I'm currently studying for the Cisco ONT exam, much of which relates to Quality of Service (QOS). I'm trying to get some of the basic principles clear in my mind.
Two things which I'm not sure of are the 'Link Efficiency Mechanisms' of compression and LFI. Would I be correct in the following two statements?
1). Compression (RTP header compression, TCP header compression, payload compression, Stacker & Predictor) should not be used (unless the data is being sent over a line of below 768Kbps bandwidth for software compression or a line of below 2Mbps if done in hardware). These days lines of this little bandwidth are very uncommon and so I take it that compression in this instance is really a thing of the past in most organisations (assuming there are no lines of this little bandwidth).
2). LFI (Link Fragmentation and Interleave) where, if you're running VOIP, you can turn on LFI so that large data packets are split into fragments and voice packets slotted between the fragments to reduce delay and jitter: This should not be used either unless you're doing it on a link of below 768Kbps.
Basically, if I'm looking to implement QOS and make the network more efficient should I not even bother to think of Compression or LFI unless I've got very slow links to implement them on? All the documentation I've read so far says not to. However, I was thinking, what if you've got a 10 or 100Mbps link and it's running at high utilisation maybe 60 - 70% much of the time and perhaps you're running voice over it, then wouldn't it be better to at least implement header compression so that the bandwidth usage would go down, so then wouldn't this cause less packets to be dropped from the output queues or eliminate the dropping altogether?
Thanks for any replies,