Another issue with DSL bonding is crosstalk, which is pretty bad in many cases of telco wiring.
10 years ago there was a huge amount of surplus Cisco 1700s with SHDSL line cards (apparently coming from Czech government's project to connect every school to internet in early 00's) and we had huge spool of flat phone cable that was left over from earlier project. So we had the bright idea to wrap ethernet trafic in AAL5, pass that over SHDSL and use that as an LAN for anime convention. Interesting observation from that it matters whether the cable is coiled or un-coiled. We built and tested the whole network in a lab (with coiled cables), it worked well, the G.991bis bonded links synced up at 6Mbps with two pairs and everything was good. We labeled everything and we built the exact same thing (including same cables) at the venue and the links will not go above 1.5Mbps and were frequently losing sync. Disabling the second bonded pair caused it to work reliably at 2Mbps. (Back then, we did not need that much of bandwidth, it was essentially for few SCCP phones, some IP tunelled serial ports and ssh)
Well, next year we bought two boxes of Cat5 cable and switched to native ethernet (and today the backbone spans are 10G fiber, as it also carries video streams).
Ah yeah, if it was just flat cable instead of twisted pair or coax, coiling the cable could have made a massive difference in the characteristics. Interesting that coiling worked better...
10 years ago there was a huge amount of surplus Cisco 1700s with SHDSL line cards (apparently coming from Czech government's project to connect every school to internet in early 00's) and we had huge spool of flat phone cable that was left over from earlier project. So we had the bright idea to wrap ethernet trafic in AAL5, pass that over SHDSL and use that as an LAN for anime convention. Interesting observation from that it matters whether the cable is coiled or un-coiled. We built and tested the whole network in a lab (with coiled cables), it worked well, the G.991bis bonded links synced up at 6Mbps with two pairs and everything was good. We labeled everything and we built the exact same thing (including same cables) at the venue and the links will not go above 1.5Mbps and were frequently losing sync. Disabling the second bonded pair caused it to work reliably at 2Mbps. (Back then, we did not need that much of bandwidth, it was essentially for few SCCP phones, some IP tunelled serial ports and ssh)
Well, next year we bought two boxes of Cat5 cable and switched to native ethernet (and today the backbone spans are 10G fiber, as it also carries video streams).