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Questions tagged [layer1]

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

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2answers
28 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, ...
0
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1answer
33 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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0answers
33 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 ...
2
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1answer
42 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 ...
3
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3answers
485 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
103 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
102 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 ...
6
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8answers
4k 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, ...
13
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5answers
4k 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 ...
0
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1answer
130 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
75 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
68 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, ...
11
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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 ...
1
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1answer
51 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 ...
2
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4answers
384 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 ...
4
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2answers
167 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
62 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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1answer
47 views

Influence of a TAP

I want to use a passive TAP to sniff all the network (100 Mbps full duplex twisted pair). I have two interfaces for sniffing and only one pair for each direction. Will the TAP add any noise? Or if I ...
10
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2answers
2k views

Does bridging add delay?

If I use a bridge to perform traffic sniffing like man in the middle will the bridge add a delay? And what word should I use delay or latency?
6
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2answers
981 views

How does a router know the MTU of a network?

I've done several exercises where you're given the MTU of a net or subnet, but I wonder how routers know the MTU of the nets they're connected. I've learnt that in OSPF protocol this information is ...
0
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1answer
136 views

Is a fiber optic connection considered a “wired” connection?

https://en.wikipedia.org/wiki/IEEE_802.3 As Wikipedia says, 802.3 is for ..."wired Ethernet". How can I name copper and fiber networks in one word to describe 802.3 standard and to distinguish from ...
3
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2answers
5k 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, ...
4
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3answers
202 views

A reason why Ethernet has maximum cable length confuses me

The answer in this post suggests that it has two reasons. While the impedance characteristics of a transmission line become less favorable for high speed data as the line gets longer (resistance ...
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2answers
119 views

Practical limits of shielded Ethernet cable

If I run S/FTP Ethernet cable ran next to 120V conductors (inside 3/4" conduit) for about 70 ft. is there chance that I'll have a usable data connection? I'm fully aware that this is a terrible way to ...
1
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1answer
147 views

How to use“ Multimode SFP GLC SX MMD” in Cisco Catalyst 2960 S connected LAN and single mode OFC network

We have single mode OFC network and CAT 6 CAT5 LAN with ethernet and gigabit Ethernet switches and ordered for "GE SFP, LC CONNECTOR LX/LH TRANSCEIVER FOR SINGLE MODE FIBER OF CISCO CATALYST 2960 S" ...
3
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1answer
738 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 ...
4
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2answers
115 views

Does it work to use CAT6 cable between two CAT5 cables?

I have two Cat 5 cables pre-installed in the walls. I need to connect two rooms, in which each room has its own set of in-wall Cat 5 cables and a slots. Does it work to use a Cat 6 cable to connect ...
4
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4answers
1k views

Do layer 3 protocols use layer 2 protocols?

I saw the STP on layer 2. The guy that made the tutorial says at the end : Even though it seems that Layer 2 access layer solutions are slowly being replaced by blazing fast Layer 3 solutions. ...
1
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2answers
131 views

What can I infer about a network connection using a cable tester (if anything)

I have a NS-468 cable tester for testing cables. This works fine but if I connect just one end of a RJ45 cable to a network, I only get 4 lights. This seems reasonable as I suppose 4 pins are for ...
1
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1answer
63 views

Counting the Number of re-transmission for a single UDP packet transmission in IEEE 802.11?

I was working with a client-server project based on UDP and 802.11 as a link and physical layer. There, the client was trying to probe some packets in the wireless channel to gauge channel condition. ...
6
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1answer
415 views

Why is there a separate set of 10 Gigabit fiber-optic transmission standards for WANs/SONET?

So, I'm reviewing the different IEEE transmission standards for an exam, and I've noticed that for the 10GBASE-X standards, there's two different sets of fiber-optic standards, 10GBASE-xW and 10GBASE-...
19
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6answers
4k views

What is this thread-like material on this Cat6 U/UTP cable?

Does anyone know what this thread-like material to the right on the picture is? Does it have anything to do with grounding? It is a Cat6 U/UTP cable.
4
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3answers
2k views

How to debug L1 Auto negotiation issues?

One of our Linux hosts has started switching its gears recently. While checking the interface speed, I could see that the interface has switched down to 10Mbps. The NIC and Switch are capable of 1G ...
9
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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 ...
2
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1answer
228 views

Stacking Dell N3000 with and without stacking cable (distance)

First question here. I have a new scenario that I am not sure on how to achieve. I have a stack of two Dell N3024 switches (our core stack), that I need to add two more units to. However, these two ...
1
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1answer
506 views

What is physically different between 10base-t and 100base-t?

I would assume that the primary difference between 10base-t vs 100base-t is the speed of the clocks interpreting the electrical signal. In other words, if you ensure that a "bit" is transmitted in 1 ...
4
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1answer
111 views

40G QSFP+ to 4x10G SFP+ Cable

I need to buy a Direct attach 40G QSFP+ to 4x10G SFP+ Cable that may be used to connect two FPGA boards. I can find reasonably priced cables, however the cables are usually "branded". Is it important ...
2
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1answer
116 views

What type of Cat5e cable is this?

I am a fairly new networker and today I was terminating some cable at a gas station that is being built. The network cable that had been run from the gas pumps to the wiring closet confused the crap ...
0
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1answer
43 views

Unconnected cable in a switch

A cable plugged into a switch but unconnected on the other end, might lead to any problem in a "noisy" environment (industrial)? It's short, 50 cm, but there are motors, inverters, power supplies ...
0
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2answers
246 views

How to avoid cable crosstalk?

I have 4 ADSL UTP cables. How much distance do I need to leave between cables to avoid crosstalk?
0
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1answer
52 views

RJ45 console cable specs

I need longer RJ45 <-> RJ45 cables to connect my devices to a centralized management console. It's like 5 meters going go the next racks, at 9600 baud rate. Can I buy random/cheapest cable from ...
1
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1answer
80 views

Circuit switching. How is the data rate divided for each circuit in a link for FDM and TDM?

FDM allocates portions of bandwidth to each circuit in the link. According to the Nquist equation, this would propotionally divide the data rate among the circuits. Now with TDM time slots are ...
2
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4answers
103 views

What is a standard term that includes patch panels but is broader?

I work in network infrastructure documentation at a public university. In discussions with coworkers, I frequently need to refer to devices that connect cables end-to-end. These devices are usually ...
2
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2answers
99 views

Effect of large amount of bare ethernet pairs on network performance

I have a client who has been experiencing a significant amount of performance issues in regards to their telemarketing floor. On my initial assessment, I found that where the ethernet is punched down, ...
0
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1answer
76 views

How to show all data (bitstream with preamble, SFD) on Ubuntu with an Intel Ethernet Interface?

On my PC I have an Intel Ethernet Connection I217-LM with e1000e driver. If I receive packets in Wireshark or any libpcap based tool, the received ethernet frames start with Ethernet II frame and end ...
1
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1answer
61 views

How to tell if network cable is LSZH

I just bought a 305 meter Cat 6a S/FTP LSZH Solid network cable. The cable I received is a Deltaco TP-53 cable, but I cannot see anywhere that this cable is really LSZH (Low Smoke Zero Halogen). I ...
0
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1answer
65 views

How southern cross cable can transmit IP/ Ethernet signals keeping in mind the physical limitation of Ethernet cables?

The Optical fibre can transmit/receive any ethernet frames or packets faithfully for 5kms. However, the cables laid in the southern cross i.e. under the sea beds must be several miles long. The ...
1
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1answer
73 views

Can bad cabling affect the overall network?

TLDR: Can a handful of problematic lines negatively impact the performance of the network as a whole? ... or would any problems stop once it reaches the switch? Longer Version (background): A ...
3
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1answer
514 views

To shield between patch panel and switch or not?

All network cables run from the outlets to the server room. They run next to power cables so it was decided to shield them. In the server room, they are going to be connected to a patch panel which ...
0
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1answer
54 views

Fiber optic cable juniper ex4500

Noob 10G question. I have a juniper ex4500 10G switch and Qlogic 3242 10G card. I use twinax cables for servers within the rack and they work just fine. But, now we added a new office which has 2 ...