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Telecommunications Systems Engineer Course
Data Communications
Section 8
Dr. Wenyuan Xu
2-24-2011

Outline
? What is network management?
? Internet-standard management framework
– Structure of Management Information: SMI
– Management Information Base: MIB
– SNMP Protocol Operations and Transport Mappings
– Security and Administration
? ASN.1
Network Management 9-2

What is network management?
? autonomous systems (aka “network”): 100s or 1000s of
interacting hardware/software 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."

Infrastructure for network management
agent data
agent data
agent data
agent data
managed device
managed device
managed device
managed device
managing
entity
data
network
management
protocol
definitions:
managed devices contain
managed objects whose
data is gathered into a
Management Information
Base (MIB)
managing entity

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

Outline
? ASN.1

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

SMI: data definition language
Purpose: syntax, semantics of
management data well-
defined, unambiguous
? base data types:
– straightforward, boring
? 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 IDENTIFIED
IPaddress
Counter32
Counter64
Guage32
Time Ticks
Opaque

SNMP MIB
OBJECT TYPE:
OBJECT TYPE:
OBJECT TYPE:
objects specified via SMI
OBJECT-TYPE construct
MIB module specified via SMI
MODULE-IDENTITY
(100 standardized MIBs, more vendor-specific)
MODULE

SMI: Object, module examples
OBJECT-TYPE: ipInDelivers MODULE-IDENTITY: ipMIB
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}
ipMIB MODULE-IDENTITY
LAST-UPDATED “941101000Z”
ORGANZATION “IETF SNPv2
Working Group”
CONTACT-INFO
“ Keith McCloghrie
……”
DESCRIPTION
“The MIB module for managing IP
and ICMP implementations, but
excluding their management of
IP routes.”
REVISION “019331000Z”
………
::= {mib-2 48}

MIB example: UDP module
Object ID Name Type Comments
1.3.6.1.2.1.7.1 UDPInDatagrams Counter32 total # datagrams delivered
at this node
1.3.6.1.2.1.7.2 UDPNoPorts Counter32 # underliverable datagrams
no app at portl
1.3.6.1.2.1.7.3 UDInErrors Counter32 # undeliverable datagrams
all other reasons
1.3.6.1.2.1.7.4 UDPOutDatagrams Counter32 # datagrams sent
1.3.6.1.2.1.7.5 udpTable SEQUENCE one entry for each port
in use by app, gives port #
and IP address

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
1.3.6.1.2.1.7.1
ISO
ISO-ident. Org.
US DoD
Internet
udpInDatagrams
UDP
MIB2
management

OSI
Object
Identifier
Tree
Check out www.alvestrand.no/harald/objectid/top.html

SNMP protocol
Two ways to convey MIB info, commands:
agent data
Managed device
managing
entity
response
agent data
Managed device
managing
entity
trap msg
request
request/response mode trap mode

SNMP protocol: message types
GetRequest
GetNextRequest
GetBulkRequest
Mgr-to-agent: “get me data”
(instance,next in list, block)
Message type Function
InformRequest Mgr-to-Mgr: here’s MIB value
SetRequest Mgr-to-agent: set MIB value
Response Agent-to-mgr: value, response to
Request
Trap Agent-to-mgr: inform manager
of exceptional event

SNMP protocol: message formats

SNMP security and administration
? encryption: DES-encrypt SNMP message
? authentication: compute, send MIC(m,k):
compute hash (MIC) 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!

Outline
? The presentation problem: ASN.1

The presentation problem
Q: does perfect memory-to-memory copy
solve “the communication problem”?
A: not always!
problem: different data format, storage conventions
struct {
char code;
int x;
} test;
test.x = 256;
test.code=‘a’
a
00000001
00000011
a
00000011
00000001
test.code
test.x
test.code
test.x
host 1 format host 2 format

A real-life presentation problem:
aging 60’s
hippie
2007 teenager
grandma

Presentation problem: potential solutions
1. Sender learns receiver’s format. Sender translates into
receiver’s format. Sender sends.
– real-world analogy?
– pros and cons?
2. Sender sends. Receiver learns sender’s format.
Receiver translate into receiver-local format
– real-world-analogy
– pros and cons?
3. Sender translates host-independent format. Sends.
Receiver translates to receiver-local format.
– real-world analogy?
– pros and cons?

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
aging 60’s
hippie 2007 teenager
grandma

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

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
1
2
3
4
5
6
9
Boolean
Integer
Bitstring
Octet string
Null
Object Identifier
Real
Tag Value Type

TLV
encoding:
example
Value, 5 octets (chars)
Length, 5 bytes
Type=4, octet string
Value, 259
Length, 2 bytes
Type=2, integer

Network Management:
summary
? network management
– extremely important: 80% of network “cost”
– ASN.1 for data description
– SNMP protocol as a tool for conveying information
? Network management: more art than science
– what to measure/monitor
– how to respond to failures?
– alarm correlation/filtering?

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Datacom Section 8 - NetworkManagment.ppt

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