You're probably seeing the impact of out of order packets across the two links--you state you are using variance, which almost assures me they are unequal cost, and out of orders can be very severe on unequal cost links.
I would try CEF, which does per flow load sharing (source/destination address), and then try to see if you get ore throughput when you open two or three ftp sessions through the links, rather than one. If you do only one session, you're not going to see the second tunnel come into play at all with per flow load sharing.
Problem is that the customer wants to copy files from one 2000 server to another 2000 server using the combined 512kbit/s. The drag and drop operation results in a single large MS files copy that is one flow.
Do you think the main problem is oo-sequenced packets. The characteristics of the loadsharing seems almost capped in some way to around 250 kbit/s with packet sizes halving with both tunnels up.
I believe the problem you are observings has to do with your load balancing methods. The GRE Tunnel (regardless what traverses the tunnel) counts as 1 conversation.
By default, your router will do per session load balancing. Where 1 conversation takes 1 path, the next conversation takes the next path.
It is possible that both of your tunnels come up and utilize just one circuit. Depending on what order packets leave your router.
What I believe you want is per packet load balancing, were 1 packet leaving the router goes via circuit a, the next packet going via circuit b?
First, your routing must be set up correctly. The tunnels must load balance per packet on the serial interfaces. that way traffic on any one tunnel will traverse both serial interfaces. Under the serial interfaces, look for a no ip route-cache command.
Then you must load balance via your routing protocol, static? OSPF, EIGRP? to use both tunnels for any given destination. Either one tunnel will use both serial interface, so its not that critical. Or you can further more do load balancing between the two tunnels (that is allready being load balanced across the same two interfaces) on a per packet basis as well, a tad redundant.
Now it is HIGHLY likely packets will arrive out of order. However that is what the sequence number is for in the IP packet.
We are currently running per packet loadsharing with eigrp showing two routes to the remote LAN subnet
The tunnels are running over 2 ethernet interfaces to a pair of local ADSL routers at each site. When we either off-balance the routes by temp changing the bandwidth on 1 tunnel OR shutdown 1 tunnel we get 250kbits down the enabled tunnel. But when we bring up both tunnels we still get an aggregate of 250kbit/s transfer rate shared very accurately across both tunnels BUT the packet size has halved. We notice that the packet per second throughput has doubled but the Bit/s throughput is the same.
2 tunnels, 250kbit/s total @ 41.66 pps with packetsize 850.
We just cannot push the combined rate upwards to 512kbit/s which is what we expect.
We are not seeing fragmentation counts (sh ip traffic)
We have tried setting the DF bit using a policy route map and played with the MTU which all leads to fragmentation
We have also set interface bandwidth to actual bandwidth available via each tunnel
My experience of oos packets is a drop of maybe 10-15% but not 50%
Our customer is not amused andwe have had to abandon similar solutions for other customers. I also noticed doing a search for "ADSL LOAD" on all forums that many others are experiencing such problems so maybe an investigation in the Lab by Cisco may help us all
The problem is still out of order packets, form what you are describing. The traffic originators are probably reducing their TCP segment size in accordance with what gets dropped, and even a 10% to 15% drop rate due to out of orders can cause exactly what you are seeing--a 50% reduction in effeciency across the circuits. TCP is designed to do just what you are seeing--back off heavily--in the face of just about any drop rate, which is why out of orders and single drops have such a disproportionate impact on performance.
I'd simply not use per packet load sharing on these links.
This is actually a pretty cool feature, i didn't even know it existed until I was looking for a solution to advertise a subnet (prefix in BGP talk), only if a certain condition existed. This is exactly what conditional advertisements does
j ai une question j ai achete un routeur cisco 887VA-k9 , je le configuré avec la configuration ci- dessous
si je le lier avec mon pc portable sur l un de ses ports directement ça marche toute est bien ( la connexion internet + m...
Attached policy provides CLI access to the Cisco 4G router over text messaging. Two files are in the attached .tar file:
2. PDF with instructions on how to load and use the .tcl file.