Network Management

Network management motivation
• Do not be reactive (troubleshoot and solve problems as they occur), be proactive (plan, monitor, document ahead)
• Must maintain good Performance Monitoring, Support and Documentation
Downtime
The amount of time that a service (such as email or printing), or a server is not
functioning or available
Latency
A delay in the transmission of data, usually caused by excessive traffic
Bottleneck
A device on the network that is slow in
transmitting data, causing delays in the delivery of data
Network Managers
• Manage day-to-day operations of the network
• Provide support to end-users
• Assist senior management on making network decisions
• Ensure the network is operating reliably
Service Level Agreements
Contract defining specific performance metrics and acceptable levels of ISP performance with respect to those metrics (outage, latency etc)
Network Management Platforms
HP’s OpenView, IBM’s Tivoli NetView, Cisco’s Virtual Network Management Center
ISO network management model
• Fault Management (Log, detect and respond to fault conditions in
the network, most common)
• Configuration Management (track which devices are on the managed network)
• Accounting (specify, log and control user and device access to network resources)
• Performance Management (quantify, measure, report, analysis and
control the performance)
• Security Management (control access to network resources according to some well-defined policy)
Network Management standards
• OSI Common Management Information Protocol (too slowly standardised)
• SNMP: Simple Network Management Protocol (adopted rapidly, de facto standard)
Simple Network Management Protocol
• SNMP is the most widely used management framework today.
• Management information base (MIB): distributed information store of network management data
• Structure of Management Information (SMI): data definition language for MIB objects
• SNMP protocol: convey manager←→managed object info, commands
• Security, administration capabilities
Management Information Base
Used for SNMP. Management Information is modeled as (managed) objects and relationships among them. MIB is a collection of
objects, grouped for a specific management purpose.
Structure of Management Information
Syntax, semantics of management data well defined, unambiguous
• base data types
• OBJECT-TYPE
• MODULE-IDENTITY
SNMP Naming
How to name every possible standard object (protocol, data, more..) in every possible network standard??
Answer: ISO Object Identifier tree
Managed Objects
All objects are organized in the global MIB tree (as a leaf or subtree). Each managed object is assigned an object identifier.
SNMP Agent
SNMP agent is software that runs on a piece of network equipment
SNMP manager
An application program that contacts an SNMP agent to query or modify the database at the agent.
SNMP protocol
The application layer protocol used by SNMP agents and managers to send and receive data.
SNMP Traps
The agent sends a trap to the manager to
indicate that something has happened:
0: coldStart
1: warmStart
2: linkDown
3: linkUp
4: authenticationFailure
5: egpNeighborLoss
6: enterpriseSpecific
SNMP Security
SNMPv1 uses plain text community strings for
authentication as plain text. SNMPv2 was supposed to fix security problems, but effort de-railed.
SNMPv3 has many security features: Integrity, Authentication, Privacy
Presentation Problem
1. A finds B’s format and translates into B’s format. A sends.
2. A sends. B learns A’s format and translate into receiver-local format
3. A translates host-independent format and sends. B translates to receiver-local format
TLV Encoding
Transmitted data is self-identifying
– T: data type, one of ASN.1-defined types
– L: length of data in bytes
– V: value of data, encoded according to ASN.1
ASN.1: Abstract Syntax Notation 1
• defined data types, object constructors – like SMI
• BER: Basic Encoding Rules
– specify how ASN.1-defined data objects to be
transmitted
– each transmitted object has Type, Length, Value
(TLV) encoding