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Cmip vs snmp network management protocols

CMIP vs. SNMP : Network Management

Imagine yourself as a network administrator, responsible for a 2000 user network.

This network reaches from California to New York, and some branches over seas. In

this situation, anything can, and usually does go wrong, but it would be your job as a

system administrator to resolve the problem with it arises as quickly as possible. The

last thing you would want is for your boss to call you up, asking why you haven't done

anything to fix the 2 major systems that have been down for several hours. How do

you explain to him that you didn't even know about it? Would you even want to tell

him that? So now, picture yourself in the same situation, only this time, you were

using a network monitoring program. Sitting in front of a large screen displaying a

map of the world, leaning back gently in your chair. A gentle warning tone sounds, and

looking at your display, you see that California is now glowing a soft red in color, in

place of the green glow just moments before. You select the state of California, and it

zooms in for a closer look. You see a network diagram overview of all the computers

your company has within California. Two systems are flashing, with an X on top of

them indicating that they are experiencing problems. Tagging the two systems, you

press enter, and with a flash, the screen displays all the statitics of the two systems,

including anything they might have in common causing the problem. Seeing that both

systems are linked to the same card of a network switch, you pick up the phone and

give that branch office a call, notifying them not only that they have a problem, but

how to fix it as well.

Early in the days of computers, a central computer (called a mainframe) was

connected to a bunch of dumb terminals using a standard copper wire. Not much

thought was put into how this was done because there was only one way to do it: they

were either connected, or they weren't. Figure 1 shows a diagram of these early

systems. If something went wrong with this type of system, it was fairly easy to

troubleshoot, the blame almost always fell on the mainframe system.

Shortly after the introduction of Personal Computers (PC), came Local Area

Networks (LANS), forever changing the way in which we look at networked systems.

LANS originally consisted of just PC's connected into groups of computers, but soon

after, there came a need to connect those individual LANS together forming what is

known as a Wide Area Network, or WAN, the result was a complex connection of

computers joined together using various types of interfaces and protocols. Figure 2

shows a modern day WAN. Last year, a survey of Fortune 500 companies showed that

15% of their total computer budget, 1.6 Million dollars, was spent on network

management (Rose, 115). Because of this, much attention has focused on two families

of network management protocols: The Simple Network Management Protocol

(SNMP), which comes from a de facto standards based background of TCP/IP

communication, and the Common Management Information Protocol (CMIP), which

derives from a de jure standards-based background associated with the Open Systems

Interconnection (OSI) (Fisher, 183).

In this report I will cover advantages and disadvantages of both Common

Management Information Protocol (CMIP) and Simple Network Management Protocol

(SNMP)., as well as discuss a new protocol for the future. I will also give some good

reasons supporting why I believe that SNMP is a protocol that all network

administrators should use.

SNMP is a protocol that enables a management station to configure, monitor, and

receive trap (alarm) messages from network devices. (Feit, 12). It is formally specified

in a series of related Request for Comment (RFC) documents, listed here.

RFC 1089 - SNMP over Ethernet

RFC 1140 - IAB Official Protocol Standards

RFC 1147 - Tools for Monitoring and Debugging TCP/IP

Internets and Interconnected Devices

[superceded by RFC 1470]

RFC 1155 - Structure and Identification of Management

Information for TCP/IP based internets.

RFC 1156 - Management Information Base Network

Management of TCP/IP based internets

RFC 1157 - A Simple Network Management Protocol

RFC 1158 - Management Information Base Network

Management of TCP/IP based internets: MIB-II

RFC 1161 - SNMP over OSI

RFC 1212 - Concise MIB Definitions

RFC 1213 - Management Information Base for Network Management

of TCP/IP-based internets: MIB-II

RFC 1215 - A Convention for Defining Traps for use with the SNMP

RFC 1298 - SNMP over IPX (SNMP, Part 1 of 2, I.1.)

The first protocol developed was the Simple Network Management Protocol

(SNMP). It was commonly considered to be a quickly designed "band-aid" solution to

internetwork management difficulties while other, larger and better protocols were

being designed. (Miller, 46). However, no better choice became available, and SNMP

soon became the network management protocol of choice.

It works very simply (as the name suggests): it exchanges network packets through

messages (known as protocol data units (PDU)). The PDU contains variables that

have both titles and values. There are five types of PDU's which SNMP uses to

monitor a network: two deal with reading terminal data, two with setting terminal data,

and one called the trap, used for monitoring network events, such as terminal start-ups

or shut-downs.

By far the largest advantage of SNMP over CMIP is that its design is simple, so it is

as easy to use on a small network as well as on a large one, with ease of setup, and lack

of stress on system resources. Also, the simple design makes it simple for the user to

program system variables that they would like to monitor. Another major advantage to

SNMP is that is in wide use today around the world. Because of it's development

during a time when no other protocol of this type existed, it became very popular, and

is a built in protocol supported by most major vendors of networking hardware, such as

hubs, bridges, and routers, as well as majoring operating systems. It has even been put

to use inside the Coca-Cola machines at Stanford University, in Palo Alto, California

(Borsook, 48). Because of SNMP's smaller size, it has even been implemented in

such devices as toasters, compact disc players, and battery-operated barking dogs. In

the 1990 Interop show, John Romkey, vice president of engineering for Epilogue,

demonstrated that through an SNMP program running on a PC, you could control a

standard toaster through a network (Miller, 57).

SNMP is by no means a perfect network manager. But because of it's simple

design, these flaws can be fixed. The first problem realized by most companies is that

there are some rather large security problems related with SNMP. Any decent hacker

can easily access SNMP information, giving them any information about the network,

and also the ability to potentially shut down systems on the network. The latest version

of SNMP, called SNMPv2, has added some security measures that were left out of

SNMP, to combat the 3 largest problems plaguing SNMP: Privacy of Data (to prevent

intruders from gaining access to information carried along the network), authentication

(to prevent intruders from sending false data across the network), and access control

(which restricts access of particular variables to certain users, thus removing the

possibility of a user accidentally crashing the network). (Stallings, 213)

The largest problem with SNMP, ironically enough, is the same thing that made it

great; it's simple design. Because it is so simple, the information it deals with is

neither detailed, nor well organized enough to deal with the growing networks of the


This is mainly due to the quick creation of SNMP, because it was never designed to be

the network management protocol of the 1990's. Like the previous flaw, this one too

has been corrected with the new version, SNMPv2. This new version allows for more

in-detail specification of variables, including the use of the table data structure for

easier data retrieval. Also added are two new PDU's that are used to manipulate the

tabled objects. In fact, so many new features have been added that the formal

specifications for SNMP have expanded from 36 pages (with v1) to 416 pages with

SNMPv2. (Stallings, 153) Some people might say that SNMPv2 has lost the simplicity,

but the truth is that the changes were necessary, and could not have been avoided.

A management station relies on the agent at a device to retrieve or update the

information at the device. The information is viewed as a logical database, called a

Management Information Base, or MIB. MIB modules describe MIB variables for a

large variety of device types, computer hardware, and software components. The

original MIB for Managing a TCP/IP internet (now called MIB-I) was defined in RFC

1066 in August of 1988. It was updated in RFC 1156 in May of 1990. The MIB-II

version published in RFC 1213 in May of 1991, contained some improvements, and

has proved that it can do a good job of meeting basic TCP/IP management needs.

MIB-II added many useful variables missing from MIB-I (Feit, 85). MIB files are

common variables used not only by SNMP, but CMIP as well.

In the late 1980's a project began, funded by governments, and large corporations.

Common Management Information Protocol (CMIP) was born. Many thought that

because of it's nearly infinite development budget, that it would quickly become in

widespread use, and overthrow SNMP from it's throne. Unfortunately, problems with

its implementation have delayed its use, and it is now only available in limited form

from developers themselves. (SNMP, Part 2 of 2, III.40.)

CMIP was designed to be better than SNMP in every way by repairing all flaws,

and expanding on what was good about it, making it a bigger and more detailed

network manager. It's design is similar to SNMP, where PDU's are used as variables

to monitor the network. CMIP however contains 11 types of PDU's (compared to

SNMP's 5). In CMIP, the variables are seen as very complex and sophisticated data

structures with three attributes. These include:

1) Variable attributes: which represent the variables characteristics (its data

type, whether it is writable)

2) variable behaviors: what actions of that variable can be triggered.

3) Notifications: the variable generates an event report whenever a specified

event occurs (eg. A terminal shutdown would cause a variable notification

event) (Comer, 82)

As a comparison, SNMP only employs variable properties from one and three above.

The biggest feature of the CMIP protocol is that its variables not only relay information

to and from the terminal (as in SNMP) , but they can also be used to perform tasks that

would be impossible under SNMP. For instance, if a terminal on a network cannot

reach the fileserver a pre-determined amount of times, then CMIP can notify

appropriate personnel of the event. With SNMP however, a user would have to

specifically tell it to keep track of unsuccessful attempts to reach the server, and then

what to do when that variable reaches a limit. CMIP therefore results in a more

efficient management system, and less work is required from the user to keep updated

on the status of the network. CMIP also contains the security measures left out by

SNMP. Because of the large development budget, when it becomes available, CMIP

will be widely used by the government, and the corporations that funded it.

After reading the above paragraph, you might wonder why, if CMIP is this

wonderful, is it not being used already? (after all, it had been in development for nearly

10 years) The answer is that possibly CMIP's only major disadvantage, is enough in

my opinion to render it useless. CMIP requires about ten times the system resources

that are needed for SNMP. In other words, very few systems in the world would able

to handle a full implementation on CMIP without undergoing massive network

modifications. This disadvantage has no inexpensive fix to it. For that reason, many

believe CMIP is doomed to fail. The other flaw in CMIP is that it is very difficult to

program. Its complex nature requires so many different variables that only a few

skilled programmers are able to use it to it's full potential.

Considering the above information, one can see that both management systems have

their advantages and disadvantages. However the deciding factor between the two,

lies with their implementation, for now, it is almost impossible to find a system with

the necessary resources to support the CMIP model, even though it is superior to

SNMP (v1 and v2) in both design and operation. Many people believe that the

growing power of modern systems will soon fit well with CMIP model, and might

result in it's widespread use, but I believe by the time that day comes, SNMP could

very well have adapted itself to become what CMIP currently offers, and more. As

we've seen with other products, once a technology achieves critical mass, and a

substantial installed base, it's quite difficult to convince users to rip it out and start

fresh with an new and unproven technology (Borsook, 48). It is then recommend that

SNMP be used in a situation where minimial security is needed, and SNMPv2 be used

where security is a high priority.

Works Cited

Borsook, Paulina. "SNMP tools evolving to meet critical LAN needs." Infoworld

June 1, 1992: 48-49.

Comer, Douglas E. Internetworking with TCP/IP New York: Prentice-Hall,

Inc., 1991.

Dryden, Partick. "Another view for SNMP." Computerworld December 11, 1995: 12.

Feit, Dr. Sidnie. SNMP. New York: McGraw-Hill Inc., 1995.

Fisher, Sharon. "Dueling Protocols." Byte March 1991: 183-190.

Horwitt, Elisabeth. "SNMP holds steady as network standard." Computerworld

June 1, 1992: 53-54.

Leon, Mark. "Advent creates Java tools for SNMP apps." Infoworld

March 25, 1996: 8.

Marshall, Rose. The Simple Book. New Jersey: Prentice Hall, 1994.

Miller, Mark A., P.E. Managing Internetworks with SNMP New York: M&T

Books, 1993.

Moore, Steve. "Committee takes another look at SNMP." Computerworld

January 16, 1995: 58.

Moore, Steve. "Users weigh benefits of DMI, SNMP." Computerworld

July, 31 1995: 60.

The SNMP Workshop & Panther Digital Corporation. SNMP FAQ Part 1 of 2.

Danbury, CT:

faq/part1/faq.html, [email protected]

The SNMP Workshop & Panther Digital Corporation. SNMP FAQ Part 2 of 2.

Danbury, CT:

faq/part2/faq.html, [email protected]

Stallings, William. SNMP, SNMPv2, and CMIP. Don Mills, Addison-Wesley, 1993.

Vallillee, Tyler, web page author. Http://www.undergrad.math.

VanderSluis, Kurt. "SNMP: Not so simple." MacUser October 1992: 237-240


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