Application Performance Engineering Blog – Shunra Software

Shunra VE Modeler, the well known Microsoft Visio-based Shunra console, makes network modeling quick, easy and straightforward – I think most Shunra users will agree with this statement. Still, some users run into issues with VE Modeler which are easy to avoid.

I have been working with Shunra users for several years now and I wanted to share my experience to help others avoid common network modeling roadblocks and fast forward the learning curve for our new users.

1. To emulate a symmetric link (say T1) of a remote branch (say NY) you will need to set bandwidth to T1 only once (on one ‘NIC’) on the ‘Gateway Shape’ which is contacted to the NY site. For example, set bandwidth value to 1544 Kbps in ‘NIC 1’ of ‘Gateway Shape 1’ (do not set 1.544 Kbps on ‘NIC 1’ and 1.544 Kbps on ‘NIC 2’ of the same ‘Gateway Shape’ – this will double the T1 affect).
2. To emulate an asymmetric link (say downlink is T1 and uplink is 256 Kbps) on one ‘Gateway Shape’ you will have to use the ‘Uni – Directional’ links and a gateway shape with at least 3 NICs on it. For example, use a gateway shape with 3 NICs (say ‘Gateway Shape 1’) and set 1.544 Kbps on ‘NIC 2’ and 256 Kbps on ‘NIC 3’. Next step is to connect ‘Gateway Shape 1’ to the WAN (in our case the WAN will be represented by a ‘WAN Cloud’ Shape). Use one ‘Uni – Directional’ link that goes from the WAN into ‘NIC 2’ (downlink = T1) and another “Uni – Directional” link that goes from ‘NIC 3’ to the WAN (uplink = 256 Kbps).
3. Remember if you are using a Ping command to monitor network delay of a real production link – Ping provides RTT (Round Trip Time) which is the time it takes the Ping request to reach the destination host plus the time it takes the Ping reply to reach the source host. In VE Modeler you will need to set Latency per direction and therefore you will need to set the Latency to RTT / 2.
4. VE Modeler 5.30 allows setting network delay in microseconds. When attempting to emulate Fixed Latency greater than 1 ms (say 30ms) – make sure you set the value in the Cloud Shape to 30.00 millisecond and not 00.30 millisecond. The later (00.30) stands for 300 microseconds..
5. A valid emulation path cannot have more than one ‘Link’ connected to the same ‘NIC’. Paths that come and go through the same ‘NIC’ will not be impaired.

I hope this helps.

Sharon Levin