A Few Questions On Gigabit Switching.

nelson.garcia · ‎06-17-2010

As I sit here considering products to further implement into my company's network and looking into new designs I have to take into consideration bandwidth utilization averages of our current switches. I say I must consider this because the price of Cisco products go much higher when talking about gigabit technology as opposed to 10/100 Mbps switches.

What I want to specifically speak on are Access Layer switches, or end user switches. As I study more and more into Cisco, I begin to think back on some of the purchases I made on behalf of my company and I kinda begin to see where I may have went wrong; for example, purchasing a 24-port 3560G for users who won't ever use half that bandwidth, especially when most of the traffic transmitted and received is out of one VLAN on one switch. What I mean is, I have a about 100 people across 7 locations accessing one server VLAN most of the time. I understand why I would need gigabit trunks, but for end users that may access the servers sporadically, gigabit ports don't make much sense. I see where I could have gotten away with using a 10/100 switch using gigabit uplink ports for end users.

Who are these end users and what type of applications or network setup would have to be put in place to justify purchasing a gigabit switch at the access layer?

I feel like for most flat networks, especially at the access layer, 10/100 would suffice for most people.

On one of my 48 port 3560G switches, which has the servers and some users on it and is fully populated, when I issue the "show controllers utilization" command, I see "0" all across the board.

Another test I performed to measure bandwidth utilization a port that connects to our busiest server, I did as follows.

"clear controllers utilization"

waited 8 seconds

"show controllers utilization"

What I got in the total transmit column was 19622194 Bytes which translates to roughly 150 megabits transmitted over 8 seconds. if I divde that by 8, I get roughly 18 megabits per second, nowhere close to full capacity of a port on a 10/100 switch.

I'm not sure if I'm going at this the wrong way, or if my measurements are off, but I hope I can get some good feedback from some of you guys regarding the implementation of gigabit switching. It could definitely save people a lot of money.

Thanks for listening, everyone.

darren-carr · ‎06-17-2010

Hi Nelson,

Your points are good and valid. I see the same performance across our LAN's on a daily basis.

I guess if you go back five years when the major reason that people stayed with 10/100 was cost i.e. the cost of a gigabit port on a switch. These days, with regards to the price comparison, the difference isn't all that much.

The way I view it is, yes you will pay more for your gigabit ports, and yes (today) you don't see performance getting anywhere close to what the hardware is capable of, but what you do have is capacity. You have capacity to grow your LAN, extend it, etc. You are providing an environment that is easy to grow/expand and that can support the short-term goals of a business. Most new switches also provide an upgrade path now to 10Gbps through GBIC's, etc, that are pretty painless to deploy.

I wouldn't feel guilty. Cost differences between most switches now (10/100-1000Gbps) are not that significant. I think you will find most engineers will always try to plan for an increase in capacity and growth.

Ganesh Hariharan · ‎06-17-2010

As I sit here considering products to further implement into my company's network and looking into new designs I have to take into consideration bandwidth utilization averages of our current switches. I say I must consider this because the price of Cisco products go much higher when talking about gigabit technology as opposed to 10/100 Mbps switches.

What I want to specifically speak on are Access Layer switches, or end user switches. As I study more and more into Cisco, I begin to think back on some of the purchases I made on behalf of my company and I kinda begin to see where I may have went wrong; for example, purchasing a 24-port 3560G for users who won't ever use half that bandwidth, especially when most of the traffic transmitted and received is out of one VLAN on one switch. What I mean is, I have a about 100 people across 7 locations accessing one server VLAN most of the time. I understand why I would need gigabit trunks, but for end users that may access the servers sporadically, gigabit ports don't make much sense. I see where I could have gotten away with using a 10/100 switch using gigabit uplink ports for end users.

Who are these end users and what type of applications or network setup would have to be put in place to justify purchasing a gigabit switch at the access layer?

I feel like for most flat networks, especially at the access layer, 10/100 would suffice for most people.

On one of my 48 port 3560G switches, which has the servers and some users on it and is fully populated, when I issue the "show controllers utilization" command, I see "0" all across the board.

Another test I performed to measure bandwidth utilization a port that connects to our busiest server, I did as follows.

"clear controllers utilization"

waited 8 seconds

"show controllers utilization"

What I got in the total transmit column was 19622194 Bytes which translates to roughly 150 megabits transmitted over 8 seconds. if I divde that by 8, I get roughly 18 megabits per second, nowhere close to full capacity of a port on a 10/100 switch.

I'm not sure if I'm going at this the wrong way, or if my measurements are off, but I hope I can get some good feedback from some of you guys regarding the implementation of gigabit switching. It could definitely save people a lot of money.

Thanks for listening, everyone.

Hi,

Your assumption is right with end user access layer switches with 100 Mbps of traffic but at server end it is required to be 1 Gb port as traffic hits at server from all location so the bandwidth can go higer depend upon the application funcationality.But following are the points in which gig network are been introduce over the Mbps network:-

Gigabit Ethernet builds on these proven qualities, but is 100 times faster than regular Ethernet and 10 times faster than Fast Ethernet. The principal benefits of Gigabit Ethernet include:

    * Increased bandwidth for higher performance and elimination of bottlenecks
    * Broad deployment capabilities without re-wiring, using 1000BASE-T Gigabit over Category 5 copper cabling
    * Aggregate bandwidth to 16Gbps through IEEE 802.3ad and Intel® Link Aggregation using Intel server adapters and switches
    * Full-duplex capacity, allowing data to be transmitted and received at the same time so that the effective bandwidth is virtually doubled
    * Quality of Service (QoS) features which can be used to help eliminate jittery video or distorted audio
    * Low cost of acquisition and ownership.

Hope to Help !!

Ganesh.H

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