
\chapter{Network Management Protocols}
\label{nmp}\label{ch:nmp}

This chapter describes different existing standard protocols that are
used in network management.  SNMP (section~\ref{sec:snmp}) is widely
used in IP networks, and is also basis for some other protocols.
CMIP, described in section~\ref{sec:cmip} is an OSI\index{OSI} based protocol.
Network management protocols used in SS\#7 are described in
section~\ref{sec:css}, and network management for the ATM in
section~\ref{sec:atm}.


\section{Simple Network Management Protocol}
\label{sec:snmp}

\index{SNMP|textbf}  Simple Network Management Protocol (SNMP) is the most widely used management protocol in TCP/IP networks. This is due to it's simplicity, expandability, easy implementation and the fact that it poses only little stress on the managed network and the managed nodes~\cite{a5, a21}.

\index{SNMP!agent-manager concept} SNMP is based on a agent-manager concept, similar to the one illustrated in figure~\ref{fig:manageragent}: A manager sends requests to agents in network elements. The agents control Managed Objects (see page~\pageref{managedobjects}) accordingly, send responses and issue trap messages to the manager. The objects to be managed are defined in a MIB (see page~\pageref{mib})\index{MIB}. The requests and responses are exchanged using the User Datagram Protocol (UDP), which is a connectionless protocol. Trap-directed polling is used to decrease the management traffic on the network~\cite{a28}.

\index{SNMP!network management station (NMS)} The management functionality is centralized in a Network Management Station (NMS), which acts the manager role. Agents are kept simple, and thus SNMP is particularly conservative in the memory and computational requirements placed on devices connected to the network~\cite{a30}.

%SNMP is an asynchronous request/response protocol. This means that it does not have to wait for a response to a sent request before executing other tasks.


\subsection{SNMP Development}

The first version of SNMP, SNMPv1, became both an IETF (the Internet Engineering Task Force) and a de facto standard. This was due to it's widespread market acceptance. However, due to the lack of adequate security features, a new version of SNMP had to be developed. Various proposals on SNMPv2 were made, but none were adopted as a new standard. SNMPv2 failed because it had lost the simplicity of SNMPv1~\cite{a5, a36}.

Third version of SNMP, SNMPv3, is now in it's final stages of standardization. It builds on the first and the second versions of SNMP, and is intended to offer new capabilities for open, interoperable, and secure network management. It includes methods for security (authentication, encryption, privacy, authorization, and access control), and a new administrative framework (naming of entities, user names and key management, notification destinations, and proxy relationships, remotely configurable via SNMP operations)~\cite[pages~501--503]{a36}.


\subsection{SNMP Security}

The SNMP architecture makes a distinction between message security services (integrity, authentication and encryption) and access control services. Both message security and access control services can be provided by multiple security or access control models. The architecture allows coexistence of multiple models in order to allow future updates, in case the security requirements change or cryptographic protocols need to be replaced~\cite[pages 690--692]{b36}.

\index{SNMP!user-based security model (USM)} The User-based Security
Model (USM) provides integrity, authentication and privacy, and is the
standard security model currently used with SNMP version 3
(SNMPv3). The View-based Access Control Model (VACM)
\index{SNMP!view-based access control model (VACM)} provides checking
whether the users have proper access rights to access one or more
objects in a Management Information Base (MIB)\index{MIB} and perform
operations on these objects. USM is discussed in~\cite{rfc2274} and
VACM in~\cite{rfc2275}.


\section{Common Management Information Protocol}
\label{cmip}\label{sec:cmip}

\index{CMIP} Common Management Information Protocol (CMIP) is a much
more complicated and extensive network management protocol than
SNMP. It improves on many of SNMP's weaknesses, the security issues
for instance, thus providing a more efficient network management
environment. CMIP can also be used to perform tasks that would be
impossible under SNMP~\cite{a5}.

In CMIP, requests and responses between managers and agents (see
figure~\ref{fig:manageragent}) are exchanged using the OSI\index{OSI}
connection-oriented transport protocol that provides in-order,
guaranteed delivery~\cite{a28}.

CMIP also has some disadvantages: Due to it's complicity CMIP poses a lot of stress on the network and it's implementation is very difficult~\cite{a5}.


\section{Signalling System \#7}
\label{sec:css}

\index{SS\#7}\index{OMAP} Signalling System \#7 (SS\#7) Operations,
Maintenance and Administration Part (OMAP) offers a framework for
operation and maintenance in SS\#7 networks. OMAP uses principles of
management defined in TMN Recommendations (ITU-T\index{ISTU-T} M.3010 or ETSI ETR
037, see reference~\cite{a17}) and in OSI\index{OSI} Management
Recommendations of the ITU-T X.700-Series. Overview of OMAP and
Signalling System \#7 management is provided in ITU-T Recommendation
Q.750~\cite{a20}. 


\subsection{Management Layers}

The definition of TMN is concerned with five layers in management (see page~\pageref{tmnlayers}), namely business management, service management, network management, network element management, and elements in the network that are managed. Of these, OMAP provides the three lowest layers. It is not concerned with business management, and interacts with other TMN parts to provide service management~\cite{a20}.


\subsection{Management Functionality}

Management functions and resources provided by OMAP allow management within the SS\#7 signalling points. Three categories of management functionality (fault, configuration and performance management) of the five in OSI FCAPS\index{OSI!FCAPS}\index{FCAPS} model (see page~\pageref{fcaps}) are provided~\cite{a20}.

%The management functions are divided into three parts, which are~\cite{a20}:
%\begin{itemize}
%\item Management functions located in the Telecommunications Management Network (TMN, see page~\pageref{tmn}).


\section{ATM Network Management}
\label{sec:atm}

ATM Forum has standardised Broadband ISDN (B-ISDN)\index{B-ISDN}, and
defined also an ATM network management model.  This model is based on
TMN, and uses the lower three layers of the reference architecture of
ITU-T M.3010 (Network Management, Element Management, and Element
Layer)~\cite{a37}. The interfaces between layers are specified as
function points, and leave physical implementation unspecified.  ITU-T
has also used TMN as a basis in its ATM network management
standardisation~\cite{a38}. 

ATM Forum specifications define five managment intefaces: \textbf{M1}
between \textit{private network manager} and \textit{end user},
\textbf{M2} between \textit{private network manager} and
\textit{private network}, \textbf{M3} between \textit{private network
manager} and \textit{public network manager}, \textbf{M4} between
\textit{public network manager} and \textit{public network}, and
\textbf{M5} between two \textit{public network managers}.

In addition to M1-M5 network management, ATM-Forum provides a protocol called Interim Local Managment Interface (ILMI), which is a SNMP-based protocol~\cite{a40}.



