Questions about Ethernet ports.

[ipwn3r456]

Hello everyone,

I know there are routers, modems, switches, etc. that are rated 10/100 mbps, 1gbits, or 10gbits. But does that mean 100mbps total bandwidth from download and upload? Let's say, if I have a 100/100 mbps connection (100mbps download and upload), if I connect it to a 100mbps port, and downloading and uploading at around 90mbits, would it get bottlenecked because of the 100mbps port?

 

[bill001g]

wired ports are rated for simultaneous up and down transfer. So if you were to use the lies wireless tells you would call a 100m port a 200m port and a 1g port a 2g port.

There are bottlenecks when you get very close to the rated speed. If you are only using a single machine it does not happen but if you say would have 2 machine each running on 100m ports and then send those packets to a third machines port. If they decided to send data at the same exact instant the switch needs to buffer the data. If you are sending data very close to the capacity of the port you can overload this buffer for very short periods of time and take packet loss. 85-90% is generally where you start seeing the problem. It really depends on all kinds of factors like packet size and number of sessions how close to 100% utilization you can actually get. Anything under 70% you seldom see any loss at all. And these utilization number are independent for up and down.

 

[RaDiKaL_]

90mbits < 100mbps so there wouldn't be a bottleneck, because 100mbps ports and higher when working at full-duplex (default mode unless your ethernet cable is not built right or having a 10mbps device in the network) will grant you 100mbps download and 100mbps upload simultaneously.

 

[DeauteratedDog]

For a 100 Mbps port, as long as the port is Full-Duplex, then you have 100 Mbps in both directions simultaneously - 200 Mbps aggregate. If it is Half-Duplex, then you still have 100 Mbps, but either 'up' or 'down' at any given instant.

 

[ipwn3r456]

Thanks for the answers so far. But how do you know if it's working on full-duplex, or how do you determine if the Ethernet ports or cables are full-duplex?

 

[bill001g]

It is extremely rare to find equipment that can not run full duplex. This is remnant from the old days when they sold old 10m HUBS.

Pretty much the only way it happens now days is you mess with the settings and don't leave the setting on auto.

with unmanged stuff you can only hope the lights will indicate. I guess the best way to to try to always run at gig there is not such thing as gig/half

 

[DeauteratedDog]

It depends on the device. Nicer switches will turn a LED on or change it's color to indicate speed and duplex.

For my (Intel) Ethernet adapter under Windows 7: right mouse on the adapter, select properties, select configure, select link speed tab.

Most operating systems or devices like switches and routers have some way to find the port status.

 

[ipwn3r456]

I hope my router is full duplex. I am just asking this because I might upgrade to 100 mbps download /10 mbps upload from my ISP, and my router's ports are rated to 10/100 mbps (linksys e2500).

 

[DeauteratedDog]

It is almost inconceivable that a router that new wouldn't be full duplex; as bill001g said, half-duplex is pretty much legacy.

But, if you upgrade to a 100 Mbps internet connection, you probably need to upgrade to a router with gigabit ports. Wired specs are closer to reality than wireless specs, but even so, a 100 Mbps Ethernet port won't QUITE reach 100 Mbps, more like 90-something.

 

[ipwn3r456]

Does wiring matter for full-duplex as well?

 

[DeauteratedDog]

No, 100 Mbps Ethernet requires two pairs whether it is half or full duplex; Gigabit Ethernet requires all four pairs. Sometimes you will find a cable with only the 1st two pairs, which will work for 100 Mbps Ethernet, but not gigabit.

 

[ipwn3r456]

Ok then. Thanks for the answers. I don't really mind losing a few megabits, as there are 2 more users in my house that are using the internet as well. Or I can always upgrade to a gigabit router (possible ac routers) for a better connection. Looks like I learned something today.