What's the best way to emulate network jitter?

There are two ways to recreate jitter. The first way is to utilize the jitter icon. The jitter icon can provide different distributions (Gaussian, Uniform, Expontential, InterNet, Bimodal) and a time range of 100us to 10 seconds. The second way is to utilize the Accumulate & Burst impairment. This impairment creates jitter by creating gaps between bursts of packets. The user may specify the number of packets in a burst and the time between bursts. Accumulate and Burst impairment provides jitter under 1ms and the burst characteristics of the Internet.

What is the difference between routing and Ethernet bridge modes?

Routing can be used between any two IP ports. The physical ports of the emulator need to be assigned IP addresses for routing. Ethernet bridge mode works only with Ethernet ports. Ethernet bridge mode doesn't need the emulator's physical ports to be assigned addresses.

Is Ethernet the only available I/O interface?

The PacketStorm family of IP network emulators have the following interfaces available (They can be purchased separately, together or added as needed.):

10/100 Ethernet
Gigabit Ethernet
T1
E1
DS3
E3
OC3
OC12

How flexible are PacketStorm IP network emulators?

The PacketStorm family of IP emulators model each traffic flow independently; in addition, they provide the capability to impair traffic flows based upon fields set inside the IP packets.

Other emulators use a "lumped" element model. This limits not only the type of network models available but the ability to perform independent and dynamic IP network models.

For instance, the order of impairments can cause different effects to the traffic flow. If the decimate and re-order impairments are used in a network link, the impairment order will matter:

Impairment Order     Packet Flow Output
Decimate, Re-order     3,1,7,5,11,9....
Re-order, Decimate     2,4,6,8,10,12....


The PacketStorm family of IP emulators can create dynamic impairment models that change with traffic, time or the traffic behavior of another traffic flow.

An emulator should provide dynamic impairment capability to recreate "real world" conditions.The emulator should be able to reflect slow access during peak Internet usage and fast access during off-peak times. In addition, an emulator should be able to recreate any network model desired by the user.

Presently, network equipment utilizes the ToS field to ensure network QoS. In the near future, Differentiated Services (DiffServ) will become more important as voice and data converge onto the same communication network . It is therefore critical for an emulator to provide the multiple service levels of ToS and DiffServ.

What is a modifier?

A modifier allows the user to insert values into specific IP header fields. For instance, setting the TTL Decrement Modifier to 12 will make the packet appear to have gone through twelve routers.

Can the Protocol filter be used with IP address filters?

All filters can be used in any combination. For example, the user may want to create different impairments for each protocol flow between the same end points. UDP may get minimum delay while TCP would get long delays and packet loss.

Why is traffic conditioning important?

To emulate emerging IP networks utilizing Differentiated Services (DiffServ), Service Level Aggreements (SLA), and Quality of Service (Qos) in IP networks, the ability to condition and police IP network traffic is essential. Traffic Conditioning includes several Queuing methods used to condition IP network traffic (i.e., Edge routers that condition traffic based upon a SLA). Traffic conditioning is vital to emulate networks where voice, video, and data are intermixed.

What is tcl scripting?

Tcl scripting is a popular computer language to automate test applications. In fact, tcl command scripts can be embedded into larger programs to automate multiple pieces of equipment on one host computer.

What is the difference between Ethernet line rate and IP line rate?

Ethernet adds overhead bytes when encapsulating an IP packet inside an Ethernet frame.
For 64-byte packets, the Ethernet line rate is 28% greater than the IP rate.

Remember:

An IP network emulator needs to have a high throughput capability (packets/sec) and a flexible architecture to recreate real world network behavior.