18
votes
Accepted
What is SNR Margin and Line Attenuation?
The SNR margin is the Signal to Noise Ratio margin.
Signal to Noise Ratio is the relation between the data signal level and the noise level.
Even the most perfect cable absorbs some noise. This "...
- 4,497
11
votes
Accepted
Why is the Ethernet Connection Symmetric?
The very first Ethernet standards were designed for using a single, shared coax wire. There's no benefit in making the connection asymmetric in any way.
Additionally, network nodes are generally ...
- 88.1k
9
votes
Accepted
does the DSL distance really add more latency
Twisted pair cable used for the local loop has a velocity factor of about .58 - each km of cable takes ca. 6 µs to travel, adding ca. 12 µs to latency. The rest of the Internet probably uses fiber ...
- 88.1k
9
votes
Why is the Ethernet Connection Symmetric?
Q: Why is ethernet symmetric (when compared to ADSL's asymmetry).
A: This is best explained by looking the technical reason for ADSL's asymmetry.
Quoting directly from wikipedia:
There are both ...
- 30k
8
votes
Accepted
ISDN and DSL comparison
You can't really compare those two technologies.
ISDN is a network protocol encompassing practically the whole OSI model from physical to application layer.
xDSL is a family of physical-layer line ...
- 88.1k
7
votes
Accepted
PPPoE interface doesn't use ARP
PPP doesn't use MAC addresses or ARP the way ethernet does, so no, there will not be ARP in PPP, but there may be ARP in the ethernet which carries the PPP frames. You will not see anything ethernet-...
- 101k
6
votes
Accepted
What are the reasons for ADSL to use ATM instead of Ethernet
According to the German Wikipedia the bit rates used in the time when ADSL was invented was the reason:
At that time the backbones of the telephone and internet providers operated at 1-40 MBit/s ...
- 2,356
6
votes
Is it possible to set up a DSL lab environment?
If I have a switch or laptop running a PPPOE server, could I go from ethernet-to-modem then connect the modem's WAN port to another modem's WAN port and have it connect via PPPOE?
No. A DSL modem is ...
- 88.1k
5
votes
What exactly is the local loop?
What is Local Loop?
The portion of the telephone system that connects your home or office to the nearest central office (CO) of your local telco.
The wiring used in the local loop is usually ...
- 331
5
votes
Why is the Ethernet Connection Symmetric?
Ethernet is a local area network technology, and it was designed with no assumption that traffic will be higher in one direction than the other.
It was developed long before the web or Internet was ...
- 68k
5
votes
Accepted
VDSL2 Cross Talk
They are just all mixed together.
No, they're not. Each pair must be kept together at all times; if you separate or recombine the single wires crosstalk goes through the roof and all is lost.
...
- 88.1k
4
votes
Accepted
What's the difference of TR-069 and Point-To-Point protocol?
I think you are confused with the terms Point to Point and TR-069 here.
An ISP normally uses IPOE/PPPOE/PPPOA for establishing the connectivity between CPE(Modem/Gateway) and their BRAS. They also ...
- 1,412
4
votes
Accepted
Can a VDSL2 to Ethernet converter be used as a replacement for a bridging VDSL2 modem?
The particular device you have listed is required to be used as a pair. This is for someone who want to extend a network across voice cabling, or for a small ISP to use to connect to customers. It ...
- 101k
4
votes
Accepted
Best way to replace DSL cable by CAT6 cable
The DSL line runs for hundreds or even thousands of meters on plain telephone cable (Cat-3ish). A few meters of Cat-6 will change nothing to improve signal integrity.
Just use any pair. Don't ...
- 88.1k
3
votes
What are the reasons for ADSL to use ATM instead of Ethernet
When ADSL came up in the late 1990s, Carrier Ethernet was in the far future - Ethernet was just 100 Mbit/s back then.
Then, carrier networks were SDH and used ATM as base protocol. This has changed ...
- 88.1k
3
votes
Accepted
What exactly is the local loop?
The local loop is your home's or business's dedicated connection to the nearest concentrator (often within a Point of Presence (PoP)). The concentrator basically multiplexes many connections to a ...
- 88.1k
3
votes
Accepted
Different SNR Margins for Downstream and Upstream
ADSL uses frequency-division multiplexing for transmitting and receiving, so the frequencies in either direction are quite different. The upstream uses lower frequencies, so very often it is less ...
- 88.1k
3
votes
Accepted
Establishing ip network over intercom
It depends on what the "intercom network" looks like. For something POTS or even ISDN-compatible you could use a pair of VDSL(2) modems with integrated splitters, most often called (Ethernet-over-)...
- 88.1k
3
votes
Why does a Spanish internet modem/router not require a DSL filter?
You only need to filter the connection to the telephone, the connection to the DSL router is not filtered.
The UK filter you show is just a splitter with a filter built in on the telephone side of ...
- 41
3
votes
Why Business Class router don't usually include ADSL?
A DSL or DOCSIS modem is a specialized bridging device.
Including one in a router is either a cheap gimmick or increases the expense of a business device that will limit its adoption.
Spring for the ...
- 101
3
votes
Why use PPPoE and not use IP directly?
As other answer, DHCP doesn't provide authentication. Any user can set static IP for his device. With PPPoE (and family), only authorized users can access the network.
3
votes
Accepted
Easier for Tx = Rx speeds with fiber than with DOCSIS or DSL?
Yes.
In general both DSL and Cable use "frequency division duplex" techniques. Consumer fibre services tend to use "wavelength division duplex". Professional fibre services often ...
- 13.8k
2
votes
How does DSL synchonization actually work?
The standards for the vaious variants of DSL are maintained by the ITU, https://www.itu.int/ITU-T/worksem/asna/presentations/Session_6/asna_0604_s6_p4_palm.pdf lists the standard numbers for the ...
- 13.8k
2
votes
Which kind of connection do i need for BGP peering?
You can bring up a BGP session (though you will likely have to override the default TTL limit), the problem is actually sending the data.
"next hop IP address" is a local concept, used to look up the ...
- 13.8k
2
votes
Accepted
Why Business Class router don't usually include ADSL?
Because "business class" implies use in many situations where the service may be supplied by something other than ADSL. Combined router/modems are pretty much a home/consumer niche device.
Getting ...
- 2,746
2
votes
does the DSL distance really add more latency
You won't get better than about 14ms ping time between France and Algeria due to the speed of light.
Lagency (ping time) is additive. If your ping to your gateway is 38ms, then even if latency ...
- 326
2
votes
How to avoid cable crosstalk?
While it doesn't hurt to keep cables apart a bit you don't need to.
The ADSL links likely run for hundreds of meters in parallel outside the building anyway. It's essential to keep the pairs intact ...
- 88.1k
2
votes
Pros and Cons of two different ISP connection Model
Whether you have a separate modem comes down to a few factors, and performance is very unlikely to be one of them.
Separate units are easier to maintain if you have to change one for any reason
But ...
- 16.4k
Only top scored, non community-wiki answers of a minimum length are eligible