72
votes
Is 30 Mbit/s fibre for WAN faster than 30 Mbit/s copper?
30 Mbit/s is the same speed, no matter if it runs over copper or fiber.
However, there are important link parameters other than link speed/pure bandwidth, so there may be differences. First, latency ...
- 88.1k
63
votes
Accepted
Is Ethernet port blinking really useful?
Yes, blinkenlights are your friends! The lights can be very helpful when diagnosing problems - especially when dealing with non-managed switches or remote diagnosis with unexperienced users.
Rule of ...
- 88.1k
31
votes
Accepted
Why does an Ethernet cable have four pairs?
10BASE-T saw first light as StarLAN that made use of the already existing twisted-pair category 3 telephone cabling (instead of the dedicated coax that 10BASE5/2 required). That multi-purpose cabling ...
- 88.1k
30
votes
Is Ethernet port blinking really useful?
My very first step in troubleshooting network issues is this:
"Are there winky-blinky lights?"
It's the network port equivalent of asking someone if their computer and/or monitor is actually ...
- 401
28
votes
Is 30 Mbit/s fibre for WAN faster than 30 Mbit/s copper?
30Mb/s is 30Mb/s, but ISPs usually sell you “up to 30Mb/s” because the speed of DSL technologies is highly dependent on the distance between your equipment and theirs.
With fibre, you are more ...
- 381
24
votes
Accepted
What is this thread-like material on this Cat6 U/UTP cable?
It is used to split the outer shielding away without needing to use a sharp object which could potentially damage the wires themselves. It is commonly called a ripcord.
Image taken from http://netx....
- 356
21
votes
Accepted
How does a packet get corrupted in a network?
Packets are long streams of binary numbers (zeros and ones).
The zeros and ones are usually changes of an electric signal, specifically voltage changes.
To simplify, suppose that 0 is 0 volts and 1 ...
- 4,497
21
votes
Accepted
How LAN works in video games if only one station is permitted to transmit?
Only one device is allowed to transmit at any given time. At any other given time, another device is allowed to transmit.
How can you have a conversation at a dinner table if only person can speak at ...
- 759
19
votes
Is 30 Mbit/s fibre for WAN faster than 30 Mbit/s copper?
You might consider pointing out to your "network engineering professional" that the propagation delay in copper is LESS that that of fiber (in most cases).
The difference between the two is ...
- 68k
18
votes
Is 30 Mbit/s fibre for WAN faster than 30 Mbit/s copper?
It doesn't appear that any one has explicitly addressed the reliability of transmissions over fiber vs copper.
It may be true that, for example, your router is throttled to 30 Mbps, but the ...
- 281
18
votes
How LAN works in video games if only one station is permitted to transmit?
Some LAN protocols, on some media, are half duplex. That means that only one host on a LAN can send a frame at any given time. The classic example of this is the original ethernet, but the modern ...
- 101k
17
votes
Accepted
What do the positive and negative (+/-) transmit and receive pins mean on Ethernet cables?
Twisted pair uses differential signaling - in a pair, one wire is always the negative/complimentary signal of the other. In the simplest example, Transmit+ > Transmit- (higher voltage level) means 1 ...
- 88.1k
16
votes
Accepted
How exactly does an Ethernet collision happen in the cable, since nodes use different circuits for Tx and Rx?
To understand this you need to understand the historical context.
Originally Ethernet used a shared coaxial cable. Only one device could successfully transmit on this at a time. If two devices ...
- 13.8k
15
votes
How exactly does an Ethernet collision happen in the cable, since nodes use different circuits for Tx and Rx?
A hub is really just a powered cable that repeats every signal it receives on one interface to all the other interfaces. If two devices transmit at the same time to the receive of the hub interfaces, ...
- 101k
14
votes
Accepted
The maximum length of CAT6 for intranet network?
Per the ANSI/TIA/EIA 568, Commercial Building Telecommunication Standard, UTP cabling is limited to 100 meters. That length assumes up to 90 meters of solid-core (better performance, but fragile) ...
- 101k
14
votes
What does the naming convention for Ethernet standards mean: 1000BASE-T, BASE-TX, BASE-SX, etc.? What is the meaning of the components of the name?
BASE indicates baseband signaling - there is no modulated carrier, the frequency starts near zero and extends to a certain cut-off frequency.
BROAD indicates broadband modulation - there is a wide ...
- 88.1k
14
votes
Do network adapters read incoming bits in a single stream?
That depends.
While many Ethernet PHYs transmit data in a purely serial fashion (e.g. 100BASE-TX, 1000BASE-SX, 10GBASE-SR), some split the data stream into multiple lanes that are transmitted in ...
- 88.1k
13
votes
Do network adapters read incoming bits in a single stream?
Let's ignore the Gigabit part for now, and focus on your "2 devices are sending at the same time" part for a bit.
On shared media, this can actually happen and be a problem. Most wireless ...
- 873
13
votes
12
votes
Is 30 Mbit/s fibre for WAN faster than 30 Mbit/s copper?
Copper (ADSL or VDSL) specifies a maximum peak speed whereas fiber specifies a maximum average speed. My glass fibre (FTTH) connection is artificially limited to 50 Mbit/s average. At the start of a ...
- 221
12
votes
Do network adapters read incoming bits in a single stream?
This particular case is a complex one.
Regarding 1000baseT.
First: when we say in general that two devices are transmitting at the same time, they are not normally actually sending bits at the same ...
- 16.4k
12
votes
Accepted
Does bridging add delay?
Hi and welcome to Network Engineering.
As for "delay" vs "latency":
The terms are not always used consistently. Some hints may be found here.
I think generally, the term latency is used when ...
- 8,876
11
votes
Accepted
Multiple POE over a single cable
I know this is an older question, hopefully you've solved it by now, but I wanted to toss in my two cents, for the benefit of future generations if nothing else.
First of all, yes, ethernet and PoE ...
- 126
11
votes
What does the naming convention for Ethernet standards mean: 1000BASE-T, BASE-TX, BASE-SX, etc.? What is the meaning of the components of the name?
The first number represents the speed.
If the next part is "BASE", then it is baseband. If it is "BROAD", then it is broadband. This is the original meaning of baseband/broadband, not the government ...
- 101k
11
votes
Accepted
Do layer 3 protocols use layer 2 protocols?
Layer 3 (mostly IP) generally relies on the underlying layer-2 network (mostly Ethernet or Wi-Fi) for delivery. Just like a layer-2 network uses layer-1 links to actually move the bits.
The ...
- 88.1k
11
votes
Accepted
RJ45 Cable only has 4 wires
Your cable is not a proper UTP network cable as defined by TIA/EIA 568. In fact, the pairs used by the 10Base-T (10 Mbps) and 100Base-TX (100 Mbps) ethernet are 1-2 and 3-6. The 1000Base-T (1 Gbps) ...
- 101k
11
votes
Is Ethernet port blinking really useful?
The patterns of blinking lights on a switch can give you a quick overview of network health.
I used to work at a medium-sized company of about 100 staff, 250 PCs, a dozen servers, and the main ...
11
votes
How exactly does an Ethernet collision happen in the cable, since nodes use different circuits for Tx and Rx?
Great question.
In full duplex, there is a dedicated channel for traffic from "left to right" and a dedicated channel from traffic from "right to left":
Therefore, in full duplex, collisions are ...
- 15.2k
11
votes
Accepted
Why can't we create a hierarchy of hubs?
To add to Ron's point - a hub (...or a number of hubs) basically models the behavior of the original Ethernet, which is to say basically a big piece of coaxial cable. If one station transmits, all ...
- 6,152
10
votes
Accepted
Why preamble is not considered a part of the Ethernet Header?
Adding to jonathanjo's answer:
Ethernet has components in both layers 1 (because it can run over different media) and 2 (because the frames are the same on the different media).
The Preamble, SoF ...
- 101k
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