LAN Speed Degradation

[dmimagecam1]

Hi Everyone,

This is a rather quick question in regards to what impact equipment with varying LAN connection speeds affects the entire network as a whole.

Over the past year I have been systematically swapping out old 10/100 switches for their GB counterparts this goes for the smaller 5 ports that run on the shop floor as well as well as eliminating 16/24 port switches for 48 port switches. My question is with establishing a GB network ( as far as switching and cabling goes ) what affect does equipment that runs at Base10x, like CNC machines have on the network?

Is the network only capable to run at the slowest device on the network? I've always wondered this. Our shop floor contains many pieces of equipment that access the network to retrieve files but these machines only are capable of 10Base-T where as our office computers are all capable of 1000Base-T but all reside on one LAN that is not segregated.

What would the impact on overall network speeds be with the varying equipment and their respective connection speeds.

Thanks

[chrihussey]

If I understand your question correctly, network speeds will vary based on devices involved in the data exchange. However, in a network with a combination of 10/100/1000 NICs, an exchange between two gigabit devices is not slowed down due to the fact that there are also 10mbs (slower) devices running in the same environment. 

However, if a gigabit device is communicating with a 10mbps device, it will of course have to perform to the capability of the slower device.

Hope this helps

[Joseph W. Doherty]

. . . an exchange between two gigabit devices is not slowed down due to the fact that there are also 10mbs (slower) devices running in the same environment.

That's not always true.  Much also depends on the architecture of the switch.  For example, switch might have a head-of-line blocking issue (much, much less common then it was years ago).  Or, for example, switch might use buffers from a shared pool and a congested port could exhaust buffers needed by other ports.

You can also run into issues just because of the greater "speed" difference between ports.  For example host sending at 100 Mbps cannot physically (on network) overrun a host also receiving at 100 Mbps, also host sending at 100 Mbps can send data 10x faster than 10 Mbps can transmit, but if the sending host is now gig, it also can send to 100 Mbps host 10x than before and 100x faster to 10 Mbps than before.

Also, if two hosts are upgraded from 100 Mbps to gig, not all hosts might be able to deal with gig in a sustained transmission.

The foregoing is just a way of saying, although there might not be anything "wrong" with your new switch hardware, upgrading to gig, especially while still running hosts at less than gig, can cause some unexpected results.

[dmimagecam1]

Thank you for the replies. Lots of good information and I'm glad I was able to get my question across. I have a long way to go and still some cleanup, I am the companies first on site IT support so many years of mix matched devices so I've tried my best to number one get rid of consumer based lower end equipment and at least get in some better quality products that are more conducive to a business environment but as many know it's difficult to answer question of why is the network slow, you have to start somewhere and hopefully lead them in the right direction.

And without the ability to really see the traffic itself I rely on the expertise of members such as yourselves to fill in the gaps and doubts. I do understand its not as simple as replacing equipment and that is a guarantee but there have been improvements, in my opinion as a whole. As mentioned being new to the company and a new role completely comes with it's own challenges because your sometimes viewed as there's the guy spending all the money but there is a lot to be said for reliability and reducing that downtime %.

Really appreciate you all taking the time to answer my question.