1. Chapter 8: Network Management
Chapter goals:
introduction to network management
motivation
major components
Internet network management framework
MIB: management information base
SMI: data definition language
SNMP: protocol for network management
security and administration
presentation services: ASN.1
8: Network Management

2. Areas of Network Mangement
Performance management - to quantify, measure, report, analyze, and control the performance of different network components;
Fault management - to log, detect and respond to fault conditions in the network;
Configuration management - to track which devices are on the managed network and the hardware and software configurations of these devices;
Accounting management- to specify, log, and control user and device access to network resources;
Security management- to control access to network resources according to some well-defined policy;
8: Network Management

3. What is network management?
autonomous systems (aka “network”): 100s or 1000s of interacting hw/sw components
other complex systems requiring monitoring, control:
jet airplane
nuclear power plant
others?
"Network management includes the deployment, integration
and coordination of the hardware, software, and human
elements to monitor, test, poll, configure, analyze, evaluate,
and control the network and element resources to meet the
real-time, operational performance, and Quality of Service
requirements at a reasonable cost."
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4. Infrastructure for network management
definitions:
managing entity
agent
data
managing
entity
data
managed devices contain
managed objects whose
data is gathered into a
Management Information
Base (MIB)
managed device
agent
data
network
management
protocol
managed device
agent
data
agent
data
managed device
managed device
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5. Network Management standards
OSI CMIP
Common Management Information Protocol
designed 1980’s: the unifying net management standard
too slowly standardized
SNMP: Simple Network Management Protocol
Internet roots (SGMP)
started simple
deployed, adopted rapidly
growth: size, complexity
currently: SNMP V3
de facto network management standard
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6. SNMP overview: 4 key parts
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
major addition in SNMPv3
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7. SMI: data definition language
Purpose: syntax, semantics of management data well-defined, unambiguous
base data types:
straightforward,
OBJECT-TYPE
data type, status, semantics of managed object
MODULE-IDENTITY
groups related objects into MIB module
Basic Data Types
INTEGER
Integer32
Unsigned32
OCTET STRING
OBJECT IDENTIFIER
IPaddress
Counter32
Counter64
Guage32
Time Ticks
Opaque
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8. SNMP MIB MIB module specified via SMI MODULE-IDENTITY
(100 standardized MIBs, more vendor-specific)
MODULE
OBJECT TYPE:
OBJECT TYPE:
OBJECT TYPE:
objects specified via SMI
OBJECT-TYPE construct
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9. SMI: Object, module examples
OBJECT-TYPE: ipInDelivers
MODULE-IDENTITY: ipMIB
ipMIB MODULE-IDENTITY
LAST-UPDATED “ Z”
ORGANZATION “IETF SNMPv2
Working Group”
CONTACT-INFO
“ Keith McCloghrie
……”
DESCRIPTION
“The MIB module for managing IP
and ICMP implementations, but
excluding their management of
IP routes.”
REVISION “ Z”
………
::= {mib-2 48}
ipInDelivers OBJECT TYPE
SYNTAX Counter32
MAX-ACCESS read-only
STATUS current
DESCRIPTION
“The total number of input
datagrams successfully
delivered to IP user-
protocols (including ICMP)”
::= { ip 9}
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10. MIB example: UDP module
Object ID Name Type Comments
UDPInDatagrams Counter32 total # datagrams delivered
at this node
UDPNoPorts Counter32 # underliverable datagrams
no app at portl
UDPInErrors Counter32 # undeliverable datagrams
all other reasons
UDPOutDatagrams Counter32 # datagrams sent
udpTable SEQUENCE one entry for each port
in use by app, gives port #
and IP address
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11. SNMP Naming
question: how to name every possible standard object (protocol, data, more..) in every possible network standard??
answer: ISO Object Identifier tree:
hierarchical naming of all objects
each branchpoint has name, number
ISO
ISO-ident. Org.
US DoD
Internet
udpInDatagrams
UDP
MIB2
management
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12. OSI Object Identifier Tree
Check out
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13. The presentation problem
Q: does perfect memory-to-memory copy solve “the communication problem”?
A: not always!
struct {
char code;
int x;
} test;
test.x = 256;
test.code=‘a’
test.code
test.x a
test.code
test.x a
host 1 format
host 2 format
problem: different data format, storage conventions
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14. Solving the presentation problem
1. Translate local-host format to host-independent format
2. Transmit data in host-independent format
3. Translate host-independent format to remote-host format
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15. ASN.1: Abstract Syntax Notation 1
ISO standard X.680
used extensively in Internet
like eating vegetables, knowing this “good for you”!
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
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16. TLV Encoding Idea: 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 standard
Tag Value Type 1 2 3 4 5 6 9
Boolean
Integer
Bitstring
Octet string
Null
Object Identifier
Real
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17. TLV encoding: example Value, 259 Length, 2 bytes Type=2, integer
Value, 5 octets (chars)
Length, 5 bytes
Type=4, octet string
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18. Basic Concepts of SNMP
An integrated collection of tools for network monitoring and control.
Single operator interface
Minimal amount of separate equipment. Software and network communications capability built into the existing equipment
SNMP key elements:
Management station
Managament agent
Management information base
Network Management protocol
Get, Set and Notify
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19. request/response mode
SNMP protocol
Two ways to convey MIB info, commands:
managing
entity
managing
entity
request
trap msg
response
agent
data
agent
data
Managed device
Managed device
request/response mode
trap mode
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20. Protocol context of SNMP
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21. Proxy Configuration
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22. 8: Network Management

23. SNMP v1 and v2
Trap – an unsolicited message (reporting an alarm condition)
SNMPv1 is ”connectionless” since it utilizes UDP (rather than TCP) as the transport layer protocol.
SNMPv2 allows the use of TCP for ”reliable, connection-oriented” service.
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24. SNMP protocol: message types
Function
GetRequest
GetNextRequest
GetBulkRequest
Mgr-to-agent: “get me data”
(instance,next in list, block)
InformRequest
Mgr-to-Mgr: here’s MIB value
SetRequest
Mgr-to-agent: set MIB value
Agent-to-mgr: value, response to
Request
Response
Trap
Agent-to-mgr: inform manager
of exceptional event
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25. SNMP protocol: message formats
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26. Comparison of SNMPv1 and SNMPv2
Transmit unsolicited information
Agent to manager
SNMPv2-Trap
Trap
Respond to manager request
Agent to manager or Manage to manager(SNMPv2)
Response
GetResponse
Manager to manager
InformRequest
------
Set value for each listed object
Manager to agent
SetRequest
Request multiple values
GetBulkRequest
Request next value for each listed object
GetNextRequest
Request value for each listed object
GetRequest
Description
Direction
SNMPv2 PDU
SNMPv1 PDU
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27. SNMPv1 Community Facility
SNMP Community – Relationship between an SNMP agent and SNMP managers.
Three aspect of agent control:
Authentication service
Access policy
Proxy service
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28. SNMPv1 Administrative Concepts
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29. SNMPv3
SNMPv3 defines a security capability to be used in conjunction with SNMPv1 or v2
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30. Traditional SNMP Manager
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31. SNMPv3 Flow
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32. SNMP3 Message Format with USM
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33. User Security Model (USM)
Designed to secure against:
Modification of information
Masquerade
Message stream modification
Disclosure
Not intended to secure against:
Denial of Service (DoS attack)
Traffic analysis
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34. SNMP v.3 security and administration
encryption: DES-encrypt SNMP message
authentication: compute, send MAC(m,k): compute hash (MAC) over message (m), secret shared key (k)
protection against playback: use nonce
view-based access control
SNMP entity maintains database of access rights, policies for various users
database itself accessible as managed object!
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35. USM Timeliness Mechanisms
USM includes a set of timeliness mechanisms to guard against message delay and message replay.
If a message is considered to be outside of the time window, then the message is considered not authentic, and an error indication is returned to the calling module.
Timeliness checking is done only if the authentication service is in use and the message is authentic, assuring the validity of the message header fields.
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36. 8: Network Management

37. Key localization
For the use of the authentication and privacy services it is required that a secret authentication key and a secret privacy key must be used for communications.
The keys can be generated from the user password using a special algorithm.
A single password could be used to generate a single key for both authentication and encryption.
A more secure scheme is to use two passwords and to generate two different keys.
A localized key is a secret key shared between a user and
a remote SNMP engine.
The process by which a single user key is converted into multiple unique keys is called key localization.
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38. Key Localization Process
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39. View-Based Access Control Model (VACM)
VACM has two characteristics:
Determines whether access to a managed object should be allowed.
Make use of an MIB that:
Defines the access control policy for this agent.
Makes it possible for remote configuration to be used.
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40. Elements of the VACM Model
Group – a set of <securityModel, securityName> tuples on whose behalf objects can be accessed
MIB context - named subset of the object instances in the local MIB
MIB view – specific set of of managed objects
Access policy – particular set of access rights (read, write, notify)
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41. Access determination depends on:
Principal making the access request
Security level requested
Security model
MIB context for the request
Object instance for which access is requested
Type of access requested (read, write notify)
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42. Access control processing
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43. Motivation for VACM
In SNMPv1 the security related information is lumped into a single variable – community. By this flexibility and functionality are lost.
VACM provides the same set of security related information using distinct variables for each item.
This is substantial improvement over SNMPV1. It uncouples various concepts so that values can be assigned to each one separately.
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