Does adding switches or hubs to a router slow down intranet traffic?

Assuming modest amounts of traffic (i.e, the amount of traffic itself isn’t a factor), everything is built for the same speed, and good cables, does the number and placement of switches/hubs affect* intra*net speed?

If specifics make a difference, we have a Linksys 310N Gigabit router. Among other things, a D-Link Gigabit switch is connected to it. Another D-Link switch is connected to that switch, and then there’s a small four-port hub connected to the second switch. This all evolved due to changing circumstances and placement—the second switch is two floors down, the little hub is in the middle, but wiring made it connect to the second switch. All of the ports on the router are in use, about six or seven of the top-floor’s switches, 3 or 4 of the second switch’s, and three of the hub’s. The router and two switches are Gigabit, the hub is Ethernet (10/100). All the cables are Cat-6.

Yes.

A few points. “Speed” is a somewhat indistinct term. For most people it means - a metric of how fast their computer works on the network. Network performance comes in two part. Bandwidth and Latency. Bandwidth is the rate at which data is transferred - bits per second. Latency is the time it takes from beginning to send to end of receive to get your data. That is measured in seconds.

A switch, in general cannot work out how to send the data it receives on one port to the port it needs to send it out on in zero time. If it is just a switch, and performs no routing functions it can, in principle, work out where to start sending once it has received the packet header, but that only works if there is no competing traffic trying to send to the same port. In general a switch may need to store the entire packet, and in the case of lots of traffic, may store a number of packets. This adds to the latency.

A router has even more work to do on each packet, since it is required to look inside many packets to work out how and where to send them - it doesn’t just depend upon the Ethernet address (as a switch does), it needs to look at the IP address, and maybe even more. Especially if it must implement any firewall or other functions. This means it must store the packet, work out what to do with it, and then send it. This adds even more latency.

Use of the 10/100 hub is going to be an issue. Being a hub it won’t work full duplex, and it will force all the machines connected to it to share a single half duplex 100Mb/s link.

Gigabit links are pretty sensitive. In order to get anything approaching 1Gb/s you do need to make sure you have good cables and infrastructure. It is pretty common to see actual wire speeds disappointingly less than the theoretical.

I agree with what Francis Vaughan has said, but would add that data density comes into play here. Are you trying to fully leverage the GB throughput? If this is a home/small biz environment, you probably aren’t. Is telepresence/video conferencing or something in play?

In regard to the hub bit, most “hubs” are no longer hubs - hubs do 0 addressing. They just broadcast to every mofo on the network (security FAIL). A switch will direct the data to its (allegedly) appropriate recipient, which reduces traffic significantly.

Dump the hub and replace it with another gigabit switch, for all the reasons stated.

For intranet speed, switches might just speed some activities up a shade because traffic does not necessarily need to go all the way back to the router (through a handful of switches) to get from machine A to machine B, if they are plugged into the same switch.

It’s all going to come down to how many switches lie between two machines (and the router is a switch + NAT firewall + WAP combo).

I doubt you will notice the difference. As long as it’s all gigabit hardware and you have your CAT6 cable, regular latency in the machines will probably dwarf the latency introduced by your switches.

Wow, thanks for the details.

We’re only a two-person house with a home office—that’s where our primary intranet speed-related concerns are. During the day, the two of us are in the office clickity-clacking away. The NAS is in the basement (two floors down) connected to the second Gigabit switch. The primary reason for the Gigabit router/switches is for sharing and storing large files between us—neither of us keeps data locally, it’s all stored on a Gigabit-capable RAID 1 NAS (which itself is backed up to another RAID 1 NAS in a different part of the house). I mention the RAID 1 because I believe it too slows down file transfer speeds, and might make this whole consideration of Gigabit speeds moot.

It’s not unusual to have a few GB transferring between the office and the server, but there is little else intentionally going on in the intranet. At worst someone may be up/downloading a large file from the Internet at the same time or using the VIOP, but heavy combined intra/Internet traffic is probably unusual.

The hub is in the den. The main traffic on it is for streaming Netflix or Hulu. That PC never sleeps, but is (usually) inactive during business hours—when speed would make a difference. The other PCs on the network are like that – used mostly when no one is in the office. Besides, they typically interact with the Internet, and Ethernet speed is far more than what our cable company provides.

Everything is wired with Cat 6.

So copying/pasting a 5 GB set of files goes from PC/Mac->router->first switch->second switch->NAS and back. Does the hub’s relative idiocy make a difference?

(snipped)

The hub shouldn’t be much of a stumbling block in the scenario you describe. It’s kind of like limiting your car to 120 mph. My hunch would be that any latency you’re getting is the result of ISP limitations (or sucktastickness).

There are two other factors: the switch itself can have a maximum throughput (bandwidth), and certain protocols like DHCP can limit the number of hops over which they’ll operate (IIRC it’s 4 for MS DHCP).

Basically, you want a master switch, and all other switches and your internet router should be connected to it, and client devices - PCs, NAS, printers - are connected to those. But I think you’re over-complicating things: it would be simpler to have everything connected to the one gigabit switch. Just buy yourself a decent 16 or 24 port switch. The limit of 100M on the cabling is more than sufficient to cover the house. Something like a Netgear G116.

BTW RAID 1 will speed up file reads and have little or no impact on file writes.

And the sad truth about gigabit NAS is that most of them don’t get close to gigabit speeds. Quite often the speed drops off dramatically with large files.

You might want to check these guys out; they have lots of hard data regarding home networking issues:
http://www.smallnetbuilder.com/

No, this just means that security is not implemented at that layer. It is, very often, implemented at the application layer. This is not usually a problem.