Layer 2 flow control?

[pastrin]

Hello, I am enjoing very much this 7th edition of the CCNA Study Guide. Lot of bang per buck.

Please, can you explain shortly how the Data Link layer protocols do the flow control (page 23). I always assumed that the flow control is done at Transport layer (i.e. TCP protocol)

Thansk,

Patrick

[Big Evil]

The uppermost sublayer is Logical Link Control (LLC). This sublayer multiplexes protocols running atop the Data Link Layer, and optionally provides flow control, acknowledgment, and error notification. The LLC provides addressing and control of the data link. It specifies which mechanisms are to be used for addressing stations over the transmission medium and for controlling the data exchanged between the originator and recipient machines.

Transport Layer protocols, for example TCP, but not UDP, provide end-to-end reliable communication, i.e. error recovery by means of error detecting code and automatic repeat request (ARQ) protocol. The ARQ protocol also provides flow control, which may be combined with congestion avoidance.

HTH.

[lammle]

To continue on with BE's thoughts, the LLC layer is used in Wireless communication today for managment.
It is not used in Ethernet transmission.
Token Ring, AppleTalk, and a few others used it for management, but Ethernet pretty much sucks, so there is no managment.
Wireless absolutely needs it.
Also PPP uses it for NCP to identify the routed protocols.
Todd

[pastrin]

Thanks both of you for your fast answer.

At the moment I don´t see it very clear, but I will work a bit more through the book and maybe I will come back to this question (hope not).