Review – The
Internet’s Protocol
Architecture
1
Introduction
Internet standards
 Layered protocol architecture
 TCP/IP protocol suite
 Internetworking

Protocols, Internetworking & the Internet
2
Standards/Standards Bodies

The Internet Society
– Internet Architecture Board (IAB)
 defines overall architecture of the Internet
 provides broad guidance for IETF
– Internet Engineering Steering Group (IESG)
 provides technical management of IETF and
the Internet standards process
– Internet Engineering Task Force (IETF)
 designs and develops Internet protocols
 charters standards working groups
 publishes RFCs, with approval of IESG
 Eight areas defined: General, Applications,
Internet, Operations & Management, Routing,
Security, Transport, User Services
Protocols, Internetworking & the Internet
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Internet RFC Process
Internet Draft
Proposed
Standard
Best Current
Practice
Experimental
Informational
Draft
Standard
Internet
Standard
Historic
Protocols, Internetworking & the Internet
4
Key Features of a Protocol (as
defined by standards)
Set of rules or conventions to
exchange blocks of formatted data
 Syntax: data format
 Semantics: control information
(coordination, error handling)
 Timing: order, speed matching,
sequencing
 Actions: what happens when an
event occurs

Protocols, Internetworking & the Internet
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Internet Protocol Stack
Layers (a.k.a. TCP/IP stack)
 Physical
Application
Access
 Internet
 Transport
 Application
Transport
 Network
Protocols, Internetworking & the Internet
or…
Network
Link
Physical
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TCP and UDP

TCP:
– connection-oriented, handshake required
– reliable packet delivery in sequence

UDP:
– connectionless (datagram), no handshake
– unreliable packet delivery
– packets may arrive out of sequence or
duplicated
Protocols, Internetworking & the Internet
7
TCP
Defined in RFC 793, RFC 1122
 Provides the Internet’s primary reliable
host-to-host delivery mechanism
 Services offered:

–
–
–
–
–
–
basic data transfer
reliability (reliable data transfer)
flow control
multiplexing/de-multiplexing (one-to-one)
connections (maintains state)
precedence and security
Chapter 3 TCP and IP
8
TCP Header
Chapter 3 TCP and IP
9
UDP
RFC 768
 Connectionless, unreliable
 Less overhead
 Simply adds port addressing to IP
 Checksum is optional

Chapter 3 TCP and IP
10
TCP Applications
user
agent
mail
server
SMTP
SMTP
mail
server
user
agent
SMTP
user
agent
mail
server
FTP
client
TCP control connection
port 21
TCP data connection
port 20
file transfer
FTP
server
user
agent
user
agent
PC running
Explorer
user
agent
Server
running
Apache Web
Server
email
Protocols, Internetworking & the Internet
Mac running
Navigator
Web browsing
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TCP/UDP Service Comparison
Service
TCP
UDP
Basic data transfer
Yes
Yes
Reliable data transfer
Yes
No
Flow control
Yes
No
Yes, one-to-one
Yes, many-to-one
Yes (state)
No
Congestion control
Yes
No
Delivery precedence/priority
Yes
No
Optional processing information
Yes
No
Multiplexing/de-multiplexing
Connection management
Protocols, Internetworking & the Internet
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IP Headers – IPv4
IP Version 4 Header
Protocols, Internetworking & the Internet
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IPv6
Increase IP address from 32 bits to
128 bits
 Accommodate variable QoS flow
information and packet handling
 Fixed size 40-octet header for
performance, followed by optional
extension headers
 Longer header but fewer fields (8 vs
12), so routers should have less
processing

Chapter 3 TCP and IP
14
IP Headers – IPv6
IP Version 6 Header
Protocols, Internetworking & the Internet
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IPv6 Header








Version: 6
Traffic class: e.g. DSCP (more later)
Flow label: identifies packets in a sequence
from a particular source to destination that
need special handling (more later)
Payload length: total length of packet in
octets, minus 40 octets (max 65535)
Next header: specifies how to interpret
next field following the header
Hop limit: max number of hops for this
packet, decremented field, discard at 0
Source address: packet originator
Destination address: intended recipient
Chapter 3 TCP and IP
16
Operation of TCP and IP
IP implemented in end systems and
routers, relaying data between hosts
 TCP implemented for end-to-end
data transfer only in end systems*,
assuring reliable delivery of blocks
of data
 Each host on sub-network has a
unique IP address
 Each process on each host has a
unique TCP port number

Protocols, Internetworking & the Internet
* Except when?
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TCP/IP Protocol Data Units
(PDUs)
Protocols, Internetworking & the Internet
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TCP/IP Concepts – Data Flow
data
application
transport
network
link
physical
application
transport
network
link
physical
Protocols, Internetworking & the Internet
network
link
physical
application
transport
network
link
physical
data
application
transport
network
link
physical
19
TCP/IP Concepts
Protocols, Internetworking & the Internet
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Routers
Provide connections between
networks
 Accommodate network differences:

–
–
–
–
Addressing schemes
Maximum packet sizes
Hardware and software interfaces
Network reliability
– Congestion/Traffic Management
Protocols, Internetworking & the Internet
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TCP/IP Internetworking
Example
Protocols, Internetworking & the Internet
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Figure 2-8
Protocols, Internetworking & the Internet
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Figure 2-9
Protocols, Internetworking & the Internet
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Figure 2-10
Protocols, Internetworking & the Internet
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