Network Instability with Office PCs 1

[nigeria]

hello I m mangaing a IP Network for a Company in Nigeria ,For last 1 weeks ,my IP Network is not Stable.There is a huge packet loss in the Network ,I concluded that there are some Computers connected to my Main Cisco Switch and when those Office Computers are Off ,there is no problem but when in the Office Time,the PCs are ON,I get major packet loss ,not all the times but it happens 8-10 times a day coz of which the entire network goes up and down.Is it a Virus or any application Problem on the PCs.Since as soon as I Isolate the Pcs Network ,the Packet Loss disappears.and If I connect the Cable after sometime the Same thing High Packet Loss is seen.Since the root cause of the Problem is not known.I m trying all the possible options.Pls give me any Suggetsion ?????

 

[Nortelshop]

Can you measure your packet loss? If so, then check you application receiver as it is the most vital in determining delay and loss. Poorly implemented end points can easily undo good QOS. I'm just a newbie, so don't take my word as the gospel.

Here is some other info. on the subject:

Simulating a Voice Call
A benefit of using SAA as the testing mechanism is it?s ability to simulate a voice call. For example, to
simulate a G.711 voice call with Real Time Protocol/User Datagram Protocol (RTP/UDP) ports 14384 and
Cisco - Measuring Delay, Jitter, and Packet Loss with Cisco IOS SAA and RTTMONabove, approximately 64 kbs per second, and a packet size of 200 bytes {(160 bytes of payload + 40 bytes for
IP/UDP/RTP (uncompressed)}, set up the SAA delay and jitter probe as described below.
For the jitter operation:
Send the request to RTP/UDP port number 14384. ·
Send 492 byte packets (480 payload + 12 byte RTP header size) + 28 bytes (IP + UDP). ·
Send 1000 packets for each frequency cycle. ·
Send every packet 20 milliseconds apart for a duration of 20 seconds. Sleep 40 seconds before
starting the next frequency cycle.
·
These parameters equal 64 kbs per second for 20 seconds ((1000 datagrams * 480 bytes per datagram)/ 60
seconds)) * 8 bits per byte = 64 kbs per second
The configuration on the router appears as follows:
rtr 1
type jitter dest-ipaddr 172.18.179.10 dest-port 14384 num-packets 1000
request-data-size 492
frequency 60
rtr schedule 1 life 2147483647 start-time now
Note: IP + UDP is not considered in the request-data-size since the router automatically adds them to the
size internally.

Proactive Monitoring of Thresholds
There are several ways to monitor the delay, jitter, and packet loss levels in the network once baseline values
have been established through the initial data collection. One way is to use the SAA threshold command.
Another is to use a feature in the Cisco IOS mainline code called RMON Alarm and Event.SAA threshold Command
The SAA feature set threshold command sets the rising threshold (hysteresis) that generates a reaction event
and stores history information for the operation. The following SAA threshold configuration on the delay and
jitter probe enables the monitoring of jitter and creates an SNMP trap upon the violation of a 5 ms threshold.
saarouter1#
rtr 100
rtr reaction-configuration 100 threshold-falling 5 threshold-type immediate