1. Slides taken from: Computer Networking by Kurose and Ross
Networks
Slides taken from: Computer Networking by Kurose and Ross

2. What’s the Internet
millions of connected computing devices: hosts, end-systems
pc's workstations, servers
PDA's phones, toasters
running network apps
communication links
fiber, copper, radio, satellite
routers: forward packets (chunks) of data thru network

3. What’s the Internet protocols: control sending, receiving of msgs
e.g., TCP, IP, HTTP, FTP, PPP
Internet: "network of networks"
loosely hierarchical
Internet standards
RFC: Request for comments
IETF: Internet Engineering Task Force

4. What’s Protocol human protocols:
"what's the time?"
"I have a question"
introductions
... specific msgs sent ... specific actions taken when msgs received, or other events
network protocols:
machines rather than humans
all communication activity in Internet governed by protocols
protocols define format, order of msgs sent and received among network entities, and actions taken on msg transmission, receipt

5. Protocols

6. Network edge end systems (hosts): client/server model
run application programs
e.g., WWW,
at "edge of network"
client/server model
client host requests, receives service from server
e.g., WWW client (browser)/ server; client/server

7. Connection-orientated Service
Goal: data transfer between end sys.
handshaking: setup (prepare for) data transfer ahead of time
Hello, hello back human protocol
set up "state" in two communicating hosts
TCP - Transmission Control Protocol
Internet's connection-oriented service
TCP service [RFC 793]
reliable, in-order byte-stream data transfer
loss: acknowledgements and retransmissions
flow control:
won't sender overwhelm receiver
congestion control:
senders "slow down sending rate" when network congested

8. Network Core mesh of interconnected routers
the fundamental question: how is data transferred through net?
circuit switching: dedicated circuit per call: telephone net
packet-switching: data sent thru net in discrete "chunks"

9. Packet Switching
To improve the efficiency of transferring information over a shared communication line, messages are divided into fixed-sized, numbered packets
Network devices called routers are used to direct packets between networks
Messages sent by packet switching

10. Protocol Layers Networks are made of many "pieces": Question: hosts
routers
links of various media
applications
protocols
hardware, software
Question:
Is there any hope of organizing structure of network?

11. Organization of air travel

12. Organization of air travel: a different view

13. Protocol Stack application: supporting network applications
ftp, smtp, http, telnet
transport: host-host data transfer
tcp, udp
network: routing of datagrams from source to destination
ip, routing protocols
link: data transfer between neighboring network elements
ppp, ethernet
physical: bits "on the wire"

14. Protocol Layering and Data
Each layer takes data from above
adds header information to create new data unit
passes new data unit to layer below

15. Data Message

16. In Class Assignment Use telnet to connect to your CSCI account
Open a DOS command prompt window and type:
telnet candler.cs.unca.edu
Login to your CS account:
Your login name is
<first-6-characters-of-last-name><First-initial><Second-initial>
Your password is
<the four letters "csci"><last four digits of student id>
Use the yppasswd command to change your password.
Use FTP to transfer a file to your CSCI account
Use your favorite editor (e.g., wordpad, notepad, word) to create a file---the contents of the file don’t matter.
Store the file in the directory c:\files; create that directory if necessary.
Follow these directions to transfer that file via FTP to your CSCI directory.