Difference between data link layer and network layer?

Question

can you help me out here...i dont want links.

Answer 1

Why 7 layers?
Why are there 7 layers in the stack? I thought that TCP/IP only had 5.

5. Application - DNS, HTTP, FTP, Telnet, etc.
4. Transport - TCP, UDP
3. Network - IP
2. LAN/Link - network address (physical or MAC)
1. Physical - low-level signal


—The preceding unsigned comment was added by 64.247.79.58 (talk • contribs) 03:48, 8 June 2003.

TCP is best looked at is 5 layers but some companies such as cisco try and shoehorn it into the OSI 7 layer model Plugwash 20:10, 22 September 2005 (UTC)
[edit]
Confusing layers
When I think about it, I think ICMP is on the same layer as those too .. IGMP I know nothing about, though. --Wikipedians/arcade

Yes, that's right: Even although ICMP is a required protocol for the TCP/IP stack, it is still implemented as a Transport layer protocol, not as a Network layer protocol. This can be easily seen by the fact that ICMP has a protocol number (it being protocol number 1). The same is true for IGMP (except that it has protocol number 2).
In fact, there is only one network layer protocol in the TCP/IP stack: IP itself. -- Wouter Verhelst 12:42, 9 February 2004
Hmm, when I think a bit more about it. The Internet Protocol Suite doesn't follow the OSI layering all the way, so the stack is quite simply ... wrong, as it is portrayed.

The 3 bottom layers are pretty okay. However, IMCP is dependent on IP, so it needs to be pushed higher up on the stack. HTTP/STMP/SNMP and so forth are _NOT_ dependent on the layer that is presented as beneath it, and thus needs to be bumped down.

Roughly, something like:

7. Protocols that are tunnelled through those in layer 6. Say an XML protocol served through a HTTP server.
6. HTTP/SMTP/SNMP/FTP/and-so-forth
5. TCP/UDP/ICMP/Whatever
4. Transport (IP, for the internet protocol)
3. Network
2. Data Link
1. Physical

Answer 2

It's all so much fictitious crap anyway, no one implements the OSI model exactly. In a nutshell the datalink layer is based on physical addressing and is usually bounded by a LAN. The network layer is logical addressing and crosses network boundaries (ie, subnets in the tcp/ip world).

Answer 3

http://en.wikipedia.org/wiki/OSI_model