Here is the early morning edition....dateline dining room table....11pm on an otherwise quiet Monday evening. 24 has just ended and the adrenaline is pumping. No better time to tackle the ins and outs of the OSI model. It should be easy. The layers themselves are a no brainer. Its the danged protocols and sub-layers that are getting to me. I know that the physical layer is on the wire. The layer that handles the voltage. The top most layer, the application layer is another easy one. Its the one closest to the user. HTTP, SNMP, SMTP, and the such. The presentation layer, another easy one, NO protocols just services. JPG, TIFF, etc..... Session layer, application to application traffic cop. RPC, and SQL play there. So far so good. Transport layer, the computer to computer traffic cop. Now the protocols get a little fuzzy but I found a way around that. The T in transport leads me to TCP which helps me with UDP. TCP is a connection oriented protocol so the logic stands good there. Now onto the Network layer. And I seem to hit a wall right here. Data Link layer...same thing. I know that the data link layer has the sub layer of MAC and one other LLD, I think. But I draw a blank on the protocols for the network and data link layers. I know there is ICMP, IP, IGMP, and the like and I am pretty sure its the network layer for that. What I can't do is provide the details on just WHAT the network layer provides. I can stretch and say that the data link layer provides the LAN/WAN translation and that it draws me to FDDI, etc...you know, the protocols associated with LAN/WAN traffic. But still no confident statement.
These are the struggles I am having. My practice tests are coming along and with less than 2 weeks they better be. This is a stumbling block that I HAVE to get past. Even if there is not ONE question on this exam about the layers, yeah right, I MUST get this down.
Maybe some divine intervention would help.
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