Performance Difference Between Bonded 4 x T1 and 6 Mb/s Fiber

[Michael Darr]

Can anyone tell me the difference in throughput between a bonded T1 (4x) solution (6 Mb/s bandwidth) and a single 6 Mb/s fiber solution.  How could I possibly measure this?

[Joseph W. Doherty]

What particular bonding technology?

Bonding often uses some bandwidth and may add to CPU load to the devices on the two ends of the link and might add latency.

What kind of 6 Mbps fiber technology?

Often something like 6 Mbps would be provided as some fractional bandwidth on a "faster" link that polices the committed rate.  Policing is often harsher on the traffic than on a link that natively supports the bandwidth as a natural clock rate.  I.e. policing might reduce actual transfer rate less than its offered/provided/supported bandwidth.

You could compare the two technologies using various bandwidth test tools.  Depending on how the technologies are configured, and how your bandwidth tools test, you may see very little difference or a noticeable difference for different bandwidth tests.

[Michael Darr]

Thanks for responding, Joseph.  The topology is 4 T1's connected to a Cisco 1921 router.  The router is doing the bonding.  I can ask our ISP for additional information if you need it.  The application in question is VoIP.  We are losing so many frames that the conversations are often unintelligible.

The 6 Mb/s fiber is hypothetical, trying to compare the technologies based upon the equivalent fiber capacity to 4 x bonded T1's.

[chrihussey]

A bit off topic, but are you doing PPP multilink between two routers? If so do you have interleave configured and a service policy in place?

http://www.cisco.com/c/en/us/td/docs/ios/12_2/qos/configuration/guide/fqos_c/qcflfi.html

[Michael Darr]

Thanks for responding, chrihussey.  The site is connected to an MPLS circuit.  VoIP traffic is passing from this MPLS connection to another site at the moment, using their PRI.

[Joseph W. Doherty]

What protocol on the bonded links, MLPPP or perhaps ATM inverted muxed?  (I've used both with MPLS clouds.)

If another site has a PRI, you have a considerable bandwidth imbalance between the two sites, correct?  If so, especially with VoIP, you probably need effective QoS policies (likely what Chris is thinking too - although with full T1s, you shouldn't need LFI).  Also with MPLS, if your have other sites, and a multipoint topology, you often need very exacting QoS or MPLS QoS support too.