Network Management
LESSON 27

Management of Networks and Resources:

• The need to manage our networks:
  • Having many different protocols and various pieces of hardware internetworked can become very difficult to control.
  • Management software provides the ability to control local and remote devices in an internet, as if all entities were local.

Internet Management:

• Internet Management - software that allows managers to debug problems, control routing, and find computers that violate protocol standards.
• Internetwork Management must occur at all levels of communication:
  • Internetwork Sublayer
  • Network Layer
  • Data Link Layer
  • Physical Layer
• Internet Management functions:
  • Achieve network management goals.
  • Performance testing.
  • System monitoring.
  • Security.
  • Fault tolerance.
  • Configuration management.

Network Management

• Network Management functions:
  • Fault detection.
  • Fault isolation.
  • Fault correction.
  • Meet user requirements for network operation.

Internet Management vs. Network Management:

• Internet management differs from network management:
  • A single manager can control heterogeneous gateways.
  • Controlled entities may not share a common Link Layer Protocol (across different networks and types).
• Example applications for management:
  • Network:
    • LAN management (Novell, StarLAN, Vines, Windows NT)
    • Proprietary management protocols are commonly used to manage local devices only!
  • Internet:
    • Must use a standard network protocol (CMIP, SNMP, or SNMPv2)
    • Can control internet networked devices anywhere, regardless of their physical location.
    • Hewlett Packard - OpenView, and others.

Internet Management at the Application Layer.

• In the TCP/IP Internet, IP gateways form active switches that managers need to examine and control.
• Since gateways connect heterogeneous networks, protocols for internet management operate at the application level and use TCP/IP for message transportation.
• Advantages:
  • One set of management protocols work with all networks.
  • Using IP allows managers to control all gateways connected.
• Disadvantage:
  • All connection components must be working to allow a manager to access a gateway (including: O.S., IP, TCP and UDP).

Management Standards:

• Standards (two parts for each protocol):
  • Defines the format and meaning of messages clients and servers exchange as well as the form of names and addresses.
  • Specifies which data items a gateway must keep as well as names and syntax of the data items.

Common Network Management Protocols.

• Three network management protocols are for use over TCP/IP.
• TCP/IP standard protocols:
  • Simple Network Management Protocol (SNMP)
  • SNMPv2 - Version #2 of SNMP with many enhancements added.
• ISO Open Systems Interconnection management protocol for use over TCP/IP:
  • CMOT - CMIS/CMIP over a TCP connection (Common Management Information Services / Common Management Information Protocol)
  • CMIP is the actual protocol used to provide management features.
  • CMIP is a connection-oriented protocol, so it must use TCP.

Information Categories in the MIB:

MIB Category	Includes Information About
system interfaces address trans. ip icmp tcp udp egp	The host or router operating system Individual network interfaces Address Translation (e.g. ARP mapping) Internet Protocol software Internet Control Message Protocol software Transmission Control Protocol software User Datagram Protocol software Exterior Gateway Protocol software

Management Information Base
(MIB):

• Management Information Base (MIB):
  • The initial cooperative standard (SNMP & CMOT) that specified data items a host or gateway must keep and the operations allowed on each.
  • The original MIB contained 8 only categories of items.
• Advantage:
  • Allows vendors to incorporate software in their products that gather statistics in a universal environment.
• Disadvantage:
  • Competition among vendors and standards committees make this difficult to attain (MIB-II, MIB-II-OIM).
• Since many MIB standards and types now exist, most network management programs must support several management protocols and multiple MIB types.
• An MIB specifies specific network management variables and their meanings, for each protocol.

MIB Variables:

MIB Variable	Category	Meaning
sysUpTime ifMtu ipFragOK's ipRoutingTable icmpInEchos tcpMaxConn udpInDatagrams	system interfaces ip ip icmp tcp udp	# of Network Interfaces MTU for particular interface # of datagrams fragmented IP Routing Table # Echo Requests received Max. TCP connections # UDP datagrams received

Structure for Management Information
(SMI):

• Structure for Management Information (SMI):
  • Specifies a set of rules used to define and identify MIB variables.
• It also:
  • Places restrictions on variable types.
  • Specifies naming rules.
  • Sets rules for defining variable types.
  • Uses a standard notation syntax, known as ASN.1 to define MIB variables.

Abstract Syntax Notation 1
(ASN.1):

• Abstract Syntax Notation 1 (ASN.1):
  • Is a formal language that has two main features:
    • Notation used in documents that people read.
    • Compact encoded representation of the same information used in communication protocols.

MIB Variable Names:

• The names used for MIB variables are based on the object identifier namespace administered by ISO and ITU-T (formerly CCITT).
• They are official standardized names and shared by most MIB types.

Simple Network Management Protocol
(SNMP):

• Simple Network Management Protocol (SNMP):
  • Is an application protocol offering network management services in the Internet Protocol suite (as of 1990)
  • It, as well as SNMPv2, are commonly used by vendors as their primary or secondary internetwork management protocol.
• SNMP defines the:
  • Form and meaning of messages exchanged.
  • Representation of names and values in messages.
  • Administrative relationships among managed gateways.

SNMP
Client/Server Interaction:

• SNMP defines a client/server relationship:
  • The client program (called the network manager) makes virtual connections to a server program (called the SNMP agent) executing on a remote network device.
  • Clients control and interact with network agents (servers) using directives.
• Directives, issued by the network manager client to an SNMP agent, consist of:
  • Identifiers of SNMP variables (referred to as MIB object identifiers or MIB variables).
  • Instructions to either get the value for the identifier, or set the identifier to a new value.

SNMP
Management Information Base:

• The data base controlled by the SNMP agent is referred to as the SNMP Management Information Base (MIB)
• The MIB, similar to the original MIB standard, is a standard set of statistical and control values.
• SNMP additionally allows the extension of these standard values with values specific to a particular agent through the use of private MIBs.

SNMP PDU Operations:

Command	Meaning
get-request get-next-request get-response set-request trap	Fetch a value from a specific variable Fetch a value without knowing its exact name Reply to a fetch operation Store a value in a specific variable Reply triggered by an event

SNMP Strengths:

• SNMP has several strengths:
  • Widespread popularity - SNMP agents are available for network devices ranging from computers, to bridges, to modems, and printers.
  • SNMP is a flexible and extensible management protocol.

SNMP Weaknesses:

• SNMP has several weaknesses:
  • "Simple" Network Management Protocol is actually a highly complicated protocol to implement.
  • SNMP is not a particularly efficient protocol (bandwidth is wasted with needless information and oversized information in directives).

SNMP Message in ASN.1 Format:

SNMP-Message ::=
SEQUENCE {
version INTEGER {
version-1 (0)
},
community
OCTET STRING,
data
ANY
}

SNMP Version 2
(SNMPv2):

• Simple Network Management Protocol 2:
  • Also a standard TCP/IP network management protocol which adds features to the original SNMP that include:
    • Encryption and security features missing from SNMP
    • Allows for bulk information responses for multiple single requests.
    • Supports management requests that exceed the size of the underlying network’s MTU (large requests).
    • Provides the ability to keep multiple management stations apprised of each others’ actions (manager to manager communication).
• SNMPv2 is currently not a complete specification. Vendors and developers are still hammering-out support requirements.
• Many vendors presently support the current specification, but recently, the push toward SNMP upgrade and adoption has stalled.

Common Management Information Protocol
(CMIP):

• CMIP, another protocol used to manage networks, is more complete, yet larger, than SNMP.
• One reason why CMIP has not been commercially popular is due to the fact that it’s an Open Systems Interconnection communication protocol.
• Why is CMIP superior to SNMP?
  • CMIP is superior to SNMP because it can provide greater control over a network by a sysadmin.
• CMIP was designed to build on SNMP by making up for SNMP's shortcomings and becoming a bigger, more detailed network manager.
• Its basic design is similar to SNMP, whereby PDU's are employed as variables to monitor a network.
• CMIP however contains 11 types of PDU's (compared to SNMP's five).
• In CMIP, the variables are seen as very complex and sophisticated data structures, with many attributes. These include :
  • Variable attributes: which represent the variables characteristics (its data type, whether it is writable).
  • Variable behaviors: what actions of that variable can be triggered.
  • Notifications: the variable generates an event report whenever a specified event occurs (terminal shutdown would cause a variable otification event.)

CMIP Advantages and Features:

• Features of the CMIP protocol:
  • Its variables not only relay information to and from the terminal, but they can also be used to perform tasks that would be impossible under SNMP.
  • It addresses many of the shortcomings of SNMP (built in security management devices that support authorization, access control, and security logs)
  • CMIP was funded by not only governments, but also large corporations.

CMIP Disadvantages and Problems:

• Disadvantages of the CMIP protocol:
  • The CMIP protocol takes more system resources than SNMP (by a factor of ten!)
  • CMIP is very difficult to program. Each PDU can include so many different variables that only a few skilled programmers would be able to use them to their full potential.

Management Protocol Support:
Connectionless

• To manage customer premise equipment, SNMP and SNMPv2 are used since they provide simple but effective management functionality without the cost of connection setup.
• SNMP and SNMPv2 are therefore connectionless protocols that use UDP and IP for delivery.

Management Protocol Support:
Connection-Oriented

• To manage large complex networks (common carrier backbones), CMIP is normally required since it provides exhaustive control over many more management items than SNMP.
• This is especially the case for modern ATM networks.
• Most common carrier networks are connection-oriented as is CMIP.

All work was written, produced, and is copyrighted by Daniel Z. Tabor Jr.
Page created by Daniel Z. Tabor Jr. Copyright ©1995 Illusion Industries Inc.