I cannot say with 100% certainty, but you may get more useful test data by running TTCP, as opposed to pings or extended pings. This will also more closely mirror the intended test environment where the expectation will be high for TCP based traffic.
Do you have a copy of the configs for posting? v/r, Paul Werner > A couple of weeks ago there were a couple of discussions on this board > about > using multiple T1's to improve data throughput. If memory serves, there > were > two possible ways to do this: 1) per packet load sharing and 2) PPP > multilink > > for no particular reason I decided to do a little study on PPP > multilink. > Well, OK, I do have two particular reasons - an upcoming Lab and a > customer > who is asking about this. > > So, I build a scenario as follows: > > serial0 token ring > R6--------R5-----------R4 > |--------| > serial1 > > to test throughput, I used extended ping, with multiple pings and > various > size payloads, from a loopback on R4 to a loopback on R6. > > the routing protocol was EIGRP, done to assure per packet routing > between R6 > and R5 as a control. > > My results were interesting, to say the least. unexpected, but so > consistent > that there is no question, in my mind, anyway, about some of the > assumptions > many of us make about various load sharing and multiplexing options. > > a summary of the results are using the Cisco router reporting of > min/avg/max round trip times - the middle number is the one to watch. > > packet size PPP multilink single serial link configured as PPP > multilink > > 1000 24/24/132 20/20/104 > > 1500 28/29/52 24/27/112 > > 500 16/19/64 12/13/104 > > 64 12/14/60 4/7/104 > > note that in every case, the single link, configured for PPP multilink, > is > SIGNIFICANTLY faster than the dual link. > > Interesting. So I constructed some further experiments, using extended > ping, > multiple packets of variable size - range 64 to 1500: > > PPP multilink per packet load share single T1 > > 8/17/136 4/17/136 4/17/144 > > these figures are from over 15,000 pings per scenario, so it is not a > case > of random chance here. there is no difference whatsoever between the > results > of a single serial link, per packet load sharing over two serial links, > and > PPP multilink. what is most surprising is that a single serial > connection > proves JUST AS FAST as a dual serial connection. > > Now what I conclude from this is an opinion that multiple T1's DO NOT > really > do much for you in terms of more bandwidth. At least for the kinds of > data > flows I am able to generate in the lab. Furthermore, PPP multilink is > actually harmful to throughput. So I gotta ask - is load sharing really > adding anything to the mix? Really? In real world scenarios and data > flows, > where is it that you are gaining anything? > > Lastly, I set up a final scenario in which I sent 5000 byte packets. > this > means fragmentation and reassembly would occur, because the MTU on all > wan > interfaces is 1500 bytes. Here are the results when pinging 5000 times > using > a 5000 byte payload: > > single serial link: 64/66/168 > > per packet load share: 64/64/168 > > ppp multilink: 48/52/172 > > note here that the load sharing scenario is slightly faster than the > single > serial link, and that the ppp multilink is FAR AND AWAY faster that the > other two. I suspect the reason for this is efficiencies gained under > the > multilink scenario when fragmenting and reassembling the oversized > payloads > > In any case, I hope this presentation will lead to some good discussion > of > bandwidth and results. would it be fair to suggest that peoples' efforts > to > solve what they perceive as bandwidth issues by implementing multiple > WAN > links is really a study in fruitless activity? > > Maybe I should have set up some IPX scenarios? ________________________________________________ Get your own "800" number Voicemail, fax, email, and a lot more http://www.ureach.com/reg/tag Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=21701&t=21701 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
