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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
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9 votes
Accepted

Is QoS an issue for VOIP calls over the Internet? If not, why not?

VoIP over the public Internet can be a problem, but it usually works good enough, most of the time, although there can be times where it sucks. Most ISPs have extra cost features where they will honor ...
Ron Maupin's user avatar
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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

Is QoS an issue for VOIP calls over the Internet? If not, why not?

I'm trying to decide whether I should buy SIP trunks from my ISP or a 3rd-party. and... Is QoS an issue for VOIP calls over the Internet? Short answer: End-to-end QoS is NOT offered on the public ...
Mike Pennington's user avatar
7 votes

How are different phone/GSM operators connected with each other?

As simply as possible, telephone calls are routed across a network of switches which are interconnected using trunks. There are interconnect points for different operators/carriers' switches. Since ...
Krackout's user avatar
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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
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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 do we need ATM if SONET/SDH can carry IP directly?

SONET is a physical layer protocol (layer-1). You need a datalink layer protocol (layer-2) to handle framing. That was originally ATM, because that was one of the dominant L2's used by carrier ...
Ricky's user avatar
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4 votes
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How are different phone/GSM operators connected with each other?

There is the Public Switched Telephone Network (PSTN) that connects calls between wired (fixed line) and wireless telephony subscribers (GSM is just the 2nd generation wireless telephony system, and ...
auspicious99's user avatar
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 ...
Zac67's user avatar
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3 votes
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Phone and PC network sharing one wifi bridge

It will work. Keep in mind this to learn why: 1 - A LAN is a single broadcast domain and single collision domain. Collision Domain: It means that a collision will be sensed by all the devices in the ...
jcbermu's user avatar
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3 votes
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How are PBX extensions configured and how are outside lines obtained?

First of all, does a PBX require its own power supply? A PBX does require it's own power, and you must have batteries or a UPS in the event of a power outage. If your PBX is Centrex (hosted at the ...
Ron Maupin's user avatar
  • 100k
3 votes

How could the line rate of T1 be 1.544 Mbps?

A T1 is 8000 frames per second. Each frame is 193 bits: a frame bit, followed by 24 8bit channels. 8000 * (1 + 8 * 24) gives a line rate of 1,544,000. Remember, the T1 was designed for voice ...
Ricky's user avatar
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3 votes

Why does SONET need atomic clock but T-carrier does not?

SONET, or rather the synchronous digital hierarchy it's running on, requires very tight clock coupling across the whole structure. In order to stay within the sub-millisecond tolerances, there's no ...
Zac67's user avatar
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3 votes
Accepted

Do telephone calls work at Layer2?

First of all, as already said, the only thing in common between mobile networks and Wi-Fi is that it is wireless. Besides that, these are completely different technologies with completely different ...
Effie's user avatar
  • 1,818
2 votes

Smart switching calls in a company phone calls

Typically in order to handle this type of scenario, you need to add an ACD (Automatic Call Distribution) component to your telephony solution, and tie it into your CRM. The idea is that your CRM tool ...
Jeremy Gibbons's user avatar
2 votes

How are PBX extensions configured and how are outside lines obtained?

A PBX is typically implemented in organizations that have many users who each require a telephone. They typically dial one another via 4 digit dialing. If a PBX phone user wants to call and order a ...
Ronnie Royston's user avatar
2 votes
Accepted

Can cat6 be used as a 1:1 replacement for telephone cable?

A higher category cable can be used for a lower category cable. Ordinary telephone cable is Category-3 cable. The downside is that simply replacing one category cable for another can be very ...
Ron Maupin's user avatar
  • 100k
2 votes

Working of a analog telephone - Basics

the audio signal has a bandwidth of 20 Hz to 20 Khz. Humans have a hearing range of somewhere around that, though it varies between individuals. But you don't need to pass anything like that range ...
Peter Green's user avatar
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2 votes

Forward single DID number to sip trunk

I have a solution working with a Cisco 2800 acting as a Session Border Controller (CUBE) in front of an Asterisk box. The inbound patterns and outbound patterns don't overlap (for me) so its a matter ...
Mike Tubby's user avatar
2 votes

How to terminate the 3 pairs coming from 66 block into suite for POTS line

Two things you should do: Pick up the line that is currently working and run ANI (Automatic Number Identification) on it. At the time of this writing, you can do ANI in North America by calling 1-800-...
Todd Wilcox's user avatar
  • 1,135
2 votes

Can you nest Private Branch Exchanges?

Yes, that is possible - the local telephone exchange is basically just a large PBX (without the P/Private bit). Depending on your PABX, you may not even require multiple layers of trunk access code ...
Benjamin Dale's user avatar
2 votes

Wiring question at POTS DEMARC point

I would say it is some type of electrical grease, to keep moisture out. Maybe try trace the pair from the block you are wanting to connect into, trace that pair back to the cable coming into the ...
ViperX's user avatar
  • 66
2 votes

Ip telephone being not served by DHCP

Assuming your Call Server is 10.0.20.3, then I think you've got a mistake in your configuration - you're referencing the TFTP Server IP address using boot-file instead of boot-server. Try the ...
Benjamin Dale's user avatar
2 votes

Is SONET a physical layer or a data link layer?

SONET defines a physical layer (or variants thereof) and a common data link layer, similar to Ethernet. (Circuit-switching) SONET used to be a popular carrier technology but has largely been replaced ...
Zac67's user avatar
  • 85.8k
2 votes

Is ATM a Wide Area Network?

ATM is a layer-2 protocol. Yes, it is (was?) mostly used in WAN deployments. However, there were PCI network cards to add ATM links to a PC/server. (3com 3c975, comes to mind) When you purchase a ...
Ricky's user avatar
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2 votes
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PRI and BRI cards

A Basic Rate Interface (BRI) provides two data channels while a Primary Rate Interface (PRI) provides 30 channels. While ISDN phones use BRI interfaces, PRI interfaces are used for trunks toward the ...
Zac67's user avatar
  • 85.8k
2 votes

Do telephone calls work at Layer2?

IP phone or VoIP is an application - accordingly located in the application layer (OSI L7) - off-topic here. If IP is used, you've got the classic network stack L7 - L4 - L3 - L2 - L1, where each ...
Zac67's user avatar
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