CHAPTER 30
Internet 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
2
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.
4
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
6
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.
8
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
9
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
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udpInDatagrams udp # of UDP datagrams received
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
13
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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18
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
25
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. 26
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 28
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 29
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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THANK YOU