100mb/s network operates at 10mb/s ????

[Krisbee]

This is probably an old chesnut, and has not really concerned me in the past. But  I'm trying to setup a PC as a central backup point for the home and have found network throughtput to be much lower than the advertised 100mb/s, in fact is more like 10mb/s.  First thoughts were that not all NICs etc were operating at 100mb/s full duplex, but they do appear to be correctly set.

I have two Pcs with wired connections to the LAN side of my router which acts as an auto-sensing 10/100mb/s switch.

The ethtool output on the two Pcs is:

Code: [Select]

ethtool eth1
Settings for eth1:
        Supported ports: [ MII ]
        Supported link modes:   10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
                                1000baseT/Full
        Supports auto-negotiation: Yes
        Advertised link modes:  10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
                                1000baseT/Full
        Advertised pause frame use: No
        Advertised auto-negotiation: Yes
        Speed: 100Mb/s
        Duplex: Full
        Port: MII
        PHYAD: 0
        Transceiver: external
        Auto-negotiation: on                                                                                                                                 
        Supports Wake-on: g                                                                                                                                 
        Wake-on: d                                                                                                                                           
        Link detected: yes         
and

Code: [Select]

ethtool eth0
Settings for eth0:
        Supported ports: [ MII ]
        Supported link modes:   10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
                                1000baseT/Full
        Supports auto-negotiation: Yes
        Advertised link modes:  10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
                                1000baseT/Full
        Advertised pause frame use: No
        Advertised auto-negotiation: Yes
        Speed: 100Mb/s
        Duplex: Full
        Port: MII
        PHYAD: 0
        Transceiver: external
        Auto-negotiation: on
        Supports Wake-on: g
        Wake-on: d
        Link detected: yes

The router's LAN side connections also appear to be operating at 100mb/s full duplex.

Code: [Select]

>eth device iflist
Interface       Type            Result          State         
ethif1          auto            100BaseTFD      UP [forwarding]
ethif2          auto            Not connected   UP [forwarding]
ethif3          auto            100BaseTFD      UP [forwarding]
ethif4          auto            100BaseTFD      UP [forwarding]
From the router CLI manual: 100BaseTFD: 100Mb/s communication speed in full duplex mode.

Any ideas why the actual tthroughput is so low? Are the m/board NICs on both machines useless? Is this the best I can expect?

[T6]

what type of cable are you using, utp cat 5E or 6 or 6E?

the slow speeds you mention, where are being reported?

remember that a ethernet adapter at 100megabits is only running at 12 megabytes per second, megabit is not the same as a megabyte

1 millon bits is only 128000 kilobits

[Krisbee]

OK, this is my misunderstanding about what 100base-TX means.  If the theoretical max file transfer speed is just 12.8Mb/s, I need a re-think about what I'm doing. 

[menotu]

OK, is this my misunderstanding about what 100base-TX means? Is the theoretical max file transfer speed just 12.8Mb/s? I need a re-think.

Yes, basically - divide by 8 and it will give you a reasonable average (overhead and other things come into play) but that division is fairly good. (just remember, 8bits to 1 byte)

If I got 11MB (bytes) from 100Mb (bits) I would be more than happy

Often users see 100Mb (bits) and think wow, that's super fast, but when converted to bytes it drops it down and people often feel short changed over it.

[T6]

yes, type of cable, connector, adapter, router and or switch often will make change this number

usually you get 10 megabytes per second

[The Chief]

OK, this is my misunderstanding about what 100base-TX means.  If the theoretical max file transfer speed is just 12.8Mb/s, I need a re-think about what I'm doing. 

As a rule of thumb (no, not always true) when you see a lower case 'b' it is referring to bits, and when you see an upper case 'B' it is referring to bytes.

Similar with the 'M'.  An  upper case 'M' indicates Mega (or millions) and a lower case 'm' indicates Milli (or thousandths) - quite a jump, a difference by a factor of one billion.