Dynamic Fragmentation

Posts: 17 · Posted: Wed Oct 11, 2006 7:25 pm Post subject: Dynamic Fragmentation

I have a Linksys DI-724U which has the StreamEngine QoS technology. One of the QoS options is to use "Dynamic Fragmentation" and when I check the help file here is the info:

Dynamic Fragmentation
This option should be enabled when you have a slow Internet uplink. It helps to reduce the impact that large low priority network packets can have on more urgent ones by breaking the large packets into several smaller packets.

My question is: can anyone define for me "a slow Internet uplink"? What speed is considered to be slow/fast?

Posts: 4751 · Vonage Forum **MVM** Joined: Aug 30, 2005 Posts: 4751

That's a question with no clear-cut answer, but I'd call any cable service slower than 1 Mbps down and 200 kbps up slow. Halve those for DSL. As far as the fragmentation thing is concerned, if you think your service may qualify as slow, then give it a try. If it helps, it helps.

Posts: 17 · Posted: Wed Oct 11, 2006 7:53 pm Post subject:

Steve48 wrote:

That's a question with no clear-cut answer, but I'd call any cable service slower than 1 Mbps down and 200 kbps up slow. Halve those for DSL. As far as the fragmentation thing is concerned, if you think your service may qualify as slow, then give it a try. If it helps, it helps.

Right now I have 10 MB down and 1.5 MB up, but with that definition by Linksys I have no idea what they mean by slow. Slow compared to what? Dialup?

Posts: 4751 · Vonage Forum **MVM** Joined: Aug 30, 2005 Posts: 4751

They probably mean slow compared to whatever you need for what you're doing. In the world of VoIP, 90 kbps would be about as slow as you can stand. By that standard, your service is very fast.

Posts: 37 · Vonage Forum Junior Joined: Nov 16, 2005 Posts: 37

You need to fragment with VoIP on any upspeed link slower than 1.5mbps. Technically anyway.

Slower than 1.5mbps and that actual time it takes to physically put the data on the line can delay voice packets. A 1500kbps data packet on a 256kbps link can take quite a while to physically get out on the wire. Fragmentation solves this by chopping up the packets into smaller chunks.

This is most common in the business world where a large amount of data might also be transfering across the same slow link. Common methods are FRF.12 and MLPPP LFI.

Posts: 533 · Posted: Thu Oct 12, 2006 9:39 am Post subject:

Celeron wrote:

You need to fragment with VoIP on any upspeed link slower than 1.5mbps. Technically anyway.

Slower than 1.5mbps and that actual time it takes to physically put the data on the line can delay voice packets. A 1500kbps data packet on a 256kbps link can take quite a while to physically get out on the wire. Fragmentation solves this by chopping up the packets into smaller chunks.

This is most common in the business world where a large amount of data might also be transfering across the same slow link. Common methods are FRF.12 and MLPPP LFI.

Hmm, I'm thinking 1.5Mbps is too high to implement any fragmentation or interleaving. Cisco's recommendation is anything slower than 768Kbps. FRF.12 is for frame relay, LFI is generally used for BRIs. For Cable or DSL, you would generally adjust the tcp MSS down to about 542 Kbps.

Just as an FYI, this is called serialization delay, or blocking delay.