OSI Model - Physical Layer Help

[Yodums]

For this group assignment my part is to find what protocols are used in this layer and what for. I don't know where to start. Google has alot of results but it is all over the place and I don't know what site is 'good.' Would anyone be able to clue me in on this?

I was able to get this so far from someone:

The physical layer is concerned with transmission of unstructured bit streams over a physical link such as a cable, it is responsible for the electrical and procedural characteristics to establish maintain and deactivate the physical link. Simply speaking it is the transmission method, i.e. wire, cable, radio waves, stream of light over a fiber optic line etc.

Yodums

 

[JasonKosi]

What that person told you is accurate. The physical layer is basically just that -- the physical cables, connectors and electro-magnetic pulses (radio waves) that carry the signal.

As far as which protocols are used in this layer -- that sounds like a trick question to me. Perhaps your instructor is referring to specifications and standards (Cat5, UTP/STP, RG6)?

 

[zoopa_man]

That is not a trick question !!! Read this carefully....it's a direct quote form my networking book from back in the days of pain and suffering at college...

My Network + guide to networks...Tamara Dean says this...

" The Physical layer is the lowest, or first, layer of the OSI Model. The layer contains the physical networking medium, such as cabliing, connectors, and repeaters. Protocols at the Physical layer generate and detect voltage so as to transmit and recieve signals carrying data. When you install a NIC in your desktop PC, you are establishing the foundation that allwos the computer to be networked. in other words, you are providing a Physical layer. The Physical layer sets the data transmission rage and monitors data error rates, though it does not provide error correction services. Physical network problems, such as severed wire, affect the Physical layer. Similary, if you instert a NIC but fail to seat it deeply enough in the computer;'s circiut board , your computer will experience network problems at teh Physical layer.

The IEEE has set standards for protocols used at the Physical layer. In particular, the IEEE 802 standards specify how data is handled by Ethernet and Token Ring networks. The terms "layer 1 protocols" and "Physical layer protocols" refer to the standards that dictate how the electrical signals are amplified and transmitted over the wire. "

 

[ucfswimmer]

zoopa_man is absolutely correct, the IEEE standrads are protocols that are used on the physical layer...like for example, 802.11b for the way data is sent wirelessly over the 2.4Ghz frequency range. good luck yodums.

~jeff~

 

[zoopa_man]

A few Physical layer protocols that will be important for you to know in class....


IEEE 802.2 The default frame type for Novell's intraNetware network operating ssytem. it suports the IPX/SPX protocol. the defining characteristics of it's data portion are the source and destination service access points tha belong to th logical link control layer, a sublayer of the data link layer.

IEEE 802.3 Ethernet The orgional NetWare Ethernet frame type and the default frame typpe for networks running NetWare versions lower than 3.12. It supports the only the IPX/SPX protocol. Ethernet 802.3 is sometimes called 803. "raw" because it's data portion contains no control bits.

IEEE 802.5 Token Ring

IEEE 802.12 100BaseVG (VG stands for Voice Grade)

 

[TC]

Physical layer protocols specify the media contention methods. Two common examples:

Ethernet (CSMA/CD)
Token Ring (token passing)

 

[Oswalden]

Hold on, are we talking the OSI model or the DOD model? If speaking the DOD then you are correct about the IEEE standards. If not, then the 802.xx are part of the Data Link Layer of OSI which organizes the data into the segments to be send via CSMA/CD (LLC sublayer) using MAC address (MAC sublayer) or other method. Physical is standards such as cat5e, rj45, ag-58. The key is to remember that the 7 layer OSI model isn't an actual protocol stack and therefore can be open to inturptiation, while the DOD model is the offical 4 layer structure to the TCP/IP suite.

 

[zoopa_man]

Oswalden your correct....the DOD model and OSI model are two separate things... we were taught in class that the first layer of the DOD model corrisponds to the data link, transport and physical layers of the OSI model. I remember the whole class having a hell of a time keeping all of this stuff streight in our heads...Sorry i didn't clarify more that CSMA/CD is a protocol for the physical layer and more spsfic protocols like the 802.xx fit more into the data link part of the OSI model then physical layer....so keep it simple in class and use CSMA/CD and token passing as examples of protocols....as soon as you get more spsfic it all goes to hell. lol I'm still juggling all this stuff in my head...A word to the wise keep your college books handy because it all turns to soup if you don't use it every day.

My networking teachers famous words "clear as mud"

 

[JasonKosi]

You forgot 802.11a, 802.11b and 802.11g wireless...

And then there's 802.1p and 802.1q which refer to QoS, packet scheduling, trunking and STP...

"Clear as mud" is sooooo accurate.