UDP drop rate in home lab

[aregaard]

Hi,

I have three different networks in my home lab (daisy chain topology). They are seperated with two Cisco Routers (LEFT:192.168.1.0/24, MIDDEL:192.168.2.0/24, RIGHT:192.168.3.0/24.The load is close to zero on all networks. Fast Ethernet is used.

1. what is a normal drop rate of UDP datagram  (<1470Bytes) sent with very low data rate.

2. what can effect the drop rate except for buffer memories? E.g high data rate.

I get somewhere around 0,005% drop of my udp-package . Is this normal? For me it sounds pretty high due to the low load on the network and the data rate is super low.

[Joseph W. Doherty]

"1. what is a normal drop rate of UDP datagram (<1470Bytes) sent with very low data rate."

There's really no "normal" drop rate.  Drop rate depends on how a flow is being transmitted, "nature" of the packets, configuration of the router and particular router being used.  BTW, often when someone mentions "low data rate" they are referring to some longer term (often 5 minute) usage average, but drops occur at the millisecond level.

"2. what can effect the drop rate except for buffer memories? E.g high data rate."

Most of the other things that can affect drop rate noted in prior question's responses.  BTW, unless your "high" exceeds 100%, often interface can transmit at 100% w/o drops.

[aregaard]

The more I read my question the more I understand that it is very hard to help me.

So a transmission during serveral hours with a “Hello World”-string every third second should not generate a drop? I am aware that the drops depends on many parameters. That’s why I wrote low data rate—> no load on the networks, to try to provide some background. But maybe that does not provide any extra help to calculate a generic loss?
but are there any lead values to compare to? Like a procent of generic loss?

so How can I estimate if the drop is OK and according to generic values or if there is something faulty in my setup?

I tested several different setups with the router. Static routing to dynamic routing. With Encryption,  no encryption.

I just try to measure what UDP-drop is to expect on smaller CANs.

[Joseph W. Doherty]

Unfortunately, there's not any one size fits all, when it comes to drops, especially for UDP traffic.  With TCP, there's a rough rule of thumb that up to about 1% loss can be tolerated.

The primary cause of drops is overflowing a queue.  Generally this happen when there's a "burst" of traffic, usually cased by a "faster" ingress interface exiting a "slower" egress interface, or multiple ingress interfaces, whose aggregate traffic exceeds the "speed" of a shared egress interface.

On Cisco's software based routers, sometimes the CPU can be overloaded such that it's unable to keep up with its traffic, especially if packets need to be "processed" forwarded.

All that said, if all you traffic is a "hello world" every three seconds, that indeed is "low" and generally would expect any drops.

What model(s) are your routers and the IOS version(s) running on them?

[Georg Pauwen]

Hello,

this is a continuation of an older post. What exactly is your current problem ?