## Posts Tagged ‘F2R001A’

### COAP

Thursday, November 15th, 2012

In the following exercise, we are going to study the CoAP protocol (Constraint Application Protocol ) used in Wireless Sensor Network (WSN), to simplify implementation in Sensor Nodes which have very limited resources in term of memory, computing power and energy. The standard is generic and does not make any assumption on Layer 2, but in our case we will suppose that layer 1 and 2 are IEEE 802.15.4. At layer 3, the 6LoWPAN protocol compresses the 40 bytes of the IPv6 header into 20 bytes. Another characteristic of WSN, is the high error rate on the radio link which leads to frame losses.

Monday, September 3rd, 2012

Good book for the class: OPEN SYSTEMS NETWORKING: TCP/IP AND OSI, David M. Piscitello A. Lyman Chapin,  Addison-Wesley Professional Computingk, 1993

### RES1 Connection vs datagram (12/12)

Thursday, October 27th, 2011

Finally we have a look on the Connection Oriented mode and the Datagram, se the main differences in term of Quality of Service. When also visit the famous hour glass model for IP or how the OSI RM can be reviewed by IETF.

### RES1 Network Layer (11/12)

Thursday, October 27th, 2011

## Network Layer

We look in more detail and at layer 3, why it is good to cut the information in little pieces called packets. We study French geography and why packets offer a better multiplexing and good performances.

### RES1 HDLC Framing (10/12)

Thursday, October 27th, 2011

We study the framing, how we divided a continuous flow of information into limited size PDUs and the meaning of all HDLC fields.

### RES1 Data Link Layer (9/12)

Thursday, October 27th, 2011

## Data Link Layer

The exercises shown that Send and Wait protocol does not offer good performances when propagation delay is long compared to transmission time. In that case it is better to send several unacknowledged frames instead of waiting for acknowledgments before sending another frame. We study HDLC protocol which can be view as the ancestor of all other anticipation protocols. There is an error in the slides. Instead of  an attentive reader will have noticed that the exact formulae is $\sum_{i=0}^{\infty} i.x^i=\frac{x}{(1-x)^2}$. But the result is correct.

### RES1 Send and Wait (8/12)

Thursday, October 27th, 2011

Data Link Layer

Now we have all the element to build our first protocol called Send and Wait. We will try to formalize its description to make it look like a real standard. We use Finite State Machine to describe its behavior.

### RES1 CRC (7/12)

Thursday, October 27th, 2011

## Data Link Layer (2)

Then we go really into the communication world. We see how we can detect a transmission error using CRC and that a frame with a wrong CRC will be discarded.

### RES1 Omelet protocol (6/12)

Thursday, October 27th, 2011

## Data Link Layer

We will wend more time on the Data Link layer, since here we can illustrate the protocol behaviors and detail all the elements.

First we start empirically to build a stupid protocol used be a cook to send an omelet recipe to a student. We will see that the basic hypothesis (negatively acknowledge when a problem occurs) is not good.

### RES1 Physical layer (5/12)

Thursday, October 27th, 2011

## Physical layer

Even if we don’t focus too much on the physical layer, we see the property we expect from the physical layer (such as clock synchronization) and some way to code binary information.