Lecture Notes- Network Services - Copy.pptx

© 2008 Cisco Systems, Inc. All rights reserved. Cisco Confidential
Presentation_ID 1
Network Protocols and
Services
Tutor: Dr. Muhammad Ali Kazmi

Presentation_ID 2
Network Protocols
Network Communications Process
 Views of the network
• Small home network
• SOHO (Small Office/Home Office)
• Medium to large networks
• World-wide networks
 Client-Server communications
• Server stores corporate and user files
• Client devices access these files or
services with client software

Presentation_ID 3
Network Protocols
Communications Protocols
 TCP/IP Protocol Suite
• Application Layer
• Transport Layer
• Internet Layer
• Network Access Layer

Presentation_ID 4
Network Protocols
Communications Protocols (Cont.)
 OSI Model (Open Systems Interconnection model)
 Message Delivery
• Unicast – one-to-one
• Multicast – one-to-many
• Broadcast – one-to-all

Presentation_ID 5
Network Protocols
Communications Protocols (Cont.)
 Three important addresses
• Protocol address
• Network host address
• Physical address

Presentation_ID 6
Ethernet and Internet
Protocol (IP)

Presentation_ID 7
Ethernet and Internet Protocol (IP)
Ethernet
 Operates at Layer 1 and 2
• Defined by the IEEE 802.2 and
802.3 standards
 Ethernet responsibilities
• Data encapsulation
• Media access control
• Put bits on the medium
 Ethernet Frame
• Two key identifiers
o Destination MAC address
o Source MAC address
• Uses hexadecimal
IEEE: Institute of Electrical and Electronics Engineers

Presentation_ID 8
IPv4
 Characteristics
• Connectionless
• Unreliable
• Media Independent

Presentation_ID 9
Types of IPv4 Addresses
 Classes – A, B, C, D, and E
 Public
• Can be used on the Internet
 Private
• Used within an organization
• 10.0.0.0 /8
• 172.16.0.0 /12
• 192.168.0.0 /16

Presentation_ID 10
The Default Gateway
 Required IP information to communicate on a TCP/IP
network
• IP address
• Subnet mask
 Default gateway IP address
• Required to send data to a remote
network
• Address is the Layer 3 device,
such as a router connected to
the same network
 IP addressing information
• Configured manually
• Obtained automatically
using DHCP

Presentation_ID 11
Connectivity Verification

Presentation_ID 12
ICMP (Internet Control Message Protocol)
 Used to provide feedback and troubleshoot network problems
 Message types
• Host confirmation – echo request and echo reply with the ping utility
• Destination or service unreachable codes
o 0 – net unreachable
o 1 – host unreachable
o 2 – protocol unreachable
o 3 – port unreachable

Presentation_ID 13
Ping and Traceroute Utilities
 Ping
• Test the local stack
o ping 127.0.0.1
• Test connectivity on the LAN
• Test remote connectivity
 Traceroute – Test the path
a packet takes (Windows:Tracert)
Tracert

Presentation_ID 14
Address Resolution Protocol

Presentation_ID 15
MAC and IP
 Two addresses assigned to an Ethernet device
• MAC address (Layer 2 physical address)
• IP address (Layer 3 logical address)
 A device must have both addresses to communicate with
another TCP/IP-based device
• Uses the source and
destination MAC address
• Uses the source and
destination IP address

Presentation_ID 16
MAC and IP (Cont.)
 When communicating with a device on a remote network, the
destination MAC address is the MAC address of the Layer 3
device interface on the same network as the device
originating the packet.

Presentation_ID 17
ARP
 Protocol used to discover and obtain the destination MAC
address
 Used to resolve IPv4 addresses to MAC addresses
 IPv4 and MAC address mappings kept in an ARP table

Presentation_ID 18
ARP Issues
 ARP Broadcasts – could impact large networks
 ARP Spoofing (ARP poisoning) – security risk

Presentation_ID 19
The Transport Layer

Presentation_ID 20
The Transport Layer
Transport Layer Characteristics
 Tracks individual conversations
 Moves data between applications on network devices
 Segments data
 Identifies applications
using a port number
 Two key protocols
• TCP
• UDP

Presentation_ID 21
The Transport Layer
Transport Layer Characteristics (Cont.)
 TCP
• Used for majority of the
major TCP/IP protocols
• Requires more overhead
(bytes in the header)
• Reliable (3-way handshake)
 UDP
• Used for voice and video
• Fast, fast, fast
• Does not resend dropped
packets

Presentation_ID 22
The Transport Layer
Transport Layer Operation
 Destination port numbers
• Uses well-known port
numbers
 Source port numbers
• Uses dynamic port numbers

Presentation_ID 23
Network Services

Presentation_ID 24
Network Services
DHCP
 Dynamic Host Configuration Protocol (DHCP)
• Provides IP addressing information such as IP address, subnet mask,
default gateway, DNS server IP address, and domain name
• Messages
o Discover
o Offer
o Request
o Ack(nowledge)

Presentation_ID 25
Network Services
DNS
 Dynamic Name System (DNS)
• Manages and provides domain names and associated IP addresses
• Hierarchy of servers
• 90% of malicious software used to attack networks uses DNS to carry
out attack campaigns

Presentation_ID 26
Network Services
HTTP
 Hypertext Transfer Protocol (HTTP)
• Port 80
• Governs the way a web server and client interact
• TCP-based
• Has specific server responses

Presentation_ID 27
Summary

Presentation_ID 28
 A protocol is a set of communication rules defined for a specific purpose.
 The TCP/IP protocol suite is the most widely used set of protocols in the world.
 The TCP/IP protocol stack has four layers. Starting from the top the layers are Application,
Transport, Internet, and Network Access.
 The OSI reference model has seven layers. Starting from the top the layers are
Application, Presentation, Session, Transport, Network, Data Link, and Physical.
 Ethernet operates at Layer 2 of the OSI model and requires the use of a source and
destination MAC address for communicating on a network.
 ARP is used to discover the MAC address associated with a specific IP address.
 IP operates at Layer 3 of the OSI model and requires the use of a source and destination
IP address for communicating on a network.
 ICMP is used for testing connectivity. The ping and traceroute commands are common
ICMP utilities.
Summary

Lecture Notes- Network Services - Copy.pptx

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