Understand a major difference....

AT&T for example sells GB fiber for $8000 per month. But they are selling layers 2 end to end to the subsciber. So because GB fiber is the customers first HOP, the customer's MTU can adjust to 9600MTU jumbo frames. For example if the customer has a GB switch on premise, they are already using Jumbo frames, and easy to interface to GB Ethernet WAN connection. The other LECs doing GB fiber are often using something other than Ethernet, such as Sonet, ATM, or whatever. There may be something there taht deals with it.

The problem I brought up is that ISPs hookkup the customer's initial connection with less than 100mbps which is NOT Jumbo frames. The reason is that most Ethernet Fiber/CAT5 (<100mbps) equipment does not allow over 1500MTU, and only a few equipment manufacturers even support allowing allow around 1540 MTU to supprot things like MPLS and VLANs.

I do not believe that people like ATT&T are passing over 200mbps on their GB Ethernet fiber links, when they are using them as backbones or extensions to existing customer's connection, for the reason I brought up. I just don't think that the end user custoemr base is smart enough to know the difference.

Tom DeReggi
RapidDSL & Wireless, Inc
IntAirNet- Fixed Wireless Broadband


----- Original Message ----- From: "Travis Johnson" <[EMAIL PROTECTED]>
To: "WISPA General List" <wireless@wispa.org>
Sent: Saturday, January 06, 2007 11:42 PM
Subject: Re: [WISPA] Optimally taking advantage of GB Ethernet


Tom,

How are the "big boys" doing it? Surely AT&T and others are transporting more than 200Mbps across their 1GB fiber links.

Travis
Microserv

Tom DeReggi wrote:
Gigabit Ethernet, can pass 1 gbps when it uses greater than a 9600 MTU frame.
But with a 1500MTU frame, it can barely pass 200 mbps.
The problem is that most Internet and subscriber traffic is using a 1500MTU or smaller frame. So in theory, its would be just as efficient and fast to bond two 100 mbps fiber connections than it would to buy 1- 1GB fiber connection.

So the question is.... How do we most efficiently use 1GB fiber to get the advantage of the full 1GB of capacity?
Do we need to use some sort of packet agreegation/stuffing technology?
Is GB etherner pointless for Internet transit backbones?
Is GB just good for high capacity Transports, recognizing that routers will likely split traffic to different smaller bandwidth peers?
Is there a special router or router feature used to solve this problem?
Is that method available to Linux?

The reason I ask is several fold. In a network design where all traffic flows to a single source (for example many 100mbps baclhauls to remote areas to 1 central data center), it would be beneficial because the cost of 1 big 1GB pipe could be shared to deliver capacity to everything, better apt to handle peak traffic and get higher oversubscription rates. However, if teh GB INternet pipe can not be efficiently used, this method would be severally flawed. It might be better to have multipel 100mvps transit connections spread out across one's network, so there was a shorter path to transit, and the network's bandwdith spread out amungst multiple 100mbps transit connection, for better over all throughput. In other words, in a 10 city network, 1- 100mbps pipe in each of teh 10 cities would allow a full combined 1 gbps of Internet transit, where as agregating 100mbps from each city to one central source where their was a single 1GB transit, would result in only a 200mbps throughput, assuming traffic was delivered to it as a 1500 MTU.

Any feedback?

Take note that my comment that a 1500MTU frame 1 Gbps Ethernet card could only pass 200kbps was based on some lab tests. With the 1500MTU frame acheiving only 200kbps, our routers CPU utilization was less than 20%, so it was not a saturated router. The second we changed MTU to 9600, we got over 800 mbps, and CPU utilization was still very low, forget exact number but under 40%. These tests were replicated going PC to PC (no switch) and with a high end SMC GB switch in-line.

Tom DeReggi
RapidDSL & Wireless, Inc
IntAirNet- Fixed Wireless Broadband
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