Protocols 1

1
Protocols 1

• Objective
• Build a protocol foundation for Client / Server
  programming in an Internet Environment

References RFCs 791, 793, 768, 826
Note RFCs available from http//www.isi.edu/rf
c-editor/
2
Objectives of C/S Architecture

• Improve system performance
• Get centralized applications closer to user
• Improve system reliability
• Improve intersystem (multi-vendor) communications
• Improve resource utilization (PCs on the desktop)
• Move towards standard inter-operating environment

3
Internetwork Communications
4
Layered Protocol Architectures

• Driven by interoperability Concerns
• Divide the communications process into tasks that
  can be managed by a protocol
• Allow multiple protocols to do each of the layers.

5
Simple Layered Model
Application
FTP, e-mail, Client/Server
Transport
Connection Control
Internetwork
Routing
Network Access
Ethernet, fiber, Token Ring
6
Standard Layered Architecture
OSI Model
Internet
Application Layer
TCP / UDP Layer
Internet Protocol
Physical Layer
7
Multiple Hop Communications
Router
Host
Host
8
Internet Addressing

• 32 bit universal identifier (4 octets)
• Normal Site Addresses
• Multicast Address
• Broadcast Address

9
Internet addressing
1 2
3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6
7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 ---------
----------------------- 0
NETWORK Local Address
------------------
--------------
-------------------------
------- 1 0 NETWORK
Local Address ---------
-----------------------
-------------------------
------- 1 1 0
NETWORK Local Address
------------------------
--------
-------------------------
------- 1 1 1 0 MULTICAST ADDRESS
-----------------------
---------
10
Special Internet Addresses

• netid hostid 0s This host
• netid 0s, host id HOST HOST on this net
• netid hostid 1s local net broadcast
• netid NET, hostid 1s broadcast on NET
• high order octet 127, rest anything loopback

11
Domain Name System

• Hierarchical Names
• primus.cstp.umkc.edu
• Domain Name suffixes
• com edu gov
• mil net org
• arpa int country codes
• Domain Name resolution
• name servers
• local caching

12
Data Encapsulation
User Data
Application Layer
TCP
TCP / UDP Layer
IP Layer
PH
Physical Layer
13
Protocol Relationships
------ ----- ----- ----- Telnet
FTP TFTP ... ... ------ -----
----- -----
----- ----- -----
TCP UDP ... ...
----- ----- -----
---------------------
--------- Internet Protocol ICMP
------------------------------

--------------------------- Local
Network Protocol --------------------
-------
14
Ethernet Frame Format

• Preamble Destination Source Type Data
  FCS
• 8 6 6 2 46-1500 4
• Preamble - used for synchronization
• Destination - Ethernet address of destination
• Source - IP address of source
• Ethertype - higher layer protocol type(0800IP)
• Data - IP datagram
• FCS - Frame Check Sequence (32 bit CRC)

15
Ethernet Frame with QoS / VLAN
16 bits 3 bits 1 bit 12 bits
16
Address Resolution Protocol

• Conversion of 32 bit Network Protocol address to
  48 bit Ethernet Address
• Specified in RFC 0826
• Each host must know its own IP address.
• Hosts generally use dynamic discovery to identify
  mappings between IP and Ethernet addresses.
• Ethernet broadcast address FF.FF.FF.FF.FF.FF

17
Internet Protocol functions

• Connectionless Datagram Delivery
• RFC 791
• Benefits of connectionless delivery
• Flexibility (requires little from networks)
• Robustness (datagrams routed independently)
• Connectionless application support

18
IP Design Issues

• Addressing
• Routing
• Datagram lifetime
• Fragmentation and reassembly
• Error control
• Flow control

19
IP Datagram Format
0 1 2
3 0 1 2 3 4 5 6 7 8 9 0 1 2
3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
-------------------------
------- Version IHL Type of
Service Total Length
-------------------------
------- Identification
Flags Fragment Offset
-------------------------
------- Time to Live Protocol
Header Checksum
-------------------------
------- Source
Address
-------------------------
-------
Destination Address
-------------------------
------- Options
Padding
-------------------------
-------
20
IP Service Primitives

• Services offered to higher layers
• Send
• (source address, destination address, protocol,
  type of service indicators, identifier, dont
  fragment indicator, time to live, data length,
  option data, data)
• Deliver
• (Source address, destination address, protocol.
  type of service indicators, data length, option
  data, data)

21
User Datagram Protocol Functions

• Connectionless Data Transfer
• Unreliable

22
UDP Header
0 7 8 15 16 23 24 31
--------------------------------
Source Destination Port
Port ------------------------
--------
Length Checksum
--------------------------------
data
octets ... ---------------- ...

23
UDP pseudo Header
0 7 8 15 16 23 24 31
--------------------------------
source address --------------------
------------ destination address
-------------------------------- zero
protocol UDP length ------------------
--------------
24
Summary

• Reviewed layered Protocol Architecture
• Discussed Internet Naming and Addressing
• Discussed Internet Protocol (IP) Functions and
  Header