Transcript Session_3a__Foundations_of_Computer_Networksx

A quick intro to networking
FTP
HTTP
DNS
TFTP
…
…
TCP
UDP
Applications
UDP
TCP
Narrow Waist
IP
Data Link
NET1
NET2
…
NETn
Physical
The Hourglass Model
To understand networks, let’s design a LAN technology
(direct-link network) which we shall call SEECSNET
Shared Link
Node
Cloud
Our SEECSNET protocol should support standard Internet applications like HTTP
Aside: let’s see a typical HTTP interaction
http://www.cricinfo.com
URL
…
A Network Interface Card (NIC) is responsible for the
following direct-link networking tasks:
NIC of
Ethernet
How will a SEECSNET NIC work?
Let’s focus only on framing
(for now) to understand the
heterogeneity issues across
different direct-link networks
NIC of
SEECSNET
NIC’s Interface to
the network
Packet sw.: each packet is like a telegram
Control information:
whose purpose is to
facilitate delivery of data
Header
Contains actual data
to be transferred
between applications
Payload data
HTTP message
(application layer data)
What should SEECSNET protocol contain ?
In general, a lower layer
protocol must identify
the higher layer protocol
contained in the payload
SMTP message
(application layer data)
DNS message
(application layer data)
HTTP message
(application layer data)
This demultiplexing ID used to identify protocol at a higher layer is variously called
type, protocol, port, etc.
What should SEECSNET protocol contain ?
In general, a (inter)networking protocol must
contain address of both the source and destination
?
A protocol, by definition, is a consistent mode of operation
Class Activity
Design the SEECSNET protocol
SEECSNET Application-layer data
1. SEECSNET packet format
2. SEECSNET address format
[ Discussion on class activity ]
The frame format used by Ethernet protocol
Figure Credit: “Computer Networks: A Systems Approach” by Peterson and Davie
Chapter 1:
Computer Networks and
the Internet [K&R]
All the chapter in general
Section 1.4 (may be skipped/ skimmed for now)
Chapter 2:
Direct Link Networks [P&D]
[ End of lecture ]