## Local Server
There are several reserved IP address ranges that will never be used for normal network assignments. One of these is the range from **127.0.0.0 to 127.255.255.255**, which is reserved for loopback addressed on the local machine. The loopback component indicates that the external network will not able to access these IP ranges.

On all operating systems, 127.0.0.1 will always direct to your current host. In addition, localhost is a hostname that directs to 127.0.0.1.
## Observing Packets


* Each listed network interface represents a piece of software or hardware that connects to a public or private network. For example, the *Ethernet0* interface listed is the default network card used to communicate over the INternet for this particular VM.


* We know that TCP initiates an upfront connection and acknowledges when packets have been received. This initial negotiation is known as a three-way handshake, and has three parts:
1. One side sends a packet with a *SYN* flag.
2. The other side responds with *SYN* and *ACK* flags.
3. The first side sends an *ACK* flag.

* None of the packets we have examined so far contain any data. We can determine this by looking at the *len* meber:


* Looking at all the packets, we can see that the only packets with data have the PSH flag. This flag tells the TCP connection to immediately send whatever data is inside the packet to the associated application instead of placing it in a buffer. We can filter for this flag in Wireshark to only see the packets that we care about via *tcp.flags.push == 1*.

## Packet Structure
* When we select a packet in Wireshark, it display the full packet broken down in different segments.


* Given that data in packets is often compressed, it is difficult to determine the purpose of a single packet in isolation. Instead, it is easier to look at the overall flow of network traffic and determine the role of each packet. In our case, the flow of network traffic for connection looks like:


* Priciple:
1. Client -> Server Packet 1
2. Server -> Client
3. Client -> Server Packet 2
4. Server -> Client
5. Client -> Server Packet 3