated and can be used both symmetrically and asymmetrically, while the XOR function creates a 16-bit long hash key, which, depending on the intended use, allows a higher-resolution distribution of the data, but can only output it symmetrically.

This symmetry means that even if the source IP and destination IP are swapped, as is known from regular Layer 3 conversations, the function still calculates the same hash key and thus the full Layer 3 conversations always leave the Network Packet Broker on the same physical port.

In the case of an asymmetric distribution, which is only supported by the CRC32 function, the Network Packet Broker PacketLion would calculate different hash values in the situation described above and thus also be output accordingly on different physical ports.

Dynamic Load Balancing - Screenshot - NEOXPacketLion Network Packet Broker
NEOXPacketLion Network Packet Broker – Screenshot

Dynamic Load Balancing

Another, additional function of Load Balancing is the possible dynamics with which this feature can be extended. In the case of dynamic Load Balancing, in addition to the hash value explained above, the percentage utilisation of each port that is part of the Load Balancing port group is also included in the calculation.

Of course, this procedure does not split any flows, and it also ensures that if a flow is issued based on the calculations on a specific port, this flow will always leave the Network Packet Broker via the same port in the future.

By means of a configurable timeout, the user can define when a flow loses its affiliation to an output port. In the event of a recurrence, this is then output to the participants of the load-balancing port group again in a regular manner and, both by detecting the load in the TX stream and by means of the hash value generation, it is determined which output port of the Network Packet Broker is currently most suitable for bringing the data to the connected analysis system.


It turns out that distributing the incoming data load by means of load balancing has been an effective way of utilising security, analysis and monitoring systems for many years. Over the years, this process has been further improved and culminates in the Dynamic Load Balancing that the PacketLion series has.

Constantly following up the configuration with regard to the distribution of the individual sessions to the connected systems is no longer necessary; this is now taken over by the intelligence of the Network Packet Broker and allows the user to use the full potential of his systems and avoid unnecessary expenditure.

Stay at the cutting edge thanks to Packet Slicing

Slicing - Photo by Brands&People


Sling - Photo by Brands&People

Often the gap between the capacity of the recording analysis system on the one hand and the amount of incoming data on the other is so large that without appropriate additional mechanisms the analysis system is most likely not able to record all individual packets without loss.

Depending on the purpose of the analysis system, this is a major problem, as every packet counts, especially in the cyber security environment, and otherwise it is not possible to ensure that all attacks and their effects are detected.

Attacks that are not detected in time or even remain completely invisible can cause enormous damage to companies, even leading to recourse claims from possible insurers if they discover that their clients did not fulfil their duty of care.

But how does such a situation arise? It can happen very quickly that networks in companies grow, often in parallel with the business development of this company, while the often already existing analysis and monitoring systems, planned with reserves during procurement, reach the end of their reserves more and more often.
Higher bandwidths, more and more services and interfaces used in the LAN reduce the capacities to the point where the systems can no longer keep up and have to discard packets.
Photo by Lars Kienle
From this moment on, it is theoretically possible for an attacker to stay undetected in the local network, as the analysis system is hopelessly overloaded. The administrator is no longer able to see which parties in his network are talking to each other, which protocols they are using and which endpoints are being communicated with outside the LAN.

Often, however, it is not capacity problems that trigger the activation of Packet Slicing, but rather data protection reasons. Depending on where and which data is tapped and when, it may be obligatory for the company to only record and evaluate data that does not contain any personal or performance-related information.

While typically the packet header only contains connection data (WHEN, WHO, HOW, WHERE), the payload data, although usually encrypted, contains the very content data that theoretically makes it possible to measure the performance of individual users. Depending on the place of use, however, this is often neither wanted nor allowed. It must therefore be ensured that it is not possible for the administrator to reconstruct personal information from the recorded data.

Reduce analysis data by means of Packet Slicing

87 percent less thanks to Packet Slicing
And this is exactly where the “Packet Slicing” feature comes into play: with this procedure it is possible to reduce the incoming data load on your analysis system by up to 87% (with 1518 bytes packet size and Packet Slicing at 192 bytes) by simply removing the user data from each packet.

Many analysis and monitoring approaches only need the information stored in the packet header, i.e. the metadata, for their evaluations and analyses, while the user data often does not contain any important or usable information, as this is usually encrypted anyway and thus cannot be used for the evaluation.
By removing the user data, a massive relief of the processing instance is to be expected, and in some cases this enables even greater coverage of the LAN by the monitoring and analysis device.

FCS Checksum Problem

An important aspect of Packet Slicing is the recovery of the FCS checksum of each modified packet. Since the structure and length of the packet is affected by cutting away the user data, the originally calculated checksum, which was calculated by the sender and entered in the FCS field of the packet header, is no longer correct.

As soon as such a packet arrives on the analysis system, those packets are discarded or declared erroneous, as the checksum in the FCS field is still based on the original packet length. To counteract this, it is essential that the FCS checksum is recalculated and also entered for each packet from which the user data has been removed, as this would otherwise force the analysis systems to classify these packets as faulty and/or manipulated.

Network Packet Broker as a Packet Slicer

In general, there are several possibilities where the above-mentioned Packet Slicing can be activated in the visibility platform used by the customer. On the one hand, this is a case-by-case decision, on the other hand, it is also a technical one.

NEOXPacketLion - Network Packet Broker - Network Monitoring Switch | Data Monitoring Switch

Assuming that the user has set several measuring points distributed in his network, a Network Packet Brokeris often used. This device is another level of aggregation and is typically used as the last instance directly before the monitoring system. A Network Packet Broker is optically very close to a switch and enables the user to centrally combine the data from multiple measuring points (Network TAPs or SPAN ports) and send them aggregated in one or more data streams to the central analysis system.

Thus, for example, the data from 10 distributed measuring points set in 1 Gigabit lines can be sent to an analysis system with a single 10 Gigabit port by the Network Packet Broker aggregating these 1 Gigabit signals and outputting them again as a single 10 Gigabit signal.

NEOXPacketRaven Network TAP - OM4 to RJ45At this point, however, the user learns of a catch to the whole issue: often the analysis systems, although equipped with a 10Gigabit connection, are not able to process bandwidths of 10Gigabit/second as well.

This can have a variety of reasons, which, however, should not be the subject of this blog entry. However, the initial situation is predestined for the use of Packet Slicing; while one would normally have to expand one’s monitoring infrastructure at immense cost, by switching on Packet Slicing one can massively reduce the incoming flood of data and thus continue to use one’s existing systems; all that is needed is a corresponding instance with precisely this feature, which usually costs only a fraction of what would be estimated for an upgrade of the analysis systems.

Analysis Systems as Packet Slicers

Napatech High Performance Smart-NICsAnother possibility is offered to the user on the analysis systems themselves. Depending on the manufacturer, structure and components used, it is possible to directly remove the user data on the systems themselves and recalculate the checksum before the packets are passed on internally to the corresponding analysis modules.

In the vast majority of cases, an FPGA-based network card is required for this, as it must be ensured that no CPU-based resource is used to modify each individual packet. Only by means of pure hardware capacities can the user be sure that every packet is really processed accordingly; any other approach could again lead to the errors and problems mentioned at the beginning.

Packet Slicing to meet Legal Requirements

Another aspect worth mentioning is the fulfilment of legal requirements. Especially in the context of the GDPR, it may be necessary to remove the user data, as often the metadata is sufficient for an analysis.

For example, if you want to analyse VoIP, you can use Packet Slicing to ensure that unauthorised persons cannot listen to the conversation, but you can still technically evaluate the voice transmission and examine it for quality-of-service features. This allows performance values to be evaluated, privacy to be protected and legal requirements such as the GDPR to be met.


So we see that there are indeed different ways to distribute the final load on the analysis and monitoring systems or even, as in this example, to reduce it without losing the most important information for creating performance charts, top talkers and more. Packet Slicing is therefore a valid solution for the user, which can be easily implemented in almost all cases and achieves usable results.

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