Transcript Network Management

SNMP

Where did it come from ?
– Internet Engineering Task Force
» Network Management Area
– SNMP V1
– MIB definitions
– SNMPV2
Syntax

uses ASN.1 (Abstract Syntax Notation)
– binary encoding
02 01 06is a 1 byte integer, value 6

Primitive Types
INTEGER, OCTECT STRING, OBJECT IDENTIFIER, NULL

Constructor Types
SEQUENCE <primitive-type> ...
SEQUENCE OF <primitive-type> ...
ie. a record
ie. an array
Syntax

Defined Data Types
IpAddress
Counter
Gauge
TimeTicks
what you expect
non-negative integer that wraps
non-negative integer that latches
time in hundredths of seconds
SNMP NAMES
SNMP Name St ructure
1 - iso
3 - o rg
6 - d od
1 - In tern et
1 - d irecto ry
2 - mgmt
3 - exp t
1 - mib
1 - system
1 - sysDescr
1 - Enterp rise
2 - in terfaces
2 - sysOb jectID
4 - p rivate
9 - cisco
1 - ifTabl e
1 - ifEn try
1 - ifIn dex
2 - ifDescr
3 - ifType
.. .... ..
10 - ifIn Octets
SNMP

Management Information Base (MIB)
– "database"of network objects
– Groups:
» System, Interfaces, Address Translation, IP, ICMP,
TCP, UDP, EGP
– "Access" and "Status" attributes
– actual variables are "instances" of OIDs
1.3.6.1.2.1.1.1.0
sysDescr
1.3.6.1.2.1.2.1.1.10.3 ifInOctets for interface 3
1.3.6.1.2.1.4.21.1.7.130.56.0.0
ipRouteNextHop for network 130.56.0.0
SNMP

The SNMP protocol itself
– allows inspection and alteration of MIB
variables

UDP Based
– not acknowledged transactions

PUT, GET, GET-NEXT operators
SNMPv1 Protocol continued...
get_request
get_response
port 161
get_response
port 161
get_next_request
Manager
Agent
set_request
get_response
port 162
trap
port 161
port 161
SNMPv1 Packet Format
UDP
PDU Request Error Error
Version Community
name value name ...
Header
Type ID Status Index
SNMP

SNMP Traps
–
–
–
–
–
–
–
unsolicited notification of events
can include variable list
ColdStart, WarmStart
LinkUp, LinkDown
Authentication Failure
EGP Neighbour Loss
Enterprise Specific
Network Management Software

SNMP Agents
– provided by all router vendors
– many expanded (enterprise) MIBs
– bridges, wiring concentrators, toasters
Network Management Software

Public Domain
– Application Programming Interfaces available
from CMU and MIT
– include variety of applications
Network Management Software

Commercially
– many offerings, UNIX and PC based
» HP OpenView
» SunNet Manager
» Cabletron Spectrum
» *MANY* others
Applications
Receiving MTA
Sending MTA
Open TCP connection on port 25
220 ***** [id, ready, time]
Hello name
250 [id, Hello pleased to meet….]
Mail From: [email protected]
250 [email protected] Sender OK
RCPT To: [email protected]
250 [email protected] Recipient OK
DATA
…………….
354 Mail goes here, end with a “.” line
“.”
250 Mail Accepted
QUIT
221 Delivering Mail

Example of mail retrieval using POP
POP Client
POP Mail Server / Local MTA
USER joe_bloggs
+OK joe_bloggs
PASS mypassword
+OK joe_bloggs has 10 messages
RETR 1
+OK msg 1 (100 bytes)
From: ……
Subject: Last week of lectures……
…………….
DELE 1
+OK ……….
QUIT
+OK ………...
Network Address Translation (NAT)
NAT
Inside
station B
IP :10.2.2.1
Outside
Interface E1
Interface E0
IP :10.1.1.1
IP :171.69.20.1
station A
IP :171.69.2.1
NAT router
Internet
IP :10.3.3.1
station D
NAT Pool
IP :171.69.3.1
171.69.89.1
station C
NAT Table
protocol
Inside source
Address : port
Outside source
Address : port
Outside Destination
Address : port
TCP
10.2.2.1:1024
171.69.89.1:1024
171.69.2.1:23
TCP
103.3.1:1723
171.69.89.1:1723
171.69.3.1:23