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RE: Can this design work for ISP connection? [7:95111] posted 12/06/2004
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--On 06 December 2004 23:31 +0800 Nuurul Basar 

> Peter,
> Thanks for the URL, so any load balancing is needed it must used
> rip, eigrp or ospf

"or derived from statically configured routes and packet forwarding 

What matters is, what goes into the

> and I believed both way that is the customer
> router and the ISP routers.  Only with this than both incoming and
> outgoing packet will be routed evenly between 3 x 2mbps link.
> Load balancing also will allowed full utilization of all 3 link and
> then may be the customer will see some different.  Hope this is
> correct.

You can never get truly 100% balanced and guaranteed load balancing.

Unless you are using multilink ppp or some form of per packet load 
balancing then you will often find that certain flows of traffic will 
tend to favour one outbound and one inbound link.

You need to consider traffic in each direction

	Inbound (to your customer) link choice will be dictated by the 
configuration at the ISP

	Outbound (from your customer) link choice will be dictated by the 
customer router.

If you use per destination load balancing then

"This preserves packet order, with potential unequal usage of the 
links. If one host receives the majority of the traffic all packets 
use one link, which leaves bandwidth on other links unused. A larger 
number of destination addresses leads to more equally used links."

This can be particularly relevant if your customer is using a single 
outbound NAT address and the ISP router is configured for per 
destination load balancing.

If you use per packet load balancing then you are more likely to 
evenly utilise the links but this could have a negative effect on the 
performance of the router which could result in poor packet 
throughput and an inability to fully utilise the links.  I would 
suspect that a number of 2600 series router models would be unable to 
handle 5-6mbs of per packet load balanced traffic.



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