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Standard User Andrue
(knowledge is power) Mon 25-Mar-13 13:32:32
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21cn - how do packets get from ISP to customer?


[link to this post]
 
From what I remember Be's network was like a WAN and it consisted of switches that used MAC addresses to route packets. You could see this in a traceroute as an additional hop between your router and the first 'real' node.

Is 21cn routing using a lower-level protocol?

---
Andrue Cope
Brackley, UK

Just because he could. RIP.
Administrator MrSaffron
(staff) Mon 25-Mar-13 13:34:46
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Re: 21cn - how do packets get from ISP to customer?


[re: Andrue] [link to this post]
 
21CN is an IP based network, so uses IP based routing

Of course IP traffic can be tunnelled so you do not see the physical IP layer

Andrew Ferguson, andrew@thinkbroadband.com
www.thinkbroadband.com - formerly known as ADSLguide.org.uk
The author of the above post is a thinkbroadband staff member. It may not constitute an official statement on behalf of thinkbroadband.
Standard User RobertoS
(sensei) Mon 25-Mar-13 18:32:21
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Re: 21cn - how do packets get from ISP to customer?


[re: Andrue] [link to this post]
 
ISP >> WBC node >> WBC cloud >> exchange MSAN >> customer.

Plusnet have connections to three nodes.
Entanet to all twenty.

My broadband basic info/help site - www.robertos.me.uk | Domains,website and mail hosting - Tsohost.
Connection - Plusnet UnLim Fibre (FTTC). Sync ~ 54.2/15.2Mbps @ 600m. - BQM

"Where talent is a dwarf, self-esteem is a giant." - Jean-Antoine Petit-Senn.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Allergy information: This post was manufactured in an environment where nuts are present. It may include traces of understatement, litotes and humour.


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Standard User yarwell
(sensei) Mon 25-Mar-13 20:43:49
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Re: 21cn - how do packets get from ISP to customer?


[re: Andrue] [link to this post]
 
L2TP to the ISP isn't it ? In the early days you could see a load of BT IP's before your traffic got to the ISP, then with larger centrals and L2TP the first IP address was at your ISP even on 20CN.

--

Phil

MaxDSL - goes as fast as it can and doesn't read the line checker first.

MaxDSL diagnostics
Standard User jchamier
(knowledge is power) Mon 25-Mar-13 22:35:45
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Re: 21cn - how do packets get from ISP to customer?


[re: Andrue] [link to this post]
 
In reply to a post by Andrue:
Is 21cn routing using a lower-level protocol?

You won't see the 21cn network between you and the ISP as your traffic is encapsulated inside a PPP packet until it gets to the ISP's termination router. This is an L2TP connection from the 21CN network to the ISPs termination router as Phil mentions.

Unlike BE, and Sky's LLU where you see a router for your local exchange in the traceroutes, the PPP encapsulation hides all this.

James BT Infinity 2 19/09/2012 - Speeds ~46 / ~8.5 Mbps - Sync 48.9 / 10 Mbps @ 470m
Huawei modem -> Draytek 2820 -> Airport Extreme -> Switch -> Windows/Mac/Linux/NAS/Phone/TV
13 years of broadband - 1999 ntl:(512k/1M)/BTbusiness(2M)/Metronet(2M)/Bulldog(8M/16M)/BE(19M/16M)/BT FTTC(46M)
Standard User Andrue
(knowledge is power) Tue 26-Mar-13 07:32:25
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Re: 21cn - how do packets get from ISP to customer?


[re: Andrue] [link to this post]
 
Thanks for all the replies, folks. Helps fill in a little gap in my understanding smile

---
Andrue Cope
Brackley, UK

Just because he could. RIP.
Standard User chris6273
(committed) Tue 26-Mar-13 18:33:54
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Re: 21cn - how do packets get from ISP to customer?


[re: jchamier] [link to this post]
 
In reply to a post by jchamier:
In reply to a post by Andrue:
Is 21cn routing using a lower-level protocol?

You won't see the 21cn network between you and the ISP as your traffic is encapsulated inside a PPP packet until it gets to the ISP's termination router. This is an L2TP connection from the 21CN network to the ISPs termination router as Phil mentions.

Unlike BE, and Sky's LLU where you see a router for your local exchange in the traceroutes, the PPP encapsulation hides all this.


I don't think that is entirely correct; I've been having latency issues recently every evening with BT Retail and the problem is occurring on the 4th hop:

C:\Users\Chris>tracert bbc.co.uk
Tracing route to bbc.co.uk [212.58.253.67]
over a maximum of 30 hops:
1 <1 ms <1 ms <1 ms edge1-r-0-0-1.evansnet.co.uk [10.5.14.254]
2 8 ms 8 ms 7 ms 217.32.141.2
3 9 ms 10 ms 8 ms 217.32.140.206
4 141 ms 145 ms 146 ms 217.41.216.154
5 13 ms 13 ms 13 ms 31.55.164.75
6 14 ms 13 ms 13 ms 31.55.164.107
7 150 ms 151 ms 153 ms acc1-10GigE-0-3-0-1.bm.21cn-ipp.bt.net [109.159.
248.112]

The strange part is, the BT Wholesale Speedtest shows my ping as being very high so unless the BT Wholesale Speedtest server is located on BT Retail's network (Which wouldn't make sense as it's Wholesales' Speedtest platform), the Wholesale 21CN network must be visible in Tracerts like the one above and the ISP's network must begin somewhere after the 4th hop.

Got me wondering now I've read this thread because the encapsulation method is how I thought it used to work.

If this is wrong does anyone know why the Speedtest would churn out my high ping when its supposed to be in the 21CN Network?

-------------------------------------------------------------------
My Broadband Speed Test

Downstream Upstream
Connection Speed: 22494 kbps 1211 kbps
Line Attenuation: 16.0 db 9.7 db
Noise Margin: 2.6 db 6.7 db

Telewest (2004-2006): 256Kbps -> 512Kbps
BT (2006 - Present): 8128/448Kbps on 20CN Alcatel DSLAM -> 22494/1211Kbps on 21CN Huawei MSAN
Administrator MrSaffron
(staff) Tue 26-Mar-13 18:51:36
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Re: 21cn - how do packets get from ISP to customer?


[re: chris6273] [link to this post]
 
BT Retail is a different beast as they utilise the WBC network and also use some BT Wholesale resources for connecting to the Internet

Andrew Ferguson, andrew@thinkbroadband.com
www.thinkbroadband.com - formerly known as ADSLguide.org.uk
The author of the above post is a thinkbroadband staff member. It may not constitute an official statement on behalf of thinkbroadband.
Standard User chris6273
(committed) Tue 26-Mar-13 19:11:44
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Re: 21cn - how do packets get from ISP to customer?


[re: MrSaffron] [link to this post]
 
In reply to a post by MrSaffron:
BT Retail is a different beast as they utilise the WBC network and also use some BT Wholesale resources for connecting to the Internet


Aha makes sense.

-------------------------------------------------------------------
My Broadband Speed Test

Downstream Upstream
Connection Speed: 22494 kbps 1211 kbps
Line Attenuation: 16.0 db 9.7 db
Noise Margin: 2.6 db 6.7 db

Telewest (2004-2006): 256Kbps -> 512Kbps
BT (2006 - Present): 8128/448Kbps on 20CN Alcatel DSLAM -> 22494/1211Kbps on 21CN Huawei MSAN
Standard User yarwell
(sensei) Wed 27-Mar-13 08:41:33
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Re: 21cn - how do packets get from ISP to customer?


[re: chris6273] [link to this post]
 
so unless the BT Wholesale Speedtest server is located on BT Retail's network
The BT speedtest is accessed via your ISP unless your router connected with a speedtest specific domain instead, so it will go via BT Retail or other ISP unless you've done that.

--

Phil

MaxDSL - goes as fast as it can and doesn't read the line checker first.

MaxDSL diagnostics
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