How can I determine backhaul method

I am considering a move from BT Infinity to Zen FTTC.

Having read a number of threads here, there seems to be an advantage to having Zen's own backhaul vs BT Wholesale.... but my question is whether this is the same as "LLU"? My exchange (Totton) doesn't have LLU according to Samknows.com, so would this mean traversing BT Wholesale to reach Zen... or are the two unrelated?

By the way, my traceroute to echo.zen.co.uk at the moment is as follows:

Tracing route to echo.zen.co.uk [212.23.5.209]
over a maximum of 30 hops:

1 <1 ms <1 ms <1 ms 192.168.2.254
2 * * * Request timed out.
3 * 11 ms 10 ms 31.55.187.197
4 12 ms 12 ms 11 ms 31.55.187.236
5 11 ms 11 ms 11 ms 195.99.127.52
6 11 ms 11 ms 11 ms peer1-xe8-3-1.telehouse.ukcore.bt.net [213.121.193.109]
7 11 ms 12 ms 16 ms linx-1.zen.net.uk [195.66.224.158]
8 13 ms 13 ms 13 ms ge-2-0-0-0.cr1.th-lon.zen.net.uk [62.3.80.41]
9 26 ms 19 ms 16 ms ge-3-0-0-0.cr2.kp-leeds.zen.net.uk [62.3.80.77]
10 17 ms 17 ms 16 ms ge-3-1-0-0.cr1.kp-leeds.zen.net.uk [62.3.80.73]
11 18 ms 19 ms 18 ms ae2-0.dr1.mbr-roch.zen.net.uk [62.3.80.69]
12 18 ms 17 ms 17 ms saussure.zen.co.uk [212.23.5.209]

... and to bbc.co.uk (appears to be the default benchmark):

Tracing route to bbc.co.uk [212.58.246.104]
over a maximum of 30 hops:

1 <1 ms <1 ms <1 ms 192.168.2.254
2 * * * Request timed out.
3 * * 11 ms 31.55.187.193
4 11 ms 11 ms 10 ms 31.55.187.228
5 19 ms 14 ms 15 ms 195.99.127.0
6 12 ms 11 ms 11 ms core2-pos9-0.bletchley.ukcore.bt.net [194.72.31.141]
7 11 ms 11 ms 11 ms 194.74.65.42
8 * * * Request timed out.
9 14 ms 12 ms 13 ms ae0.er02.cwwtf.bbc.co.uk [132.185.254.90]
10 13 ms 13 ms 12 ms 132.185.255.165
11 12 ms 12 ms 12 ms fmt-vip133.cwwtf.bbc.co.uk [212.58.246.104]

... I'm hoping a move to Zen will improve on that.

In reply to a post by gb003162:

Having read a number of threads here, there seems to be an advantage to having Zen's own backhaul vs BT Wholesale.... but my question is whether this is the same as "LLU"? My exchange (Totton) doesn't have LLU according to Samknows.com, so would this mean traversing BT Wholesale to reach Zen... or are the two unrelated?

Its similar, but not exactly related. GEA (which is the product ISPs use to access FTTC circuits in a similar way to LLU) works on a parent and child relationship for exchanges. Ie one parent exchange may have multiple child exchanges. The parent exchange will give an ISP access to subscribers at the child exchanges. This means an ISP can service a larger area than just visiting one exchange.

I believe if LLU is listed as available, then Zen are definitely available for their own backhaul. If they are not listed, then you may be on a child exchange. Best way to find out is to contact them.

In reply to a post by gb003162:

... I'm hoping a move to Zen will improve on that.

What is wrong with that? 12ms to the final destination, 11ms of that being the first hop? Seems reasonable to me.

Thanks for the explanation, I will indeed contact them and ask directly if they can determine the likely path.

I noticed an example of a 5ms round trip from a Zen FTTC customer to bbc.co.uk, so although I appreciate I'm probably splitting hairs, I'm keen to understand any potential improvement for that first hop.

This is all rather a silly distinction. What matters is how much bandwidth is being paid for and how it's managed, not who it belongs to. It's just a matter of costs. Some ISPs will just buy less bandwidth in the interests of minimising costs and some have more and might charge a bit of a premium.

All ISPs will make some use of BTW bandwidth at some exchanges simply because they need to get to a point of presence. It's simply not economic for alternative providers of backhaul to have fibre presence at every exchange.

There there's a little issue of routing. Some backhaul networks will have shorter paths from some locations and worse in others, simply because that's the way the routing works. Networks are constantly being upgraded, the topology changed. It's even possible that the details of the route taken might change when you resync.

Then there are a load more issues over the peering and interconnect solutions. Some ISPs will have better performance for certain functions and sites simply because of where they interconnect, what peering arrangements they have, how content delivery networks are used and so on.

Whether or not ISP A is better than ISP B will depend on local circumstances, what services are being used and any number of other factors. Possibly the least important factor is who provides the backhaul.

Whether it's 5ms or not will depend on location and the details of how the routing works. I've just pinged www.bbc.co.uk from where I live (Maidenhead) and that gives a stable 8ms on BT Infinity 2.

One thing to notice is that ultimately geography wins out (just try pinging a known US or even Australian site). The typical refractive index of the core of monomodal fibre is about 1.62 meaning that light propagates through it at about 185,000 km per second. That sounds quite fast, but it means every 90km of fibre adds 1ms to ping times (as it's a there-and-back journey). Fibre also rarely runs in a nice straight line between source and destination, and every hop and switch adds its own bit of extra latency.

Generally what matters most is not the absolute value of the latency (within reason), but whether it is stable or not. Zen do have a good reputation for this, probably because they don't scrimp on network capacity.

nb. in the US, latency times on electronic trading is so critical that some providers of electronic trade exchanges have built data centres to host trader's servers with equal length LAN cabling in order to equalise latency at the data centre level. Conceivably gaming companies could also equalise WAN latency (by introducing artificial delays on shorter links). There have been proposals to do this as a basic network service.

Post deleted by MrSaffron

In reply to a post by TheEulerID:

You might find this thread informative. It's about how several ISPs (Zen included) suffered an increased latency spike in the evening on several consecutive days which appears to be down to a circuit issue on a BTW network. It tends to show there's no such thing as and ISP that doesn't use BTW backhaul for some locations.

That was a thread I started. As mentioned at the end of the thread, it was a failure of a BT Wholesale network link from a major network node in the Milton Keynes area that caused the remaining links to be overloaded. Once BT Wholesale identified and repaired the problem, the problem never returned. Zen customers on the Flitwick (SMFK) exchange moved on to the Zen backhaul network in October 2014.


There is no price difference in Zen's consumer broadband products between "Zen network" and "BT Wholesale" network customers, though I would expect lower prices and greater availability of leased line and other low contention / dedicated bandwidth services in areas with a nearby Zen point of presence.

I have experienced a small increase in latency to London based services by moving to the Zen network and there was a little initial instability, but my monitoring shows the Zen network is now stable and my connection experiences very low jitter. Anyone who wishes can compare the bandwidth monitoring in my signature with that in the linked thread.

Edited by MrSaffron (Mon 05-Jan-15 13:55:44)

Deleted link to clone site and proper link should have been

http://forums.thinkbroadband.com/zen/4270597-fttc-la...

Any way of knowing which other exchanges have Zen backhaul? I am awaiting FTTC on SMWLS Wilstead exchange, and I know that Zen have a PoP in Bedford, I'd be interested to know if my exchange would allow near direct connection to Zen as I have been a Zen customer for a few years now and am very satisfied and don't intend to move anywhere else.