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Author Topic: Whatever happened to 50 : 1 contention etc?  (Read 6424 times)

kitz

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Re: Whatever happened to 50 : 1 contention etc?
« Reply #15 on: September 02, 2016, 12:20:52 PM »

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I don't recall having any issues with either Tiscali or Bulldog back in antiquity.

Both were known to have major issues - worse than IPStream providers. 
Bulldog in particular was very badly hit because they were selling 2Mbps using 2Mbps datastream VPs.
The Bulldog forums at one time were in chaos after they started selling cheap datastream.  :(

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The equivalent modern-day pipes must have got a whole lot fatter than the 4 Mbps and 10 Mbps pipes shown in Kitz's 20CN diagram at
    http://www.kitz.co.uk/adsl/equip.htm

Yep that was 20CN. MiSP had/has ATM backhauls which meant 155/622Mbps. :/
21CN is here. Uses SDH on the backhauls so 10/100 Gbps pipes.  WDM will also be in use at the FTTx head-end exchanges which means greater capacity per fibre cable.

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Are today’s FTTP, FTTC, and ADSL users still seeing time-of-day related congestion?

You do occasionally still see hot S-VLANs, but its easier for BTw to spot and usually much quicker to resolve than with the old ATM (20CN) VPs. 
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Chrysalis

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Re: Whatever happened to 50 : 1 contention etc?
« Reply #16 on: September 02, 2016, 03:25:52 PM »

I think bulldog LLU was fine, but their datastream was a very different story.

Those days was the heyday for LLU providers as they bypassed the high BTw costs.
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kitz

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Re: Whatever happened to 50 : 1 contention etc?
« Reply #17 on: September 02, 2016, 03:52:00 PM »

Yes their datastream was very bad.   

LLU didnt come along until a few years later and coincided with the introduction of OFCOMs Broadband Access Market Classification.
OFCOM ensured that BTw had their prices fixed and BT couldnt reduce pricing until the exchange was de-regulated.   This ensured that LLU could undercut BTw by being able to offer cheaper broadband and force competition into the market. 
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Chrysalis

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Re: Whatever happened to 50 : 1 contention etc?
« Reply #18 on: September 02, 2016, 08:46:02 PM »

I made some comments in the past about sky's capacity.  This video its explained and given an idea just how much spare capacity they have e.g. their 8 primary routers individually could handle peak traffic load alone so if e.g. 7 failed there still would be no congestion.  Likewise the core network if half of it went down, there still would be no congestion.

https://youtu.be/uQUoO4Wb7s4?t=6m50s

The weakness is the daisy chaining of exchanges, as ignition pointed out on ispreview, those not on exchanges directly linked to POPs (thankfully not me) are at risk of outages if any part of the daisy chaining links fail.
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niemand

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Re: Whatever happened to 50 : 1 contention etc?
« Reply #19 on: September 05, 2016, 02:05:51 AM »

I suspect people would be very surprised if they knew how small exchange backhauls were in the ADSL days, and even now how small SVLANs are.

I am not aware of any exchanges that had VPs of 155Mb. 34Mb or less was normal and usually okay.

Even now a 1Gb SVLAN is a rarity and 100Gb doesn't exist as exchange backhaul. Many are on a few gigabit Ethernet links port channelled or load balanced via OSPF at most.

One case that comes to mind is where a 300Mb AAISP customer couldn't get above 200-220Mb. His FTTP had more bandwidth than the SVLAN that backhauls it.

Average usage is still only a megabit or two per connection at peak times.
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WWWombat

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Re: Whatever happened to 50 : 1 contention etc?
« Reply #20 on: September 05, 2016, 03:28:08 PM »

e.g. their 8 primary routers individually could handle peak traffic load alone so if e.g. 7 failed there still would be no congestion. 

Are you basing that on the presentation's statement that "Biggest P-router capacity ~= Total Traffic Served"?

Tim does say that, through dimensioning, that it just so happens that the capacity of a single P-router matches the total traffic being served.

However, Tim doesn't go on to claim that the network would still work congestion-free if 7 of the 8 P-routers failed. Instead, he only claims that the network would still handle "peak traffic" (evening) congestion-free if they lost one core site (ie 2 P-routers, one on each ring) or a major fibre route (which I assume to mean a route between 2 core sites, affecting both rings).

Given the architecture (dual-parented PoPs), I reckon that a loss of 7 of the 8 P-routers would immediately lose /all/ service to half of the exchanges, possibly three-quarters, depending on internal details. Being "congestion-free" would be the least of the problems then...
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Chrysalis

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Re: Whatever happened to 50 : 1 contention etc?
« Reply #21 on: September 05, 2016, 03:55:38 PM »

I didnt say it wouldnt go down, I just said peak time load was under 1/8 of the capacity of the p-router.
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tommy45

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Re: Whatever happened to 50 : 1 contention etc?
« Reply #22 on: September 06, 2016, 05:09:13 AM »

I don't recall having any issues with either Tiscali or Bulldog back in antiquity.

I'm pretty sure if the data cap were low I'd have breached it and would have never forgotten about it due to the subsequent beating  :lol:

Back then we had an old USB Tiscali modem and I used to have to run a 10m phone extension cable out the window if I wanted to use the internet in my room. Come to think of it I only had a laptop back then.... If only I knew routers existed  :o the folly of youth.
Tiscali Shudder Shudder,I joined them back in 2006 iirc, on their upto 2mbps product, and that was never throttled,even P2P torrents, then they re graded everyone to their 8mbps MAX product, that was heavily contended almost 12hrs every weekday ,and virtually all day at weekends, throughput was reduced to sub 1mbps levels dial up was faster, and that usb modem speed touch ST330 iirc  was terrible, as was their CS and Tech support , and the 0871 number you had to use to call them, needless to say i started researching my next ISP Ukonline a switch i did not regret,
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WWWombat

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Re: Whatever happened to 50 : 1 contention etc?
« Reply #23 on: September 06, 2016, 11:17:47 AM »

I didnt say it wouldnt go down, I just said peak time load was under 1/8 of the capacity of the p-router.

You weren't saying that either ... and I'd have left that simple statement unchallenged. (*)

Instead, you were making pronouncements about how congestion-free the network would be in the event of certain (huge) failure modes ... which aren't claims that Sky themselves make. Sky's claims are much more limited.

Capacity of one router is meaningless if it isn't fully populated to make use of the capacity. Nor if the core fibre routes can't handle that volume. Nor if there isn't a working router at the other end to receive that data and send it somewhere.

Network capacity is oh so different from router capacity. Network congestion is different from router congestion.

(*) - Perhaps even the simple statement is unlikely to still be true.

When Sky installed the new routers, the fact that the router capacity matched total traffic was happenstance: the hardware was new, with plenty of room for growth. As volumes grow (40%CAGR or more?), that happenstance disappears ... And was always likely to be rendered an obsolete observation.

Now, 18 months on, total traffic may well have doubled (judging from the estimates in the graphs earlier in the presentation). The observation likely no longer applies. It was a red herring, and never useful.
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Chrysalis

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Re: Whatever happened to 50 : 1 contention etc?
« Reply #24 on: September 06, 2016, 04:28:11 PM »

wombat if you want to twist my words into something that suits your agenda then go ahead, I know what I said and meant.

Traffic has more than doubled since he was talking about that p-router capacity (early on in the video before he talked about what they did since then which has included multiple upgrades as well as switching to one vendor only).  But likewise the router itself has been upgraded with newer kit.

I see you took a dig at VM in another post today and at sky here, no digs at BT of course.  Where is the BT presentation for their network? or is it commercially sensitive as usual?
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kitz

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Re: Whatever happened to 50 : 1 contention etc?
« Reply #25 on: September 13, 2016, 11:44:15 AM »

Quote
I am not aware of any exchanges that had VPs of 155Mb. 34Mb or less was normal and usually okay.

Nope the VPs were much smaller.  155/622 was the size of the backhaul pipe which would be split into VPs of varying amounts of bandwidth.  Back in 2003ish a typical VP for a newly enabled exchange was just 4Mbps. Technically speaking they could put 400 x 512kb lines on a 4Mbps VP @ 50:1 or 160 x 512kb lines on a 20:1 VP.


RE BT v Sky network.  You cant compare..  they are different types of topology.   
Sky's is based mostly on a ring, whilst BT's is meshed.

Meshed allows more resiliency.  The info is out there about BTw's network and available to SP's via their login details.  You used to be able to bypass the login for some info if youre prepared to do some digging around which is how I got some of the stuff for the main site.  Now its all pretty much locked down unless you have a login.  Anything from the Tier 1 exchanges is quite well meshed. The CORE PoPs have a lot of resiliency, I don't think Ive ever heard of there being a problem with the actual Core.  BT's point of failure appears to be Telehouse ;)
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Chrysalis

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Re: Whatever happened to 50 : 1 contention etc?
« Reply #26 on: September 13, 2016, 09:40:14 PM »

Yeah I agree with kitz, it would be stupid if BT were employing 4mbit pipes as physical backhaul, it was software limited, why did they cap it?  The regulator made sure they couldnt give themselves free bandwidth to have an advantage over LLU operators.  Its all about protecting LLU with ofcom.
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