Questions tagged [layer1]

For questions about the OSI layer-1 (physical layer).

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4answers
201 views

Can we use two pairs of UTP with hubs?

I understand that hub always supports for half-duplex communication. In that case we should use one out of four UTP pairs. However, I read that for 10BaseT ethernet two pairs of UTP cables are used ...
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1answer
18 views

characteristics of different bit sequences over network

Do different sequences of bits exhibit different characteristics when sent over a network. For example, does one sequence of bits have a higher error rate than another sequence? If there are ...
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1answer
35 views

Is MIMO equivalent to link aggregation?

Is MIMO the wireless version of link aggregation in wired networks? I'm not asking if MIMO is a similar link aggregation protocol like LACP or PAgP, what I'm asking is if it is the same concept as ...
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0answers
12 views

Understanding OSI communication model from Electronics Perspective [duplicate]

I have gone through the OSI communication model and the associated levels. But I do not understand on how is this implemented in the Hardware level. Or let me put it like this. Suppose we have a USB ...
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2answers
2k views

PTP 1588 VS SyncE

I have been struggling a whole day to understand the real differences of Precise Time Protocol (IEEE 1588) and Synchronous Ethernet (syncE) and their role in the network. Greatly appreciated if you ...
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1answer
242 views

What is the purpose of twinax cables and how does it differ from straight through and cross over cables for the connection of unlike and like devices?

What is the purpose of Twinax cables and how does it differ from straight through and cross over cables for the connection of unlike and like devices? I want to know whether there is any difference ...
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2answers
23 views

How could the line rate of T1 be 1.544 Mbps?

T1 signal is the output of a 24-to-1 digital multiplexer whose inputs are 64 kbps each (plus one framing bit). But a multiplexer is simply an electronic device that selects between several inputs and ...
60
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9answers
20k views

Is 30 Mbit/s fibre faster than 30 Mbit/s copper? [duplicate]

A network engineer professional is overseeing our town's installation of fibre and was explaining how much faster it was. I pointed out that it wasn't a silver bullet as you had to pay the provider ...
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4answers
16k views

what is the difference between a CSU/DSU and a modem?

I'm so confused, both do the same function, converting the analog to digital, but what's the difference?
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2answers
370 views

What is the benefit of sending some data uncoded in a 10GBASE-T PHY frame?

For 10GBASE-T / IEEE 802.3ae the Physical Coding Sublayer is extended with a low-density parity-check (LDPC) code. IEEE 802.3™-2012 55.1.3.1 Physical Coding Sublayer (PCS): The 3259 bits are ...
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1answer
53 views

Questions regarding incoming packets at optical splitter from optical line terminator (OLT)

I am currently studying the textbook Computer Networking -- A Top-Down Approach (7th Edition) by Kurose and Ross. In a chapter on Home Access: DSL, Cable, FTTH, Dial-Up, and Satellite, the authors say ...
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3answers
23k views

Multiple POE over a single cable

I try to solve a problem using Power Over Ethernet technology to Power supply differents devices. I would like to avoid to buy new router and try to make it work without any expensive costs (if ...
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0answers
7 views

802.11 vs MACA protocol RTS/CTS [duplicate]

im in serious doubts about how diferent are the 802.11 and the MACA protocols I can´t find a simple explanation on the internet on how these are different when it comes to their RTS/CTS parts. Are ...
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3answers
160 views

What classifies as crossover cable?

The definitions I've read say that crossover cable is cabling which the receive and transmit pairs are swapped around. My question is based on the fact that beyond this, I've seen some diagrams which ...
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2answers
6k views

When is “grounding” a concern when running Cat6a cables?

I'm educating myself on how to terminate Cat 6a cables. I've seen some articles talk about "grounding" requirements because of the "shielding" in the cables. But is grounding a concern if I'm just ...
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4answers
127 views

does fiber optic transmit data as fast as light?

I dont know where to ask this question. So i think its best suited for networking community. As fiber optic transmit data using light. So we are getting/sending data at the speed of light ?? I did ...
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1answer
64 views

SFP to RJ45 for 10Gbit network

I am in the process of upgrading some of our network into 10Gb and grabbed the following: A network switch by netgear, mode:GS110EMX A bunch of assorted cat8 cables(for future proofing) Two 10gtek ...
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3answers
7k views

Fiber cable mixing single mode with multi mode

Does following scenario work? We have single mode fiber running between two building, but we have MMF patchcord connected to SPF (SFP-10GBase-SR). [SPF]---MMF----[=======SMF======]----MMF---[SPF] I ...
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2answers
2k views

Full Duplex and Collision Domain

I have a very basic query on Collision Domain and Full Duplex Mode. There are two types of logical topology: Ethernet and Token Ring . Whenever we read about Ethernet the first thing that we are ...
6
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2answers
441 views

How to properly name TIA-606-B Cabling Subsystem 1 far end identifier for work area equipment outlets?

We are moving to TIA-606-B for labeling. I have read most of the TIA-606-B standard. Some parts I have only skimmed, while others I have studied in depth. I do not understand the rationale behind the ...
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2answers
57 views

AOC cables for Brocade Fiberchannel

I have a FC switch from brocade with 16Gb ports and I want to connect to an array enclosure from another vendor. For internal requirements, it should be connected through twinax AOC cables. My problem ...
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2answers
82 views

SFP/SFP+: Extender? F/F panel passthrough?

My primary question is this: Is it possible to have a simple passive SFP/SFP+ bulkhead passthrough connector, with two female SFP/SFP+ sockets facing opposite directions and wired directly together, ...
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5answers
91k views

Cable Colors and Purpose

I've been doing some work with some big businesses and so far I've learned yellow is internet and blue is phone. Is this a standard or is this just a personal chose? Do colors mean different tasks?
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4answers
1k views

Can I run two separate internet connections over one Cat5e cable

I have two ISP's coming into the building. One is a T1 that is going to be used for VOIP phones. The second is high speed internet connection going to be used for internet. Each office has one cat5e ...
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1answer
52 views

Inital value for the scrambler in 10GBASE-R

The standard says "There is no requirement on the initial value for the scrambler. The scrambler is run continuously on all payload bits". I'm curious how the scrambled data can be recovered. To my ...
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6answers
3k views

Do network adapters read incoming bits in a single stream?

When a Gigabit network adapter is receiving data, how is it receiving the bits? Is it seeing it all in one stream of 0's and 1's? Or is there somehow multiple streams of 0's and 1's coming in at the ...
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2answers
107 views

Could long sequences of consecutive zeros cause Ethernet link problems?

I am in the process of debugging an Ethernet communication issue. Basically using Wireshark to monitor the source data the stream was intermittent when the cable was removed and subsequently ...
6
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8answers
6k views

What do the positive and negative (+/-) transmit and receive pins mean on Ethernet cables?

So I'm trying to understand the pin layout of an Ethernet port, specifically for 8P8C which to my understanding is the most common. Of the eight pins, only four are apparently used for communication, ...
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0answers
56 views

What are the differences between the Optical Carrier (OC) and Synchronous Transport Mode (STM) protocols, in regards to SONET/SDH?

I understand that OC-3c and STM-1 are technically consistent, and STM-1 can transport different quantities of CEPT-N signals, but why not just use OC-3c and forget STM altogether? Edit: Originally ...
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3answers
9k views

How is it possible to run VoIP on CAT3. Do you not need CAT5 for the voice data?

So I never knew this till today but I thought you needed CAT5 for VoIP but this business is running VoIP on CAT3. Don't you need the extra wires for the voice, data and power?
3
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3answers
629 views

Collision domain question

I'm studying for my CCENT exam, and not quite sure why the book (official Cisco) says that there are 5 collision domains in this example. Isn't it supposed to be 4? The hub on the left, the hub in the ...
2
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1answer
46 views

Reliable transfer but unreliable auto-negotiation?

I have two servers, the first with a built-in and add-on 10gbit port, and the second with built-in gbit and add-on 10gbit (Syba AQC107), communicating through a feed-through rated for gigabit ...
4
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2answers
11k views

RJ45 Cable only has 4 wires

The cable that connects to my rj45 only has 4 cables, blue, orange, blue stripe, orange stripe. When I connect them to their corresponding ports, there is no internet connection.(Blue = 4, Orange = 6, ...
14
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5answers
5k views

How exactly does an Ethernet collision happen in the cable, since nodes use different circuits for Tx and Rx?

I am trying to understand how a collision occurs in Ethernet, especially when a duplex mismatch exists or when on a legacy Ethernet network two nodes transmit simultaneously. Everyone explains the ...
3
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3answers
3k views

Cabling standard for Layer-3 switch

I want to know the appropriate cable type between: Layer-2 and Layer-3 switch Layer-3 switch and router Is it cross-over or straight through?
2
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1answer
227 views

Using an Ethernet cable and USB Ethernet adapter at the same time?

What would happen on using an Ethernet cable connected to one network and then plugging in another Ethernet cable but using an USB Ethernet adapter from a different network. Would it connect to both ...
2
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2answers
322 views

How to extend CAT6 ethernet 2m from ceiling down to server rack?

Previously, we had a 6RU comms cabinet near the ceiling. We've now replaced this with a full-depth server rack sitting on the ground. The plan was to remove the old patch panel, and punch it down ...
2
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3answers
3k views

What is the maximum distance for blowing optical cable through pipes?

What is the maximum distance for blowing optical fiber cable with compressed air through pipes? The method known also as Cable jetting. Taking into consideration no lubricant is used. I am asking ...
4
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1answer
979 views

NEXT Crosstalk calculation

The NEXT value for a given cable type is generally expressed in decibels per feet or decibels per 1000 feet. NEXT value varies with the frequency of transmission. The higher the NEXT value, the ...
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3answers
174 views

The recommended settings for giga ethernet connected to Ethernet port

What is the recommended duplex and speed configuration for giga ethernet port connected to legacy ethernet (10 mbps) port and there is no available duplex command available on the ethernet side? If ...
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1answer
213 views

Does the PHY signal interframe gap to the MAC?

I'm trying to decode an Ethernet II frame with type instead of length indication. Theoretically this should be done by receiving and storing the data between start of frame and interframe gap. However ...
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2answers
167 views

Cat6A Junction Boxes in the US

I'm looking around the internet and can't seem to find a Cat6A junction box available in the US. Is there a reason they aren't sold in the US? Basically, I have a Cat6A cable that is run to the wrong ...
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1answer
153 views

Cat 6 life expectancy [closed]

how long will cat 6 cable survive outside if it is not an external grade cable. No sunlight touches the cable but only cold temperatures of around -10c, everyday every year. the cable has no holes, ...
2
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1answer
137 views

T-568A/B on the same cable

I'm helping my friend punch down all of the Cat5-e cable in his office. Some of it went to existing patch panel and some went directly into a switch. There are two patch panels, each was about half ...
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8answers
2k views

Using sound waves in layer 1

Is it possible, in theory, to use sound waves as the physical medium to transmit data over a network? In other words, could you implement layer 1 of the OSI networking model using sound waves or am ...
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1answer
91 views

Velocity(factor) of different cable types - Collision domain

I need to calculate the max length of a collision domain. There is this formula. In short: maxLength = (c * velocityFactor * 512 Bit)/(vBit) c = speed of light velocity factor = ? vBit = bit ...
2
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4answers
543 views

What is the difference between Ethernet types, considering bandwidth?

Different types of Ethernet (standard Ethernet, Fast Ethernet, Gigabit Ethernet) have different speed of data transfer (10 Mbit, 100 Mbit, 1 Gbit). Why is that? On the physical layer, the speed of ...
1
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1answer
63 views

Which layer and protocol takes care of power-down and power-up of ethernet port

Which layer and protocol takes care of power-down and power-up of ethernet port (based on cable connected or disconnected) in a Linux machine. I think it (power-up and power-down) will be taken care ...
4
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2answers
169 views

Noticeable limitations or penalties from using inline fiber couplers

Is there any noticeable limitations or penalties from using inline fiber couplers, such as those in a patch panel to join multiple fiber runs together? Currently I have switches joined together ...
0
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1answer
142 views

How 1gbe works in full duplex? [duplicate]

1gb Ethernet works in full duplex and the maximum theoretical throughput is 2Gbps. Every pair gives 250 mbps in both directions. How it can work in full duplex on the one pair?

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