# TCP/IP

1. Internet: “network of networks” • Interconnected ISPs
2.Protocols define the format, order of messages sent and received among network entities, and actions taken on msg transmission, receipt.
3. protocols are everywhere
• control sending, receiving of messages
• e.g., HTTP (Web), streaming video, Skype, TCP, IP, WiFi, 4G, Ethernet
3. Internet standards
• RFC: Request for Comments
• IETF: Internet Engineering Task Force

## Internet Structure
### Network edge:
- hosts: clients and servers
- servers often in data centers
### Access networks, physical media:
- wired, wireless communication links
### Network core:
- interconnected routers
- network of networks


## Delays

## Delays & Queueing

## Traceroute
Traceroute program: provides delay measurement from source to router along end-end Internet path towards destination.

## Throughput


## Encapsulation
Encapsulation in TCP/IP is the process of adding headers and trailers around some data1234. The headers contain additional information about the data and are added by each layer of the TCP/IP model. The headers are used for exchanging control and status information about the progress of the communication. When data moves from upper layer to lower layer of TCP/IP protocol stack, during an outgoing transmission, each layer includes a bundle of relevant information called "header" along with the actual data.


Persistent vs Non-persistent


# Cache

# Email

# DNS

# Sockets