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CHAPTER 30Internet Management

Albert 30.1, 2, 3

Yifan 30.4, 5, 6, 7

Jianxin 30.8

Huaidong 30.9

Lai Yee 30.10

Daniel 30.11, 12, 13

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Internet Management

Activities in Internet management:

Debug problems Control routing Find computer that violate protocol standard

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Network Management

Originally, many wide area networks included management protocols as part of their link level protocols.

Advantage:

Managers were often able to control switches even if higher level protocols failed.

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Internet management differs from network management

A single manager can control heterogeneous devices including IP routers, bridges, modems, work-stations, and printers.

The controlled entities may not share a common link level protocol.

The set of machines a manager controls may lie at arbitrary points in an internet.

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Internet management operates at the application level

Advantages:• One set of protocol can be used for all networks.• Same protocols can be used for all managed devices.• A manager can control the routers across an entire

TCP/IP internet without having direct attached to every physical network or router.

Disadvantage:• If the operating system, IP software, or transport

protocol software does not work correctly, the manager may not be able to contact a router that needs managing.

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Architectural Model

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Architectural Model

• Client software usually runs on the manager’s workstation.

• Each participating router or host runs a server program called management agent.

• Most managers only control devices at their local sites; a large site may have multiple managers.

Internet management software uses an authentication mechanism to ensure only authorized managers can access or control a particular device.

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Protocol Framework It’s all about management information!

SNMP How to exchange?

MIB How to store and operate?

SMI How to define and identify?

ASN. 1 Formal notation used by SMI.

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SNMP v3 – how to communicate?

Stands for Simple Network Management Protocol version 3

A standard Network Management Protocol

Defines:- message format, form of names and

addresses- how to use transport protocol- set of operations and their meaning- approach is minimalistic

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MIB – How about data? Stands for Management Information Base Defines:

- What data should be kept for the manager?- What operations are allowed on these data?- Categories of data - Variables in each category

MIB definition is independent of the network management protocol.

- All managed devices speaks the same language (MIB)

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__MIB category includes informationabout________

system The host or router operating system

interfaces Individual network interfaces

at Address translation (e.g. ARP)

ip Internet protocol software

icmp Internet Control Protocol software

tcp Tansmission Control Protocol software

udp User datagram Protocol software

ospf Open shortest path first software

bgp Border Gateway Protocol software

rmon Remote network monitoring

rip-2 Routing Information Protocol software

dns Domain Name System software

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MIB Variable Category Meaning______________

sysUptime system Time since last reboot

ifNumber interfaces Number of network interface

ifMTU interfaces MTU for a particular interface

ipDefaultTTL ip Value IP uses in TTL field

ipInReceives ip Number of datagrams received

ipForwdatagrams ip Number of datagrams forwarded

ipOutNoroutes ip Number of routing failures

ipReasmOKs ip Number of datagrams reassembled

ipFragOKs ip Number of datagrams fragmented

ipRoutingTable ip IP routing table

icmpInEchos icmp # of ICMP echo requests received

tcpRtoMin tcp Min retransmision time TCP allows

tcpMaxConn tcp Max TCP connection allowed

tcpInSegs tcp # of segments TCP has received

udpInDatagrams udp # of UDP datagrams received

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MIB variables

Each variable can be stored as

- A single integer

- A complex structure

e.g., an entire Routing Table

Also defines table entries. Presentation only has logical meaning.

- Router may use different internal data structures

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SMI – rules to define and identify variables

Stands for Structure of Management Information

Specifies:

- What variable types are allowed?

- What naming rules should be followed?

- How to refer to the tables of values?

e.g., the IP routing table

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ASN. 1 – a formal notation used by SMI

Stands for ISO’s Abstract Syntax Notation 1 A formal notation of defining variable names

and types

- In documents: human can read

- In communication: compact encoded representation

Benefits:

- Makes the form and contents of variables unambiguous.

- Simplifies the implementation of protocols

- guarantees interoperability

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30.8 Structure And Representation Of MIB Object Names --- Jianxin

Object Identifier Namespace:

1. Names used for MIB variables are taken from the object identifier namespace administered by ISO and ITU.

2. The object identifier namespace is absolute, meaning that names are structured to make them globally unique.

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Hierarchy of namespace

The root of the object identifier hierarchy is unnamed.

It has three direct descendants managed by: ISO ITU jointly by ISO and ITU

The descendants are assigned both short text strings and integers.

ISO has allocated one subtree for use by other national or international standards organizations.

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Name an object and MIB categories

The name of an object in the hierarchy is the sequence of numeric labels on the nodes along a path from the root to the object.

The sequence is written with periods separating the individual components.

example: 1.3.6.1.2 --- denotes the node ‘mgmt’

The MIB groups variables into categories, each category is the sub-tree of the ‘mib’ node of the object identifier namespace.

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Simple category naming examples

The category labeled ip has been assigned the value 4.

The names of all MIB variables corresponding to ip have an identifier that begins with the prefix:

1.3.6.1.2.1.4

The textual label would be:

iso.org.dod.internet.mgmt.mib.ip When network management protocols use names of

MIB variables in messages, each name has a suffix appended. For simple variables, the suffix is 0.

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Complex example

How about the variable ipAddrTable A list of the IP addresses for each network

interface It’s a sub-tree under ip node, with prefix:

iso.org.dod.internet.mgmt.mib.ip.ipAddrTable

How to represent such data structures. MIB defines a uniform, virtual interface to

access data

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ipAddrTable can be defined as:

ipAddrTable ::= SEQUENCE OF IpAddrEntry

Each entry in the array is defined by five fields:

IpAddrEntry ::= SEQUENCE {

ipAdEntAddr IpAddress,

ipAdEntIfIndex INTEGER,

ipAdEntNetMask IpAddress,

ipAdEntBcastAddr IpAddress,

ipAdEntReasmMaxSize

INTEGER(0..65535) }

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Assign numeric values to entry and each item of the entry:

ipAddrEntry {ipAddrTable 1}

ipAdEntNetMask{ipAddrEntry 3} Use a suffix appended onto the name to

select a specific element in the table, not the index.

suffix = IP address

variable name.IP address

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Simple Network Management Protocol (SNMP)

Huaidong Meng

Instructor: Dr. Sharon Hall

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Simple Network Management protocol

Network Management protocol:– specify communication between client

program a network manager invoked and server program executing on a host or router.

– which defines the form and meaning of message exchanged

– representation of names and values of message

– define administrative relationships among routers between managed.

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Network Management Protocol

Allow the manager– Reboot the system– Add or delete the router– Disable or enable a particular network interface– Remove cached address binding

The main disadvantage: the resulting complexity– For example, the command to delete a routing

table entry differs from the command to disable an interface.

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SNMP takes an interesting alternative approach to network management

casts all operations in a fetch-store paradigm, instead of defining a large set of commands: – Stability

• Its definition remains fixed.

– Simple to implement, understand, and debug• It avoids the complexity of having special cases

for each command.

– Flexible• Accommodate arbitrary commands in an elegant

framework

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SNMP commands get-request fetch a value from a specific

variable get-next-request fetch a value without

knowing its exact name get bulk-request fetch a large volume of data

Response a response to any of above request

set-request store a value in a specific variable

inform-request reference to a third-party data

snmpv2-trap reply triggered by an event

Report undefined at present

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Searching Table Using Names get-next-request

– Allows a client to iterate through a table by supplies a prefix of a valid object identifier, without knowing how many items the table contains.

– The server returns a network mask field of the first entry in ipAddrTable, and the client uses the full object identifier returned by the server to request the next item in the table.

– See page 566 for the example

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SNMP Message Format

SNMPv3Message ::=

SEQUENCE {

msgVersion INTEGER (0..2147483647),

msgGlobalData HeaderData,

msgSecurityParameters OCTET STRING,

msgData ScopedPduData

}

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Definition of SNMP HeaderData

HeaderData ::= SEQUENCE {

msgID INTEGER (0..2147483647)

msgMaxSize INTEGER (484..2147483647)

msgFlags OCTET STRING (SIZE(1))

msgSecurityModel INTEGER (1..2147483647)

}

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Definition of SNMP PDU

PDU ::=

CHOICE {

get-request

get-next-request

get-bulk-request

response

set-request

inform request

snmpV2-trap

report

}

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Internet Management-Example Encoded SNMP Message

Figure 30.11 contains an encoded get-request message for data item sysDescr

Each term used is further defined until it can be defined by primitive data type, e.g. integer, string. -Let’s compare the message with the specified format

Hence, the encoded items have variable-length fields

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Internet Management-New Features In SNMPv3

Scope: Security and administration Goal: generality, flexibility and ease of admin. Example new features

– Message Authentication– Privacy– Authorization & View-based Access Control– Remote Configuration

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Internet Management-Summary

An application level client program accesses and controls agents running on devices

SNMP is the standard TCP/IP network management protocol that uses 2 conceptual operation, fetch and store

A companion standard, MIB, defines the variables that are maintained by the agents

MIB variables are described by ASN.1, which uses a hierarchical namespace to ensure global uniqueness

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