TCP/IP question

[Yohhan]

Question regarding TCP/IP -- As I understand it, Ethernet provides no acknowledgement, while the Transport layer in TCP/IP provides end-to-end acknowledgements using sliding window cumulative ack. What about the IP? It can provide datagram and virtual circuit services, correct? Is IP using some sort of an acknowledgement when using a virtual circuit? I'm trying to tie everything together...

 

[cmetz]

IP does not provide any sort of virtual circuit. That's TCP, or SCTP, or an application on top of UDP. IP simply moves a chunk of bits to its destination address and IP-level protocol.

 

[Yohhan]

So it does not make use of any sort of acknowledgement then? It just sends information and doesn't care if it makes it to the destination?

 

[randal]

IP is not connection oriented. It is Layer 2, and leaves all connection, or transmission things to L3 and above -- like TCP: Transmission Control Protocol. L2 IP just provides ... transit. EG, how to get from point A to point B. It never actually ensures that things get anywhere, it just provides routes, or pathways, for some other protocol to get from place to place. Whether this other protocol cares about data integrity (TCP) or not (UDP) is up to it, not the IP layer.

Think of it like the NYC rail system. The tracks are laid out all over the place, physically connected to each other (Layer 1). At junction points, you have train stations (routers) that know where things are supposed to go via their Train Station Number (IP). The tracks do not move things, they just provide the paths. The stations do not do anything besides let you know where you are and how to get to where you're going. It is the train that is responsible for making sure that connections (Layer 3) get made, with pathway information from the Stations (L2), running on the metal rails (L1) so that things actually do move from place to place. It is the job of the stuff inside the trains (peope) to actually do something upon arrival (L4+)

Not the best analogy ever, but hopefully it helps.

 

[cmetz]

Yohhan, correct.

 

[ScottMac]

Uh, ALMOST correct ...

Ethernet is layer two, IP is layer three, TCP/UDP is Layer four ...

(As a side note: Netbeui / NETBIOS can do session-oriented / connection-oriented communication at layer two. )

FWIW

Scott

 

[bgroff]

Well, technically its Ethernet with LLC2 at layer 2. Netbeui is still a higher level protocol in the grand scheme of things. It just can't be routed...

Originally posted by: ScottMac
Uh, ALMOST correct ...

Ethernet is layer two, IP is layer three, TCP/UDP is Layer four ...

(As a side note: Netbeui / NETBIOS can do session-oriented / connection-oriented communication at layer two. )

FWIW

Scott

 

[Yohhan]

So, NetBeui takes care of addressing with MAC addresses then right?