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18 votes
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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 "...
jcbermu's user avatar
  • 4,497
11 votes
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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 ...
Zac67's user avatar
  • 84.8k
10 votes

Why use PPPoE and not use IP directly?

A few reasons. Firstly that is just the way it has always been and ISPs are loath to change a working setup. Secondly it's possible to create translators between different types of PPP. Just because ...
Peter Green's user avatar
  • 13.3k
9 votes
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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 ...
Zac67's user avatar
  • 84.8k
9 votes

Why use PPPoE and not use IP directly?

Yes, the "E" in PPPoE stands for ethernet. The PPP stands for Point-to-Point Protocol. PPPoE and PPPoA are often used with DSL. PPP was the original protocol which was allowed by the DSL Forum. PPP ...
Ron Maupin's user avatar
  • 99.8k
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 ...
Mike Pennington's user avatar
8 votes
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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 ...
Zac67's user avatar
  • 84.8k
7 votes
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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-...
Ron Maupin's user avatar
  • 99.8k
6 votes
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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 ...
Martin Rosenau's user avatar
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 ...
Zac67's user avatar
  • 84.8k
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 ...
Anas Programmer's user avatar
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 ...
Ron Trunk's user avatar
  • 67.6k
5 votes
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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. ...
Zac67's user avatar
  • 84.8k
4 votes
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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 ...
Maverick's user avatar
  • 1,412
4 votes
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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 ...
Ron Maupin's user avatar
  • 99.8k
4 votes
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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 ...
Zac67's user avatar
  • 84.8k
3 votes
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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 ...
Zac67's user avatar
  • 84.8k
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 ...
Eden Akhavi's user avatar
3 votes
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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 ...
Zac67's user avatar
  • 84.8k
3 votes
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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-)...
Zac67's user avatar
  • 84.8k
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 ...
Kit's user avatar
  • 101
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 ...
Zac67's user avatar
  • 84.8k
3 votes
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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 ...
Peter Green's user avatar
  • 13.3k
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 ...
Peter Green's user avatar
  • 13.3k
2 votes

In Fiber Optic Telephone line, how light signals are converted to the voice signals?

In case of telephone broadband, voice signals travels through the telephone line. At the user premise, the modem coverts the voice signals into digital information. A dialup modem converts between ...
Peter Green's user avatar
  • 13.3k
2 votes

In Fiber Optic Telephone line, how light signals are converted to the voice signals?

I'll answer your heading question: There are two ways that voice can be carried over fiber lines: analog and digital. In an analog system, voice can be carried over a fiber line by modulating an LED ...
ruhnet's user avatar
  • 121

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