Transcript Chapter 4 Transmission Media

System support &
Management Protocols
Lesson 13
NETS2150/2850
School of Information Technologies
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Lecture Outline
Simple Network Management ProtocolSNMP
 Domain Name System- DNS
 Dynamic Host Configuration ProtocolDHCP
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Network Management - SNMP
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Simple Network Management Protocol
Networks are becoming indispensable
More complexity makes failure more likely
Require automatic network management
tools
Standards required to allow multi-vendor
networks
Covering:
– Services
– Protocols
– Management information base (MIB)
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Network Management Systems
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Collection of tools for network management
Single operator interface
Powerful, user friendly command set
Performing most or all management tasks
Minimal amount of separate equipment
– i.e. use existing equipment
View entire network as unified architecture
Active elements provide regular feedback
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Key Elements
Management station or manager
 Agent
 Management information base
 Network management protocol
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Management Station
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Stand alone system or part of shared system
Interface for human network manager
Set of management applications
– Data analysis
– Fault recovery
Interface to monitor and control network
Translate manager’s requirements into
monitoring and control of remote elements
Data base of network management
information extracted from managed entities
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Management Agent
Hosts, bridges, hubs, routers equipped
with agent software
 Allow them to be managed from
management station
 Respond to requests for information
 Respond to requests for action
 Asynchronously supply unsolicited
information
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Management Information Base
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MIB
Representation of network resources as
objects
Each object a variable representing one
aspect of managed object
MIB is collection of access points at agent for
management of station
Objects standardized across class of system
– Bridge, router etc.
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Network Management Protocol
Link between management station and
agent
 TCP/IP uses SNMP
 OSI uses Common Management
Information Protocol (CMIP)
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Protocol Capabilities
Get
 Set
 Notify
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Management Layout
May be centralized in simple network
 May be distributed in large, complex
network
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– Multiple management servers
– Each manages pool of agents
– Management may be delegated to
intermediate manager
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Example of Distributed Network
Management Configuration
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Network Management Protocol
Architecture
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Application-level protocol
 Part of TCP/IP protocol suite
 Runs over UDP
 From management station, three types of SNMP
messages issued
– GetRequest, GetNextRequest, and SetRequest
– Port 161
 Agent replies with GetResponse
 Agent may issue trap message in response to event
that affects MIB and underlying managed
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– Port 162
SNMP v3: The latest version
Addresses security issues of SNMP
v1/2
 RFC 2570-2575
 Proposed standard January 1998
 Defines overall architecture and security
capability
 To be used with SNMP v2
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SNMP v3 Services
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Authentication
– Part of User-Based Security (UBS)
– Assures that message:
• Came from identified source
• Has not been altered
• Has not been delayed or replayed
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Privacy
– Encrypted messages using DES
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Access control
– Can configure agents to provide a number of
levels of access to MIB
– Access to information
– Limit operations
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Domain Name System – DNS
Name Space
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Flat
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Hierarchical
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Domain Name Space
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Was designed in order to have a
hierarchical name space
Label
Domain Name
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Domain name space
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Domain names and labels
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Domain Names: FQDN and PQDN
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Domains
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Distribution of Name Spaces
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Hierarchy of Name Servers
Zone
Root Server
Primary and Secondary Servers
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Hierarchy of name servers
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Zones and domains
Note
A primary server loads all information from the
disk file; the secondary server loads all
information from the primary server.
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DNS In The Internet
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Generic Domain
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Country Domain
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Inverse Domain
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DNS in the Internet
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Generic domains
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New generic domain labels
Label
Description
aero
Airlines and aerospace companies
biz
Businesses or firms (similar to com)
coop
Cooperative business organizations
info
Information service providers
museum Museums and other nonprofit organizations
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pro
Personal names (individuals)
Professional individual organizations
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Country domains
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Inverse domain
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Resolution
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Resolver
Mapping Names to Addresses
Mapping Addresses to Names
Recursive Resolution
Iterative Resolution
Caching
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Recursive resolution
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Query and response messages
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Note:
DNS can use the services of
UDP or TCP,
using the well-known port 53.
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Dynamic Address Configuration
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Each computer attached to the Internet
must have:
– Its own IP address
– Its subnet mask
– The IP address of a Router
– The IP address of a name server
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Usually stored in a config file
– Used at bootup
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Dynamic Address Configuration…
How about first-time bootup?
 Diskless terminal?
 Or, the movement of a computer from
one subnet to another?
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– Protocols needed for on-demand config
(dynamically)
– Example: DHCP
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DHCP
Client-server program
 DHCP server: two databases
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– First one: Statically binds physical addresses to IP
addresses (Static db)
– Second one: makes DHCP dynamic (Dynamic db)
• Temporary IP addresses are assigned consulting available
(unused) address pool
• Valid for a negotiated time period only (leased)
– Must renew or stop using after the lease expires
– Renewal may or may not be granted by the server
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DHCP: Client Transition States
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Recommended Reading:
– Stallings 22.3 (SNMP),
– Forouzan 25 (DNS) & 19.2 (DHCP)
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