Download SEECSNET ® Source Host Application Transport Network

A quick intro to networking
1. Framing
SEECSNET
2. Encoding
3. Error detection
4. Reliable delivery
5. Access Mediation
All nodes on SEECSNET implement and understand the
SEECSNET protocol consistently allowing any arbitrary node to
contact any other node.
However, a SEECSNET cannot access a node outside this network
The problem of internetworking:
how can a SEECSNET connect to any arbitrary node connected to
an arbitrary network (other than its own)?
Ethernet
SEECSNET
Token Ring
By using a router/ gateway having an
interface connected to each network.
The problem of flat addressing:
Even if we have a router, how does a SEECSNET node identify an
Ethernet node? (or, any other node on a different network)
Ethernet
SEECSNET
Destination
Token Ring
Source
We need a hierarchical address that can identify a host
while also identifying its network. This is the
commonly used IP address.
The problem of incompatible heterogeneity:
Even with a hierarchical address to identify a node on another
network, a SEECSNET node can only transmit using its own
packet/ addressing format.
Ethernet
SEECSNET
Destination
Token Ring
Source
Encapsulation and
Virtual addressing
[ class activity ]
How do we modify the SEECSNET packet to enable
internetworking using concepts of encapsulation and
virtual addressing
Design the frame format
SEECSNET IP
Higher-layer data
Class Activity
Problem: Even if we have a hierarchical address through which
we can identify a node on another network, for actual
transmission, SEECSNET node can only use its own format.
Ethernet
SEECSNET
Destination
Source
Token Ring
The router receives the SEECSNET frame and
removes the SEECSNET header to recover the IP
packet.
SEECSNET IP
Higher-layer data
Class Activity
Problem: Even if we have a hierarchical address through which
we can identify a node on another network, for actual
transmission, SEECSNET node can only use its own format.
Ethernet
SEECSNET
Destination
Source
Token Ring
The router forwards the IP packet on the
appropriate Ethernet interface after making a
routing decision and adding appropriate header.
Ethernet IP
Higher-layer data
Class Activity
Problem: While using IP address and MAC address has allowed
node to node communicate, how can we identify the end-to-end
communicating processes?
Ethernet
SEECSNET
Destination:
HTTP server
Source: HTTP
client
Token Ring
IP
SEECSNET IP SEECSNET
TRANSPORT
APP data
SEECSNET packet (sending)
SEECSNET IP
TRANSPORT
APP data
Application
Transport
HTTP message
Network
(application layer data)
Data Link
Bits
Source Host
SEECSNET packet (receiving)
SEECSNET IP
TRANSPORT
APP data
Application
Transport
HTTP message
Network
(application layer data)
Data Link
Bits
Destination Host
History of internetworking
SEECSNET IP
TRANSPORT
APP data
Internetworking functionality
TCP/IP initially had the following format (Cerf and Kahn, 74)
Local
header
Source
Dest.
Sequence
number
Byte
Count
Flag
Field
Text
Checksum
Vint Cerf
This functionality has now been broken down into two distinct layers
(IP is another protocol and TCP is another protocol)
Bob Kahn
Proposed TCP/IP as a
single integrated
protocol in 1974 for
internetworking
Chapter 1:
Computer Networks and
the Internet [K&R]
Chapter 2:
Direct Link Networks [P&D]
[ End of lecture ]