SNMP Simple Network Management Protocol Computer Science Essay

This research paper covers the simple web direction protocol constructs, its assorted versions with its advantages and drawbacks. I had discussed the three versions of SNMP and its characteristics followed by brief treatment of operation of SNMP in pull offing web with inside informations of its precursors. The basic message types used by SNMP are discussed in item like Get, GetNext, GetResponse, Set, and Trap or notify. The SNMPv2 is been developed to get the better of the Drawbacks of SNMPv1.The protocol of SNMPv2 is discussed followed with SNMPv3.

SNMPv3 is the latest one which improves upon both SNMP v1 and v2 by significantly adding to security.


The Simple Network Management Protocol ( SNMP ) is the standard operations & A ; care protocol for the Internet. SNMP based direction non merely produces direction solutions for systems, applications, complex devices, and environmental control systems, but besides provides the Internet direction solutions back uping Web services. SNMPv3, the most recent criterion approved by the Internet Engineering Task Force ( IETF ) adds unafraid capablenesss ( like encoding ) .

Simple Network Management Protocol ( SNMP ) is an application bed protocol that facilitates the exchange of direction information between web devices. SNMP enables web decision makers to pull off web public presentation, happen and work out web jobs and program for web growing. SNMP Facilitates the Exchange of Network Information between Devicess

Need of SNMP

Because there are a broad assortment of web elements that a NMS has to work with, a common protocol for pull offing these devices is indispensable. For illustration, a web may dwell of a mix of Windows and Linux waiters, routers from Cisco and other organisations etc. Network direction protocols provide a standardised method for hive awaying and accessing web direction information.

Precursors of SNMP

Some of the precursors to the current web direction protocols areSimple Gateway Monitoring Protocol ( SGMP ) ,High-Level Entity Management Systems ( HEMS ) andCommon Management Information Protocol ( CMIP ) .

SNMP Basic Message Types

SNMP is based on the manager-agent theoretical account where the director and agent communicate with each other through five basic message types.1 ) Get2 ) GetNext3 ) GetResponse4 ) Set5 ) Trap or adviseEven though there may be little fluctuations in the names of the messages ( for illustration, in some literature Trap is specified as Notify ) , the basic messages and their functionality remains basically the same.


The Get message allows the trough to acquire information for a specific variable. The MIB tabular array shops the information that the director needs.


Once the information from the managed device is received, if the director needs to read the following record, the GetNext message is used.


For either the Get or the GetNext, the agent responds with the GetResponse.


If the director wants to bespeak a alteration to be made for a specific variable, it uses a Set message. Once the alteration has been made, the agent responds with a GetResponse message if the alteration has been successfully made. If the alteration has non been successfully made, so an mistake indicant is sent.


A Trap is used when the agent sends unasked information to the direction station. This happens when an action is needed from the web director. For illustration, if a web component is on the brink of traveling down, the agent on the web component may direct a Trap message.

SNMP Basic Components

A SNMP managed web consists of three cardinal constituents:

Managed devices

A managed device is a piece of web equipment ( including its package ) that resides on a managed web.

A managed device might be a host, router, span, hub, pressman or modem. Managed device is a web node that contains an SNMP agent and that resides on a managed web. Managed devices collect and store direction information and do this information available to NMSs utilizing SNMP. Managed devices, sometimes called as web elements can be routers & A ; entree waiters, switches, Bridgess, hubs, computing machine hosts, or pressmans. Within a managed device, there may be several alleged managed objects. These managed objects are the existent pieces of hardware within the managed device ( for illustration, a web interface card ) , and the sets of constellation parametric quantities for the pieces of hardware and package ( for illustration, an intra-domain routing protocol such as RIP.


Agent is a web direction package faculty that resides in a managed device.

An agent has local cognition of direction information and translates that information into a signifier compatible with SNMP. Network Management Agent ( NMA ) is a resident procedure in each managed device. NMA is a procedure running in the managed device that communicates with the pull offing entity, taking local actions at the managed device under the bid and control of the pull offing entity.

Network-Management Systems ( NMSs )

A Network Management System ( NMS ) is a combination of hardware and package used to supervise and administrate a web. NMS executes applications that proctor and control managed devices.

Drawbacks of SNMPv1

In malice of being widely used, SNMP has some serious defects in security and information handling which are been discussed below1 ) SNMP uses clear text ( non encrypted ) for directing the community twine. The community twine is the “ watchword ” for communicating between the director and the agent. Because the community twine is in plaintext, it can be easy intercepted and security may be compromised.

2 ) SNMP works merely on IP webs. With the outgrowth of IP as the dominant protocol on the Internet, this may non be a serious job ; nevertheless, there may be other types of webs ( like Novell ‘s IPX/SPX ) that may necessitate monitoring and SNMP will non work on those webs.3 ) SNMP is inefficient when it has to recover a big dataset.4 ) SNMP is based on UDP. Because UDP is connectionless, it does non admit that messages have been received. In critical state of affairss, this may be debatable for web decision makers where they want to be perfectly certain that critical messages have in fact been delivered.

5 ) SNMP does non back up manager-to-manager communications. Therefore, one director does non cognize about the devices managed by another director. This may go debatable where a distributed web direction strategy is deployed.


SNMP Version 2 ( SNMPv2 ) is an development of the initial version SNMPv1. Originally, SNMP v2 was published as a set of proposed Internet criterions in 1993 ; presently, it is a Draft Standard. As with SNMPv1, SNMPv2 maps within the specifications of the Structure of Management Information ( SMI ) . In theory, SNMP v2 offers a figure of betterments to SNMPv1 including extra protocol operations.To take attention of these issues SNMP v2 is developed.These sweetenings include:Improved Structure of Management Information ( SMI )Support for New MIB ( Mgmt. Info.

Base ) objectsSupport for multiprotocol websManager-to-manager communicatingEnhanced securityEnhancement of the SMI includes adding newer informations types.For illustration, the maximal size of the whole numbers that SNMP can cover with is 232 – 1.SNMP v2 provides supports for whole numbers of this size but besides raises the maximal size of whole numbers that it can back up to 264 – 1.Increasing the size of the whole numbers allows the devices to keep much larger values, even though a larger memory may be needed. It besides differentiates between signed and unsigned whole numbers.SNMP v2 supports all five message types of SNMP ( like Get, GetNext etc.

) , but besides adds two new message types ;


GetBulkRequest allows the retrieval of a big set of informations in a individual petition, something that SNMP could non make. This reduces the clip for informations retrieval significantly. If the information set is excessively big to be sent in a individual spell, so the agent will direct every bit much informations as possible.

The director so needs to do another petition for the staying informations.


InformRequest is used for manager-to-manager communicating. One director can direct information to another director.

This allows hierarchal or distributed systems to pass on with each other.SNMP works merely on the IP protocol stack which makes it non functional on other webs. SNMP v2 is designed to work on IP, Appletalk, Novell IPX and OSI Connectionless Network Service ( CLNS ) .

SNMP v2 works precisely in the same manner in all these protocols. While the ability to work with multiple protocols is utile, peculiarly if legacy systems are present ; its importance may be decreasing because of the pervasiveness of IP based webs. The security of SNMP v2 is based on Secure SNMP ( S-SNMP ) .SNMP v2 provides both hallmark and encoding. Authentication, in the signifier of community strings is provided in SNMP but encoding is non. SNMP v2 uses a unafraid method of hallmark called the digest hallmark protocol. It authenticates a message ‘s beginning and the unity of the standard message. To accomplish this, the MD5 ( message digest 5 ) algorithm is used.


SNMP v3 improves upon both SNMP v1 and v2 by significantly adding to security. For illustration, in SNMP v1 and v2 no security was available for the Set messages. SNMP v3 is besides compatible with SNMP v1 and SNMP v2. Because SNMP v3 has a modular design which means it is non made up of a individual construction but assorted constituents that are integrated with one another. The primary advantage of that is if web directors required implementing merely portion of SNMPv3 they could make that without holding to implement the full SMNPv3 architecture.The edifice block of SNMPv3 architecture is the SNMP entity. Each entity, in bend is a aggregation of faculties that provide services and interact with each other.

Each entity can move as a director or an agent or both. The SNMP entity has two constituents, the SNMP Engine and Application ( s ) and is identified by the SNMP Engine ID. The applications work with the maps of the SNMP engine.

The faculties that make up SNMP entities communicate with each other through the abstract services interface.The abstract services interface has two constituents primitives and parametric quantities. A crude specifies the peculiar map to be performed while a parametric quantity is used for go throughing informations and control information. The bid generator initiates the SNMP bids, Get, Get Next etc. and processes the responses that are received as a consequence of those bids. The bid respondent processes the set and set petitions that come from a legitimate entity.After treating the petition it prepares a get-response message and sends it to the distant entity that made the petition. The presentment receiving system listens for presentment messages and generates a response when a message incorporating an Inform PDU is received.

It registers with the SNMP engine to have these messages. The presentment conceiver generates an inform message or a trap. It besides needs to happen out where to direct the message, which version of SNMP and what security parametric quantities will hold to be used. The proxy forwarder has a function similar to that of a proxy waiter.

The proxy forwarder grips messages generated by the bid generator, bid respondent, presentment generator and study index.Within the constituents of the SNMP Engine, the starter allows multiple versions of SNMP messages at the same time. It has three maps. It sends messages to and receives messages from the web. It determines the version of the message and finds out the corresponding message processing theoretical account and interacts with it.

Finally, it provides an abstract services interface to SNMP applications so that an entrance PDU is delivered to a local application every bit good as a PDU from a local application is delivered to a distant entity.The SNMP message processing subsystem prepares messages for directing and infusions informations from the messages received. It works with the starter for managing version specific SNMP messages. The security subsystem is used for hallmark and privateness protection.

This may incorporate multiple security theoretical accounts. The entree control subsystem provides mandate services so that applications can look into entree rights. This can be done for informations retrieval, alteration or for bring forthing presentments.


While many new MIB specifications have been given for SNMPv3, the nodes with the SNMP faculties are discussed here. This group includes seven new MIB groups. The basic SNMP direction architecture is given in the SNMP Framework MIB. SNMP MIB is used for the message processing and despatching subsystems. The snmpModules for applications has three groups: the mark MIB, the presentment MIB and the proxy MIB.

Security issues

As mentioned antecedently, one ground why SNMPv3 was developed is security. SNMPv3 addresses four types of web security issues. These are alteration of information, mask, alteration of the message watercourse and revelation. In alteration of the message watercourse, an unauthorised user might alter the information contents itself. The having terminal is incognizant that the information has been altered. Alteration does non change the transmitter ‘s or receiver ‘s reference. In mask, an unauthorised user sends information pretense to be an authorised user. The transmitter ‘s reference in this instance can be changed.

If person combines mask and alteration, so an altered message might be delivered and it would look that the message has come from an authorized beginning. Since SNMP uses UDP, which is a connectionless service, the packages consisting a message could take different waies. These packages can get out uneven order and they will hold to be put back in order.The interloper can reorder the message watercourse, thereby altering the order of the packages and the significance of the message.

Disclosure refers to the fact that the message may non be altered but person may listen in and decode the contents of the message between the director and an agent. SNMPv3 allows protection against these four types of security onslaughts. It does non protect against denial of service onslaughts and traffic analysis that may be performed by an unauthorised agent.To protect against four types of onslaughts mentioned, SNMPv3 has adopted a User Based Security Model ( USM ) . It serves two primary intents ; the first is to authenticate a message and the 2nd to code the message. The intent of hallmark is to do certain that the message beginning is echt and the intent of encoding is to do certain that the contents of the informations are protected.

The hallmark service has two primitives defined, one for the coevals of reliable outgoing messages and the other to formalize an attested entrance message. Similarly two primitives are defined for encoding, one to code outgoing messages and the other to decode incoming messages.Authentication is done either by the hash map MD5 or SHA-1. SNMPv3 provides seasonableness, thereby protecting against message hold or rematch. To protect against the revelation of the message it uses the cypher block chaining ( CBC ) manner of the DES encoding. A specific message format is besides defined that supports hallmark, seasonableness and privateness and lays out processs that can be used by one SNMP engine to obtain information from another SNMP engine. It besides lays out processs for the coevals of keys, its update and usage.

SNMPv3 besides provides entree control which trades with who can entree the web constituents and what they have entree to. In SNMPv1 and v2 this was done by a community based entree policy. SNMPv3 provides a more secure and flexible attack to entree control known as View-based Access Control theoretical account ( VACM ) .

VACM has made up of five elements. These are:GroupsSecurity LevelContextMIB positionsEntree Policy


A group is identified by a group name. A group is defined by the combination of a security theoretical account and a security name. The security name represents a prinicipal.

The principal is a individual or application bespeaking a service. All the elements belonging to certain group have the same entree rights.

Security Level

This provides the degree of security for the message that contains the petition.

For illustration, read entree might be allowed but non write entree.


A SNMP context is a aggregation of direction information that can be accessed by the SNMP entity. Each SNMP entity can hold entree to more than one context.

MIB Positions

Sometimes entree of a peculiar group has to be restricted to merely a subset of the objects managed by the agents. A MIB position of the group defines the subset. The MIB position can be defined as a aggregation of subtree. A peculiar subtree can be included or excluded from the position. A subtree is defined as a node in the MIB, with all its subsidiary elements.

Entree Policy

Entree policy determines the entree rights to objects. The rights can be, for illustration, read-view, write-view and notify-view. The get-request, get-next-request, and get-bulk-request operations use the read-view.

Set-request uses write-view. Notify-view is the group of object cases authorized for presentment. The entree rights given depend on many factors, like the principal doing the petition, , the security degree, the security theoretical account being used, the MIB context, the object case and the type of entree requested.The VACM MIB is where the information that VACM needs is stored. The vacmContextTable gives the locally available contexts. The vacmSecurityToGroupTable has a groupName, securityModel and securityName. The groupName gives the list of principals that operate under a security theoretical account. The vacmAccessTable is configured for specifying entree rights to groups.

Access rights can be defined for one or more contexts, security theoretical accounts or security degrees. The vacmAcessTable plants with the vacmContextTable to find the locally available contexts. The vacmAccessTable has two constituents, the vacmViewSpinLock and the vacmViewTreeFamilyAcessTable. The spin lock is used by the SNMP bid generator application for organizing the usage of set operation in making or modifying positions. The usage of the spin lock is optional.

The vacmViewTreeFamilyTable describes the household of subtrees available in the MIB positions in the local SNMP agent for each context.


Presently, there are three versions of SNMP defined and the overview of operations and characteristics of assorted versions of SNMP v1, A SNMP v2 andA SNMP v3 are discussed below.


Basic Operations and Features

Get – Get message used by the NMS to recover the value of one or more object cases from an agent.GetNext – GetNext message is used by the NMS to recover the value of the following object case in a tabular array or a list within an agent.Set – Set message used by the NMS to put the values of object cases within an agent.Trap – Trap message used by agents to asynchronously inform the NMS of a important event.SNMP v2 covers Additional Operations and FeaturesGetBulk – GetBulk is used by the NMS to expeditiously recover big blocks of informations.Inform – Allows one NMS to direct trap information to another NMS and to so have a response.SNMP v3 covers the Security EnhancementUser-based Security Model ( USM ) for SNMP message security.View-based Access Control Model ( VACM ) for entree control.Dynamically configure the SNMP agents utilizing SNMP SET bids.