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Pair Bond Question

Are both lines in a pair bonded setup used in parallel? Meaning one bit is sent down one line and the other bit in sent down the other. Or are they used in serial in which the system fills one line up and then uses the second one?

I'm just curious to know.
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Tom
Tom's Tech Blog

I am not sure I completely understand the question, but if the question is what I think it is, I believe it is in serial from what I have seen in the field

I have (rarely) seen pair bonded setups (both with the Pace/2Wire iNID as well as the Moto NVG589) that are actually in sync on both pairs as bonded pairs should be, but for whatever reason the DSLAM/VRAD does not seem to properly load balance the pairs.

For example, on a 25 Mbps pair bonded profile, each pair is in sync @ about 12.5 Mbps. I have seen trouble cases where the service dies once you ask for 3 HD streams. Why? The only thing I could come up with was once you ask for stream 3, you are asking for more than 13 Mbps, and if the pairs are not Load Balanced, pretty much the whole service dies. The solution pretty much involves getting new VRAD ports provisioned -- once new ports are assigned, it reprovisions with a proper load balance and the issue is fixed

But since the problem only occurs when asking for HD stream 3 (1 HD stream works fine; 2 HD streams get a little pixeled), that leads me to think it uses all the capacity of one pair before using the 2nd pair.

How does it work when you upgrade from a single pair to a bonded pair like when you upgrade to the Power Tier?
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Tom
Tom's Tech Blog

I am guessing that it's in parallel and not in serial -- the reason being is folks have mentioned that they have had line 2 go down and their service still worked (just slower). If the system "worked" in serial -- you'd have no service if one of the lines went down (I think).

From what I've read, it actually distributes data across the pairs per packet. Each pair is load balanced at Layer 2. Obviously, that per packet distribution only occurs dynamically when the 2nd VDSL connection negotiates and bonds.
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Scott, CCIE #14618 Routing & Switching
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