Latency difference between copper and fibre

[Mturner]

HI all, had a strange request from a manager here to find out whats better fibre or copper , we have a large wan useing either copper or fibre, we need to know whats better, does anyone know any good websites etc or can give any advice to get me going on this.
also were implementing les circuits now so instead of routers were be movning on to switches, he wants to know what a switch does that a router doesnt in terms of latency and vise versa.
thanks for any help!!

Marc

 

[jimbopalmer]

The 'speed of light' is measured in a vacumn, the speed of light in network fiber is aboout 60% of the speed of light. The speed of electricity in copper wire is nearer to 75% of the speed of light. Over any reasonable distance, nether will be measurable by the users.

(Over unreasonable distance, you will use fiber anyway, you can get single mode fiber to fo 125 km at gig speeds, copper at gig speed will do 100 meters that distance)

Converting from fiber to copper can happen in 450 nanoseconds so that should not be an issue

Fiber is also harder to tap and less prone to interfence, but you knew that.

I tried to remain child-like, all I acheived was childish.

 

[Mturner]

all very good info, thanks for that, keep it coming though!

 

[bierhunter]

You also have to remember that the speed of data is not the same as the speed of light or electricity. One is the carrier and one is the data.

Data traveling at 1Gbps in light is the same as 1Gbps in electricity. Fiber vs. copper really depends upon the requirements of the network. Personally, I like fiber on the backbone.

You'll also need to think about cable maintenance. Who is going to support the cabling? Can your team do fiber terminations? Do they have the tools and training? If not, and if the length allows it, can you use copper?

Routers vs. switches, the switches should be faster. And, if you have multiple vlans, you can speed up layer-3 routing by using multilayer switching. But...if you have multiple subnets/vlans, you will need a layer-3 capable device. But you can have that built-in to your switch.

BierHunter
CNE, MCSE, CCNP

 

[Mturner]

Hi thanks for all the replys.
ill give you all a basic over run of the network
currently we have a core site, which has multiple bt megastream links out to area hub sites, then remote sites have megastream links to the area hubs, this is all done though nortel arn's ar the remote sites, nortel asn's at the hub sites and nortel bcn's at the core, obviously this is routed.
what we are planning on doing is having bt les circuits to the area's and remote sites but not useing routers anymore, using cisco layer 3 switches with vlans.
bt les circits have to be fibre links.
what i have got to find out is what the advantages of this new infrastructure is and at what points the advantages kick in, eg is the advantage going to be the fibre cabling instead of the copper or is the advantage going to be the swiches over routers.....

any comments welcome!
Marc

 

[Mturner]

Has anyone got any comments on why switching is better than routeing?
many thanks

Marc

 

[Chr1sUK]

Correct me if I am wrong, but arn't they totally different?

I always thought they were! :S

If you replace your routers with switches....what's going to route the packets in and out?

I have probably got the wrong end of the stick mind you, but it's good to learn new things

 

[smegecki]

as far as i know you need both router and switch

what you don't want is a broadcast hub.

a switch sends the packet meant for a particular machine directly to it

a hub broadcasts the packet meant for a particular machine to all machines, the specific machine knows the message is for it a grabs it

as we know broadcast messages tie up network bandwidth

note definitions below from

http://www.webopedia.com

Router

(row´ter) (n.) A device that forwards data packets along networks. A router is connected to at least two networks, commonly two LANs or WANs or a LAN and its ISP’s network. Routers are located at gateways, the places where two or more networks connect.
Routers use headers and forwarding tables to determine the best path for forwarding the packets, and they use protocols such as ICMP to communicate with each other and configure the best route between any two hosts.

Very little filtering of data is done through routers.

Switch

1) In networks, a device that filters and forwards packets between LAN segments. Switches operate at the data link layer (layer 2) and sometimes the network layer (layer 3) of the OSI Reference Model and therefore support any packet protocol. LANs that use switches to join segments are called switched LANs or, in the case of Ethernet networks, switched Ethernet LANs.

hub=bad

A common connection point for devices in a network. Hubs are commonly used to connect segments of a LAN. A hub contains multiple ports. When a packet arrives at one port, it is copied to the other ports so that all segments of the LAN can see all packets.

 

[jimbopalmer]

in general, enterprise routers are software running on expensive general purpose hardware and allow modular WAN interfaces.

a layer 3 switch typically uses cheap ASIC hardware routing and only offers ethernet ports.

Both do routing, but the router is slower and more flexible while the layer 3 switch is faster and more limited in hardware protocols.

if your WAN appears to be ethernet to the switch a layer 3 switch could replace a router and be cheaper and faster.

I tried to remain child-like, all I acheived was childish.

 

[Chr1sUK]

Ahh, I see.

Thanks for clearing that up Jim!

 

[Mturner]

we will be using layer3 switches instead of routers, advantage being is we can vlan them and give a site say 1 network or up to 24 diffrent networks/

the switches will be Cisco Catalyst 355024