Ethernet basics

[Nas.CloudBusinessPortal]

Just a quick question on Ethernet transmission

When Ethernet goes by 2.5 gb and then by 1 gbe, to devices that could be even 100 mbps,

Is there a buffer in the ASUS router switch, to hassle the speed differences.

I get it, the importance of network setup, so that your not bottle necking and Ethernet line.

Is there a site to general I formation on Ethernet transmission?

 

[Justinh]

I'm sure there are many sites offering general info on Ethernet. "Google it", as they say.

There is no buffering. The slowest node limits data flow across the path from sender to receiver.

 

[drinkingbird]

Just a quick question on Ethernet transmission

When Ethernet goes by 2.5 gb and then by 1 gbe, to devices that could be even 100 mbps,

Is there a buffer in the ASUS router switch, to hassle the speed differences.

I get it, the importance of network setup, so that your not bottle necking and Ethernet line.

Is there a site to general I formation on Ethernet transmission?

If two devices are directly connected, they will negotiate to the lowest supported speed by the two of them.

If they are connected to a switch (or any other device with differing port speeds) with one device at 2.5 and one at 1G, then there are several buffers in the path that may get used, one on each client, one on each switch port, if a router is involved, one on each router port. Depending on the scenario, some or all of these buffers may get used (sometimes it will just be one or two of them, depending where in the path the bottleneck is). But those buffers are relatively small, it is TCP that will detect the bottleneck and throttle back once those buffers start dropping packets. However it is not a "pretty" throttling, it will keep ramping up, detecting the packet loss, throttling back, repeat over and over. For UDP, there is no throttling back, if you attempt to exceed the slowest link speed it will heavily drop packets and your stream will get very glitchy. This is why apps that use UDP often also have a TCP connection between them to request retransmissions of missed messages. But that only helps for occasional loss for the most part unless the app is designed specifically to deal with heavy drops, essentially it must delay/pre-buffer the stream enough so that it can "fill in the gaps" without you ever noticing. Note application buffering is totally different, that uses RAM on the client machine where the app is installed, not network/hardware port buffers.

There will be packet drops and retransmissions if you attempt to exceed the speed of the slower device no matter what. That is a normal part of ethernet (or really any data) communications. Even if both devices are the same speed, saturating the connection will result in buffer hits and eventually packet drops and TCP throttling back. The application layer (and most of the layers until you hit the network/data link layer) have no idea what the physical link speed is. Certain apps you can set a max speed/tell it what the link speed is and it will shape and throttle traffic to try and stay within that. Not very common on typical consumer oriented applications though.

It isn't something to be overly concerned with, it is a normal part of data communications. The buffers in the asus are likely pretty small, but larger ones wouldn't make much difference with that kind of mismatch (2.5 and 1 or even 2.5 and 100M). Too large of a buffer can also cause problems.

 

[bbunge]

AS was stated above, Google is your friend. for basics see: https://computer.howstuffworks.com/ethernet.htm

However, you will glaze quickly. What is important is to use the right hardware especially cables. For up to 1 GB use CAT5 cables at a minimum. Up to 2.5 GB use CAT5e at a minimum. Some may say to use CAT5e for 1 GB and CAT6 for up to 2.5 GB and neither is wrong. There are other considerations you can learn or look up in time.
One standard for cables determines how the wires are connected at the connector. It is recommended to use the same cable standard within a run. TIA/EIA 568a or TIA/EIA 568b.
And be kind to your cables. No kinks or sharp bends. Replace or repair damaged cables before trouble happens.

 

[drinkingbird]

AS was stated above, Google is your friend. for basics see: https://computer.howstuffworks.com/ethernet.htm

However, you will glaze quickly. What is important is to use the right hardware especially cables. For up to 1 GB use CAT5 cables at a minimum. Up to 2.5 GB use CAT5e at a minimum. Some may say to use CAT5e for 1 GB and CAT6 for up to 2.5 GB and neither is wrong. There are other considerations you can learn or look up in time.
One standard for cables determines how the wires are connected at the connector. It is recommended to use the same cable standard within a run. TIA/EIA 568a or TIA/EIA 568b.
And be kind to your cables. No kinks or sharp bends. Replace or repair damaged cables before trouble happens.

I wouldn't bother using cat5 for 1G. It is rated for 100M, sure it may be able to do 1G at shorter distances, but why risk it, and a lot of CAT5 patch cords only have 2 pairs in them and will only come up at 100M no matter what.

Stick with the spec, heck CAT5e is cheaper than CAT5 these days anyway.

Technically it is
5e up to 2.5G
6 up to 5G at 100M or 10G at varying distances (20 to 50 meters depending on environment)
6e will do up to 10G at 100M
7 is not a fully recognized standard but as long as it isn't a fake/crap cable will do 10G at 100M and 25/40G in certain circumstances
8 will do the same, not necessary, true 6e is plenty. 8 is more for 25/40/50G but that's going to be very uncommon. At that point, you should be using fiber.

But none of that really relates to buffers or how two different speeds interoperate with each other.

 

[sfx2000]

There is no buffering. The slowest node limits data flow across the path from sender to receiver.

Yep, and only on that path - source to sink...

 

[drinkingbird]

I'm sure there are many sites offering general info on Ethernet. "Google it", as they say.

There is no buffering. The slowest node limits data flow across the path from sender to receiver.

There is buffering, even when both endpoints are the same speed.

There is no communication between devices to tell each other their maximum transfer speed. Unless they are directly connected, they have no way of knowing the other has a different link speed.

Every single network port in the path has buffers on it, as well as (almost always) flow control to try and slow down the communications and prevent buffer overflows when things are at line rate.

Buffers are critical to proper function of ethernet.

 

[drinkingbird]

Yep, and only on that path - source to sink...

Huh?