ICT 6621 : Advanced NetworkingKhaled Mahbub, IICT, BUET, 2008 Lecture 13 Network Management

Khaled Mahbub, IICT, BUET, 2008 ICT 6621 : Advanced Networking

Lecture 13

Network Management


Outline• Network management concepts

• Internet-standard management framework (SNMP)– Structure of Management Information: SMI– Management Information Base: MIB– SNMP Protocol Operations and Transport Mappings– Security and Administration

• Abstract Syntax Notation One (ASN.1)


Network Management• autonomous systems (aka “network”): 100s or 1000s of interacting

hardware/software components• "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."

• More specifically network management comprises of:– Performance management: quantify, measure, report, analyze and

control the performance (e.g., utilization, throughput) of different network components.

– Fault management: log, detect, and respond to fault conditions in the network.

– Configuration management: track which devices are on the managed network and the hardware and software configurations of these devices.

– Accounting management: specify, log, and control user and device access to network resources.

– Security management: control access to network resources according to some well-defined policy.


Infrastructure for Network Management

• definitions:

agent data

agent data

agent data

agent data

managed device

managed device

managed device

managed device

managingentity data

networkmanagement

protocol

managed device is a piece of network equipment, e.g. host, router (including its software) that contains managed objects e.g. interface card, whose data is gathered into a Management Information Base (MIB)

managing entity is an application that controls the collection,processing, analysis, and/or display of network management information.

network management protocol runs between the managing entity and the managed devices to query the status of managed devices and take actions in these devices.


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






SNMP overview: 4 key parts• Management information base (MIB):

– distributed information store of network management data. Management information is represented as a collection of managed objects. A MIB object might be a counter, such as the number of IP datagrams discarded at a router due to errors in an IP datagram header or the number of carrier sense errors in an Ethernet interface,

• Structure of Management Information (SMI):– data definition language for MIB objects

• SNMP protocol– convey manager<->managed object information,

commands• security, administration capabilities

– major addition in SNMPv3


SMI: Data Definition LanguagePurpose: syntax, semantics of management data well-defined,

unambiguous• base data types:

– INTEGER, Integer32, Unsigned32, OCTET STRING, OBJECT IDENTIFIED, IP address, Counter32, Counter64, Guage32, Time Ticks

• OBJECT-TYPE– used to specify the data type, status, and semantics of a managed

object. The OBJECT-TYPE construct has four clauses. The SYNTAX clause specifies the basic data type associated with the object. The MAX-ACCESS clause specifies whether the managed object can be read, written, created, or have its value included in a notification. The STATUS clause indicates whether object definition is current and valid, obsolete or deprecated. The DESCRIPTION clause contains a human-readable textual definition of the object;

• MODULE-IDENTITY– groups related objects into MIB module


SMI: Data Definition Language• NOTIFICATION-TYPE

– is used to specify information regarding "InformationRequest" messages generated by an agent, or a managing entity. This information includes a textual DESCRIPTION of when such messages are to be sent, as well as list of values to be included in the message generated.

• MODULE-COMPLIANCE – defines the set of managed objects within a module that an

agent must implement.

• AGENT-CAPABILITIES – specifies the capabilities of agents with respect to object and

event notification definitions.


SNMP MIB

objects specified via SMIOBJECT-TYPE construct

MIB module specified via SMI MODULE-IDENTITY

OBJECT TYPE:

OBJECT TYPE:OBJECT TYPE:

MODULE

100 standardized MIBs, even more vendor-specific are defined, e.g.

[RFC 2011] specifies the MIB module that defines managed objects for managing implementations of the Internet Protocol (IP) and its associated Internet Control Message Protocol (ICMP).

[RFC 2012] specifies the MIB module for TCP and [RFC 2013] specifies the MIB module for UDP.


SMI: Object, Module Examples

OBJECT-TYPE: ipInDelivers

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}

MODULE-IDENTITY: ipMIBipMIB 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}

ipInDeliversobject type definition(from [RFC 2011]) defines a 32-bit counter which keeps track of the numberof IP datagrams that were received at the managed node

ipMIB module definition for managementof the IP protocol:


SNMP Namingquestion: 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 branch point has name, number

1.3.6.1.2.1.7.1

ISOISO-ident. Org.

US DoDInternet

udpInDatagramsUDPMIB2management


OSI Object Identifier Tree


MIB Example: UDP Module

Object ID Name Type Comments1.3.6.1.2.1.7.1 UDPInDatagrams Counter32 total number of UDP datagrams

delivered to UDP users

1.3.6.1.2.1.7.2 UDPNoPorts Counter32 total number of received UDP

datagrams for which there was no

application at the destination port

1.3.6.1.2.1.7.3 UDInErrors Counter32 number of received UDP datagrams that could not be delivered for reasons other than the lack of an application at the destination port

1.3.6.1.2.1.7.4 UDPOutDatagrams Counter32 total number of UDP datagrams sent from this entity

1.3.6.1.2.1.7.5 udpTable SEQUENCE of UdpEentry

a sequence of UdpEntry objects, one for each port that is currently open by an application, giving the IP address and the port number used by application


SNMP ProtocolTwo ways to convey MIB information and commands:

agent data

Managed device

managingentity

trap msg

agentdata

Managed device

managingentity

response

request

request/response mode: used to query (retrieve) or modify (set) MIB object values associated with a managed device.

trap mode: used to notify amanaging entity of an exceptional situation that has resulted in changes to MIB object values.


SNMP Protocol: Message Types

GetRequestGetNextRequestGetBulkRequest

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 managerof exceptional event


SNMP Protocol: Message Formats


SNMP Protocol: Message Formats


SNMP Applications

• Typically a SNMP applications consist of two parts:– managing entity includes

• a command generator: generates the GetRequest, GetNextRequest, GetBulkRequest and SetRequest PDUs

• notification receiver: receive and process Trap PDUs• proxy forwarder: forwards request, notification, and response

PDUs.

– agent in managed device includes • a command responder: receives, processes and replies to

received GetRequest, GetNextRequest, GetBulkRequest and SetRequest PDUs.

• notification originator: generates Trap PDUs.


SNMP Engine and Application


SNMP Security and Administration• encryption: DES-encrypt SNMP message • authentication: compute, send MIC(m,k):

compute hash (Message Integrity Code: MIC) over message (m), and 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!






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 = 259;test.code=‘a’

a0000000100000011

a

0000001100000001

test.codetest.x

test.code

test.x

host 1 format host 2 format

259 in decimal is equivalent to binary 1 00000011


Presentation Problem: Potential Solutions1. Sender learns receiver’s format. Sender

translates into receiver’s format. Sender sends.

2. Sender sends. Receiver learns sender’s format. Receiver translate into receiver-local format

3. Sender translates host-independent format. Sends. Receiver translates to receiver-local format.


Solving the Presentation Problem1. Translate local-host format to host-independent format2. Transmit data in host-independent format3. Translate host-independent format to remote-host format


ASN.1: Abstract Syntax Notation One• ISO standard X.680

– used extensively in Internet• 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

1234569

BooleanIntegerBitstringOctet stringNullObject IdentifierReal

Tag Value Type


TLV Encoding: Example

Value, 5 octets (chars)Length, 5 bytes

Type=4, octet string

Value, 259Length, 2 bytes

Type=2, integer


Reading Material• Chapter 8 – text3 (Kurose)

• Chapter 25 – text1 (Stevens)

Documents

ICT 6621 : Advanced NetworkingKhaled Mahbub, IICT, BUET, 2008 Lecture 13 Network Management