Questions tagged [data-link-layer]

In the seven-layer OSI model of computer networking, the data link layer is layer 2. The data link layer is the protocol layer that transfers data between adjacent network nodes in a wide area network or between nodes on the same local area network segment.

From Wikipedia:

In the seven-layer OSI model of computer networking, the data link layer is layer 2; in the TCP/IP reference model, it is part of the link layer. The data link layer is the protocol layer that transfers data between adjacent network nodes in a wide area network or between nodes on the same local area network segment. The data link layer provides the functional and procedural means to transfer data between network entities and might provide the means to detect and possibly correct errors that may occur in the physical layer.

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Why do we need IP header checksum when CRC is already present at Data Link level?

If there is any corruption in the IP header then it will be detected by CRC at data link level of the next immediate router and the frame will be discarded. Why do we need the IP header checksum at all?
dewesh jha
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Why pcap_set_rfmon fails each time?

I'm working on a low level sniffer based on libpcap. Everything works perfectly but the assert with pcap_set_rfmon() fails each time. I don't think that I made any mistake to get this result. I post a little snippet of the main function. If you have…
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Is there an method to convert wifi frame to ethernet frame?

I've searched for some information about frame structure in wifi and ethernet in the Data Link layer and found out that the two frames look quite different. I am wondering if there is some method in the router that converts wifi frame to ethernet…
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Carrier Sense Multiple Access with Collision Detection and Ethernet

I had a doubt, CSMA/CD is used by Ethernet. Ethernet is end to end, ie connected between two nodes. I hope, It has different channel for transmission and reception. Then how could a collision occur. Can't understand, correct me if I am wrong.…
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Data link level transmission

At the link level, responses about receiving frames go from one node to another, or a node is waiting for a response from a router, this router from another router, etc.?
adxlf228
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Which is most used Error Control mechanism at DataLink Layer?

I had read 3 error control techniques i.e Stop and Wait ARQ, Go Back N ARQ and Selective ARQ All I wanted to know which technique is currently being used in networking industry... Can someone give me any links to get updated on current changes in…
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What is the Difference between REJECT and SELECTIVE REJECT in HDLC protocol?

I was reading about the HDLC (High-Level Data Link Control ) protocol in which the frame's control field has a 'Type bit'. The type Bit 1 is for REJECT which is basically a Negative Acknowledgement packet asking to retransmit the damaged frame. Now…
alex
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Visibility of IP addresses in layer 2?

Whether IP addresses will be visible to layer 2 (data link layer) devices. If not, then how come those layers use ARP protocols to convert IP address to MAC address without knowing IP address. Thank You.
Ahamed Yasir
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Ethernet frame size constraints (payload)

Designers of ethernet have maintained the MTU as 1500 bytes(for payload),i wish to know what is the reason for that? Because IP datagram size (allowed is much more than 1500 bytes) then why ethernet designers chose frame size smaller than IP…
supriya
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802.15.4 Link Layer 1-hop neighbors

I have been looking for information about 1-hop neighbors on link layer in specification of the protocol. Unfortunately I could not find the answer to my question. Has a node in 802.15.4 MAC protocol, information about its 1-hop(directly connected)…
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OMNET++: How to obtain frame's source MAC Address in INET 4.0?

I am using INET Framework 4.0 with OMNET++. I have customised my Ieee80211ScalarRadio module to read signal power and source MAC Address of the beacons received from various APs in my AdhocHost. Here is my custom CIeee80211ScalarRadio.ned…
Farzan Badakhshan
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RandomAccessFile opening file does not work

What I am doing is creating two nodes that will talk to each other through text files for example: Node 0 is neighbors with Node 1 and vice versa. Node 0 will open up text file from0to1.txt and Node 1 will open up a textfile from1to0.txt. I verify…
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medium limitations of datalink layers protocols?

When using a specific datalink layer technology, for example Ethernet, do we have limitations of the used medium (i.e. Ethernet). Can we use radio connections to connect two LANs over Ethernet?
Ahmad
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CRC-16 checksum is not matching for HDLC frames

I've a streaming HDLC data as follows: 00 CE DB B1 FB 94 BC 51 D8 87 CF FF FB FF FF FF FB FF FF F9 7E AE 79 3D C4 D6 7B DB BD 7E 7B DF B8 FE 7B D8 7A 0B 3D ED DD 5B 3D EC DF 17 FF FC FE F3 FF FF FD 7F FC BD BF 9D BC 6C FF 05 FE FD FF 33 FE 51 FE C3…
dibyendu
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How to access/read/write/program/listen in the first four layers of the OSI Model?

I am wondering how do all the networking dance components work: How can I program/read/write/access raw and parsed data in: the physical layer (through the NIC)? the data-link layer? (e.g. so as to make my own switching OS) the network layer? (e.g.…
Jonathan Ginsburg
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