Thursday, August 28, 2008

MIMIC 9.00 Performance Report: Windows vs. Linux on dual-core Pentium

MIMIC 9.00 Performance Report: Windows vs. Linux on dual-core Pentium

MIMIC is SNMP simulation software that supports up to 20,000 agents on one workstation. The main concern is the performance for a fully loaded workstation. You want at least hundreds of PDUs per second to make a simulation viable. Each hardware platform / operating system combination has different performance characteristics.

For MIMIC, performance is primarily governed by the amount of physical memory (RAM). The memory requirements depend on the simulations you are going to run. Obviously, a high-end router simulation with hundreds of interfaces, RMON tables, etc. is going to take more memory than the simulation of an end system.

As a ball-park estimate, we like to see at least 1MB of dedicated physical RAM per simulated agent, e.g., a 100 agent scenario should run fine on a 128MB system (depending on how much memory is used by the OS and other processes). For better performance (less swapping), 2MB per agent is recommended. When the agents are running the same simulation, MIMIC optimizes memory usage to contain only one copy of the simulation data for all agents of the same type.

You can more accurately measure this by running a simulation configuration, and checking on memory usage before and after starting the desired agent simulations. Notice that MIMIC uses memory on demand, so you should measure the memory after doing a walk of the desired tables (or a complete MIB walk). Eg. on Windows NT use the Windows Task Manager to check "Memory Usage", and on Unix use the "top" utility. The memory usage by MIMIC is approximately the same for all platforms.

The CPU is of secondary importance. Most modern processors (e.g., Intel Pentium 2GHz or faster, and Ultra Sparc) are adequate. MIMIC works with multi-processor systems, since it is a multi-threaded, distributed application. Agent thread processing will be distributed across multiple CPUs.

The final bottleneck would be the network pipe to your agents. 10Mb Ethernet is adequate for low-volume traffic, 100Mb is better for more demanding applications. MIMIC works with multiple network adapters on your system, so you can talk to the simulations over separate network pipes. MIMIC works with the OS-native protocol stacks, so that all network interface cards that your OS supports can be used. You can even run MIMIC over PPP.

This performance test is designed to measure peak performance of MIMIC on various supported platforms under common access scenarios. The variables in the test are the number of agents running simultaneously, and the number of agents being accessed simultaneously. It is assumed that the most common SNMP request is the GETNEXT, as is done in sequential table traversals.

This report contrasts Windows Server 2003 and XP to various flavors
of Linux on a dual-core 1.8 GHz Pentium E2160.

It shows:
1. The best performer at the low end (10 and 100 agents) is Ubuntu, by
10 to 20% better than Windows Server 2003 or XP.

2. In the mid range (1,000 agents) openSUSE is best by 10%.

3. At 2,000 agents, all OSs are comparable (within 10%), except for
Fedora 9, which lags drastically.

4. At the high-end (5,000 to 20,000 agents), the Linux contenders
(Fedora 9 and openSuSE) are slightly (upto 10%+) better than Windows
2003, which performs better when accessing the first agents, but worse
when accessing higher agents.

Wednesday, August 13, 2008

new FAQ: Why is my throughput intermittently slow on a dual NIC Linux system?

New FAQ entry for MIMIC SNMP Agent Simulator:

Q. Why is my throughput intermittently slow on a dual NIC Linux system?

A. If your Linux MIMIC system has multiple active network interfaces
connected to the same LAN, and you are experiencing drops in PDU throughput
while polling MIMIC agents in the SNMP simulation, it may be due to one network
interface running slower than the other. Linux will route traffic through
the NIC according to the arp tables regardless of the interface an agent
IP address is assigned to. The command "ethtool" run as root can be used
to discover the current speed and duplex settings of each NIC.

# ethtool eth0
Settings for eth0:
Supported ports: [ TP ]
Supported link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
Supports auto-negotiation: Yes
Advertised link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
Advertised auto-negotiation: Yes
Speed: 100Mb/s
Duplex: Full
Port: Twisted Pair
Transceiver: internal
Auto-negotiation: on
Supports Wake-on: umbg
Wake-on: g
Current message level: 0x00000001 (1)
Link detected: yes

Any protocol analyzer can be used to capture packets between the
walkhost and the agent to determine the MAC address of the NIC handling
the traffic.

Thursday, August 7, 2008

Network World: Cisco simulator can help thwart exam cheating

Gambit Communications says its MIMIC Virtual Lab software can help resolve the cheating on Cisco certification tests
By Jim Duffy , Network World , 07/30/2008

A Nashua, N.H., maker of Cisco network simulators says its software can help enterprises make sure they are hiring legitimate Cisco-certified engineers to run their networks.

Gambit Communications says its MIMIC Virtual Lab software, which has been on the market for about four years, can help resolve the recent spate of cheating on Cisco certification tests by enabling enterprises to run network operations candidates through sample scenarios before hiring them. This allows enterprises to screen candidates to ensure they are not hiring fraudulent network operators at handsome salaries.

Cisco recently moved to thwart cheating on certification tests by employing photo identification requirements and a data forensics program. According to Cisco, pilot programs using the new detection methods have already uncovered 1,400 suspected cheaters who hired proxies to take the exams for them.

But Gambit claims the photo and forensics programs only go so far: what about the many unqualified candidates already hired by enterprises prior to the new Cisco enforcement programs?

Sit 'em down and run them through a simulated lab environment, Gambit says.

Gambit's CCNA Virtual LAB software starts at $99 and can be downloaded to a laptop or PC. It creates a simulated environment with seven Cisco devices – Catalyst 2950, 3550 and 6500 switches and 2620, 3640 and 7206 series routers -- and users can type in IOS and SNMP commands to configure devices and protocols.

Test conductors and "students" can replace and establish LAN, WAN, ISDN and serial links, change IP addresses and create virtual LANs with the program, but cannot change the devices themselves. Also, the program is not certified by Cisco but is resold by a Cisco – certified training partner, Tech 2000. Cisco also uses the CCNA Virtual Lab's predecessor, the MIMIC Simulator Suite for IOS, Gambit says.

Gambit says it has 1,000 customers for CCNA Virtual Lab since it was introduced in 2002, including AT&T, IBM, the U.S. Army and several financial firms.