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SNMP vs. CMIP
Ravneet Johal
Kamyar Partovi
CS 158B: Project
Friday, March 25, 2005
1. Introduction
Network management is essential to success for companies, especially during this era of the
information age. Exchanging information has become more efficient and has saved companies
time and money. Information exchange is done electronically and that means there is a need for
some type of network infrastructure. When there is a need for a network infrastructure, there is a
need for a network manager. When there is a need for a network manager, there is also a need
for interfaces and management systems that will help the network manager manage the
infrastructure. And when there is a need for interfaces and managements systems, there is a need
for protocols. This paper discusses two important protocols, which are Common Management
Information Protocol (CMIP) and Simple Network Management Protocol (SNMP). They are
both used widely for network management purposes. In this paper, first a broad overview of
both CMIP and SNMP are given. Then SNMP and CMIP are both compared and contrasted.
2. Common Management Information Protocol (CMIP)
Common Management Information Protocol (CMIP) is an interface for network management in
the Open Systems Interconnection (OSI) Reference Model. It was created around 1988 by the
Internet Activities Board (IAB), the department that was responsible for all Internet research and
development in the United States at the time (Burke 2004). Some large corporations invested
with the government on developing CMIP so that they can have the benefit of having a secure
and efficient network management protocol for themselves. CMIP is used with Common
Management Information Services Element (CMISE), which supports information exchange
between network management stations and management agents and also supports access to
managed information in the managed objects (Protocol Dictionary 2005). CMISE is a very
complicated protocol (and this is one of the reasons why CMIP is not widely used in networks
today). This network management protocol makes use of Remote Operations Service Element
(ROSE) to send and receive protocol data units (PDUs) (Burke 2004). Both CMIP and ROSE
are application layer protocols.
The protocol ROSE is an interface between all distributed applications and CMIP within the OSI
Reference Model. It is capable of providing remote operation capabilities, allows interaction
between entities within an application, and if a remote operations service was requested, it allows
the receiving entity to attempt the operation and report the results to the requesting entity
(Wikipedia 2001). Basically, CMIP passes the PDUs to ROSE so that the PDUs can be
distributed to the appropriate destination. CMIP and ROSE both reside in the Management
Process sector of the OSI Reference Model figure shown in Figure 1.
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3. Simple Network Management Protocol (SNMP)
In early 1988, when the need of a tool to manage a network such as the Internet was felt, the IAB
started to design concepts of the Simple Network Management Protocol (SNMP). The purpose
of designing SNMP was to make a basic network management device that can be applied simply
and easily. The Simple Network Management Protocol (SNMP), which is located in application
layer, is part of the Transmission Control Protocol / Internet Protocol (TCP/IP) network
architecture. SNMP is responsible for exchanging data between network devices. A network
administrator uses SNMP to manage network performance and to detect and fix any network
related problems.
SNMP has three important mechanisms, which are: managed devices, agents, and networkmanagement systems (NMSs). The managed device is responsible for colleting and storing data,
and these data are accessible to NMS by using SNMP. An agent is responsible for managing
data and translating them to a correct form that can be used. NMS implements the applications
that monitor managed devices.
According to Cisco System documentation, SNMP has several commands that are used for
managing devices and collecting the data. Those commands are read, write, trap and traversal
operation. The read command is used for monitor devices. The write command is used for
controlling devices. The trap command sends a report to NMS for any events that happen, and
traversal operations are responsible to decide what management device supports which variable.
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Security is a very important issue in SNMP because it does not have any verification ability, and
this matter caused SNMP to be open for a big security threats in high risk. These threats could be
modification of data and time and leaking the data.
4. Comparing CMIP and SNMP
What CMIP is to the OSI Reference Model is what SNMP is to the Transmission Control
Protocol/Internet Protocol (TCP/IP) network architecture (Burke 2004).
The Common Management Information Protocol (CMIP) uses the same Management
Information Base (MIB) that SNMP uses. The only difference is that there are more objects and
variables to comprehend and to work with. CMIP is more efficient and more detailed than
SNMPv1 and SNMPv2. So it is not a surprise that with more variables in the MIB that CMIP is
more detailed. Since CMIP is more detailed and has more functionality (which should be
considered a good thing), there is a tradeoff because CMIP takes up more system resources
(which is considered a bad thing). In CMIP, the variables or operations are seen as very complex
and sophisticated data structures, with many attributes (Tyler 2005). These include: operation
attributes, which represent the operation characteristics (its data type, whether it is writable);
operation behaviors, what actions of that operation can be triggered; and notifications, where the
operation generates an event report whenever a specified event occurs (eg. a terminal shutdown
would cause an operation notification event) (Tyler 2005). As a comparison, SNMP only
employs the operation attributes and the notifications (Trap messages) (Tyler 2005).
CMIP consists of 11 operations and SNMP only supports 5. The list of some of the CMIP
operations and what they do:
M-ACTION - requests an object to perform an action of some sort.
M-CANCEL-GET – cancels the previous M-GET command.
M-CREATE - creates specified objects.
M-DELETE - deletes specified objects.
M-EVENT-REPORT – when an event occurs, allows network agents to announce it.
M-GET - reads value of an object.
M-SET - adds, removes or replaces specified objects.
The other four operations that CMIP supports are M-Action-Confirmed, M-EventReportConfirmed, M-Set-Confirmed, and M-Linked-Reply. Most of these operations are confirmed
and that just means that they expect a reply back once they are sent.
Both SNMP and CMIP provide network management details to the network manager. They both
help the network manager solve problems. They both plan the capacity of the network and they
both also make reports for the network manager. Basically both of these protocols have the same
task: help the network manager manage his or her network.
Although the two network management protocols have the same goal, they take different paths to
attain that goal. One big difference between these protocols is the security. SNMP uses a
community name, which is not even encrypted. CMIP is used for its security, as it supports
authorization, access control, and security logs. In terms of data access, SNMP retrieves
individual items of information while CMIP retrieves a collection of information (Colorado St.
2005). Also, SNMP is more focused, while CMIP deals with classes of data that must be
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constrained (Colorado St. 2005). SNMP uses polling (where the management station asks the
management agents for status) and CMIP uses reporting, where a management agent reports to
the management station of its status (Colorado St. 2005). CMIP uses more space and system
resources than SNMP, which makes CMIP a more robust protocol. SNMP uses UDP datagrams
while CMIP uses connection-oriented sessions. Since CMIP seems to be more complicated and
robust at the same time, it seems just right to use CMIP in Wide Area Networks (WANs) and
SNMP in Local Area Networks (LANs). SNMP is widely used because of its simplicity. CMIP
has powerful capabilities with just one single request and it also provides better reporting of
unidentified network conditions. Even though Abstract Syntax Notation One (ASN.1) is used to
program CMIP (just like SNMP), it is still harder to program because of the complexity of the
functionality of the variables in CMIP. CMIP is object-oriented. This is analogous to high-level
programming languages (CMIP) and assembly language (SNMP).
5. Conclusion
In our opinion, SNMP and CMIP are different protocols that should not be compared. That is
because they do the same thing for different types of network infrastructures. SNMP and CMIP
are somewhat like two different religions. Religious people usually worship some type of God.
A person in a religion would try to attach itself to God by sacrificing (e.g. celibacy) or providing
services (e.g. help the poor). In our case, SNMP and CMIP (acting as the religious people in two
different religions) both try their best to attach themselves with the network manager (acting as
God) by providing services (such as remote operation of networks) and sacrifices (such as
security in SNMP and easy implementation in CMIP). SNMP would sacrifice security so that it
would be easier for the network manager to manage while CMIP would sacrifice the ease of
implementation just so that the network manager can do more things.
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6. Bibliography
CMIP (2001). Wikipedia. Retrieved March 22, 2005, from
http://en.wikipedia.org/wiki/Main_Page
Tyler. (unknown date). SNMP & CMIP. Tyler’s Homepage. Retrieved March 22, 2005, from
http://home.san.rr.com/tylerv/index.html
Network Management Notes. Retrieved by the March 22, 2005, from
http://csc.colstate.edu/summers/NetMan/note-435.htm
Burke, J. Richard (2004). Network Management Concepts and Practice: A Hands-on Approach.
New Jersey: Pearson Education, Inc.
CMIP. (unknown date). Protocol Dictionary. Retrieved March 22, 2005, from
http://www.javvin.com/protocolCMIP.html
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