Link Aggregation - EtherChannel Question - Probably Stupid

[Iluvnetwork]

Yesterday, I learned about the link aggregation. Today, I called the tier 1 bander and   asked whether it is possible to buy two Gigabit services and they can combine the two gigabit lines into one logical line so that I can enjoy 2 Gbps speed. The manager said it is not possible. He didn't explain to me why it is not possible. If you know why could you please explain to me why it is not possible? 

[Flavio Miranda]

Hi @Iluvnetwork

 This is possible and that's why Etherchannel is used for.

-If I helped you somehow, please, rate it as useful.-

[Joseph W. Doherty]

In theory it's possible, but you generally need to use the same device on both ends of the port-channel. This may be a problem for your provider.

Also, something like port-channel often uses special control packets which sometimes have issues on MetroE links.

Lastly, port-channel provides aggregate bandwidth, but individual flows will only use one link. (I.e. you might not get to enjoy extra bandwidth as you think.)

[Iluvnetwork]

My understanding:
Maximum bandwidth per flow won't be increased; however, I can enjoy the extra bandwidth if load balancing happens optimally. Right?

[Joseph W. Doherty]

Correct, although even "optimal" load balancing isn't a sure thing.

Etherchannel load balances flows across the links without considering actual current link loading. I.e. it's possible two flows can hash to the same congested link while another link is not being used. Because of this, a dual Etherchannel might only average about 50% more effective bandwidth.