Gigabit Ethernet Switch

nicho

macrumors 68030
Original poster
Feb 15, 2008
2,862
1,364
When we bought our flat, the one thing I insisted on as part of our refurbishment was having ethernet cables run to each of the bedrooms, knowing that wifi would be a bit shaky thanks to thick walls and/or interference from neighbours. Since then my ISP has improved internet speeds from 100meg to 200meg to 200meg+ (sometimes it reaches 450mbps) so I'm really digging having gigabit ethernet to the computer in my bedroom.

However, I'm seriously regretting only having one ethernet socket in here. Wifi to the apple tv & internet connected tv can be spotty at times. I also want to be able to hook up a laptop to ethernet at my desk, since it looks like I'll be working from home for a while. But I only have one port.

If I use an unmanaged gigabit ethernet switch, what impact will that have on network speeds for my mac mini (which currently reaches up to 115MB/s or so to my other mac mini/media server)? How do two gigabit ethernet capable devices share network bandwidth when A) one is transferring files but the other not doing much or B) both are trying to transfer amounts of data? If they both go 50/50 it would be OK, if one could take priority over another and screw over my mac mini... I'd be best off sticking to wifi on my laptop i guess!

How do 10/100 devices affect a gigabit network switch? Would hooking up my old apple tv to one port slow down the gigabit connection of my mac mini in any significant way?
 

techwarrior

macrumors 65816
Jul 30, 2009
1,130
415
Colorado
First, it is important to distinguish between speed and capacity. Most of us think of network "speed" as how fast the data traverses the wire (or airwave). But, really, network "speed" is a measure of capacity. Think of a straw and hose. Water (electrons in networks) may travel through each at the same speed, but the hose (1Gbps port) has more capacity so filling a bucket with a hose will go much faster than with a straw. The speed to fill the bucket therefore, is derived from speed the water travels, and the capacity of the delivery system. Network speed is really a measure of how much data can be transferred in a given period of time, or the capacity of the pipeline.

The uplink will have a capacity of 1Gbps. Each client can do up to this, and collectively, all hosts on that node can use up to the 1Gbps capacity of the uplink. But the slowest link in the chain (your ISP) will reduce each session down to that level. So, theoretically, two hosts each sharing 115Mbps of ISP bandwidth would leave plenty of capacity on the uplink between the router and switch.

Switches typically have more backplane capacity than individual ports. So if two hosts on the same switch, which don't require the uplink to exchange data, could theoretically transfer up to 1Gbps between them, while another host is downloading at ISP speeds from the internet. The ports on the switch, and not the switch itself are the restricting piece of it.

10/100 hosts will negotiate transmit rates with the switch for their respective ports. So the switch will send and receive on that port at whatever rate the two negotiate. That leaves more capacity for the other hosts on the switch.

Basically, you may be overthinking this. A switch will allow multiple hosts to share the uplink, and with few exceptions, none of the hosts will actually use even close to the uplink capacity. The ATV will not negatively impact the other hosts, ATV 4 and earlier will rarely use more than 5Mbps while streaming. 4K content might use 10-15Mbps, but again that should not be noticeable. This is true be it content from a local media server, or through the ISP link.

Most other internet uses, web pages, emails, etc will only use a small amount of the capacity at any given time. Even large file downloads won't use the full capacity, the remote host may also have a "slower" uplink, plus the data must share the wire with everyone else using the networks between you and the file server.

In short, the slowest link in the chain is the restricting point. In almost all cases, this will be the ISP link. The switches and routers will give you more than enough capacity.
 

nicho

macrumors 68030
Original poster
Feb 15, 2008
2,862
1,364
First, it is important to distinguish between speed and capacity. Most of us think of network "speed" as how fast the data traverses the wire (or airwave). But, really, network "speed" is a measure of capacity. Think of a straw and hose. Water (electrons in networks) may travel through each at the same speed, but the hose (1Gbps port) has more capacity so filling a bucket with a hose will go much faster than with a straw. The speed to fill the bucket therefore, is derived from speed the water travels, and the capacity of the delivery system. Network speed is really a measure of how much data can be transferred in a given period of time, or the capacity of the pipeline.

The uplink will have a capacity of 1Gbps. Each client can do up to this, and collectively, all hosts on that node can use up to the 1Gbps capacity of the uplink. But the slowest link in the chain (your ISP) will reduce each session down to that level. So, theoretically, two hosts each sharing 115Mbps of ISP bandwidth would leave plenty of capacity on the uplink between the router and switch.

Switches typically have more backplane capacity than individual ports. So if two hosts on the same switch, which don't require the uplink to exchange data, could theoretically transfer up to 1Gbps between them, while another host is downloading at ISP speeds from the internet. The ports on the switch, and not the switch itself are the restricting piece of it.

10/100 hosts will negotiate transmit rates with the switch for their respective ports. So the switch will send and receive on that port at whatever rate the two negotiate. That leaves more capacity for the other hosts on the switch.

Basically, you may be overthinking this. A switch will allow multiple hosts to share the uplink, and with few exceptions, none of the hosts will actually use even close to the uplink capacity. The ATV will not negatively impact the other hosts, ATV 4 and earlier will rarely use more than 5Mbps while streaming. 4K content might use 10-15Mbps, but again that should not be noticeable. This is true be it content from a local media server, or through the ISP link.

Most other internet uses, web pages, emails, etc will only use a small amount of the capacity at any given time. Even large file downloads won't use the full capacity, the remote host may also have a "slower" uplink, plus the data must share the wire with everyone else using the networks between you and the file server.

In short, the slowest link in the chain is the restricting point. In almost all cases, this will be the ISP link. The switches and routers will give you more than enough capacity.
You're right in that i'm probably overthinking it! I didn't realise that two computers connected to the same switch could talk to each other directly without having to go back through the router.

I very rarely max out the 1gig pipeline right now, and even when I do (sending reencoded files back to my media server) it's not exactly mission critical stuff or my job (where time = money)...

Thanks
 

4sallypat

macrumors 6502
Sep 16, 2016
403
378
So Calif
Glad to see there are people that prefer to hardline into a network.

At home and work, I always use gigabit LAN whether it's direct to port or thru a dongle / adapter.

Many people still think wireless is fast and flawless....
 

techwarrior

macrumors 65816
Jul 30, 2009
1,130
415
Colorado
You're right in that i'm probably overthinking it! I didn't realise that two computers connected to the same switch could talk to each other directly without having to go back through the router.

I very rarely max out the 1gig pipeline right now, and even when I do (sending reencoded files back to my media server) it's not exactly mission critical stuff or my job (where time = money)...

Thanks
Switches (as opposed to hubs) learn the IP address and MAC address of any connected host, and store the info in an ARP database. Hubs just send everything to everyone connected to it and hope someone knows what to do with it, a hot mess!

Switches route packets using Layer 2 addresses (MAC Address), routers use Layer 3 (IP Addresses). So, by knowing which port an IP\MAC address is connected to, the switch can send traffic to the one port and not bother the other ports. When two hosts connected to the same switch have data for each other, the switch forwards to the intended host directly, without bothering other hosts or the router.

Typically, a 4 port Gbps switch will have capacity to handle something like 2-3Gbps internally (simultaneously) while limiting the amount of data sent on any one port to 1Gbps (the Ethernet cable and Network interfaces on connected devices will typically only be able to handle 1Gbps anyway).

So, you could be using close to 1Gbps transferring a file from A to B, and still stream 5Mbps to the ATV and there will be no hiccups, and the uplink from the router would only be using the 5Mbps streaming to the ATV.
 
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