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

This chapter describes different existing 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 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}

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}.

SNMP is based on a agent-manager concept\footnote{See
page~\pageref{manageragent}}, similar to the one illustrated in
figure~\ref{fig:manageragent} on page~\pageref{fig:manageragent}: A
manager sends requests to agents in network elements. The agents
control Managed Objects accordingly, send responses and issue trap
messages to the manager. The objects to be managed are defined in
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}.

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,
inter-operable, 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}.

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)
provides checking whether the users have proper access rights to
access one or more objects in a Management Information Base (MIB) and
perform operations on these objects. USM is discussed in~\cite{rfc2274} and
VACM in~\cite{rfc2275}.

\section{Common Management Information Protocol}
\label{sec: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
connection-oriented transport protocol that provides in-order,
guaranteed delivery~\cite{a28}.

CMIP also has some disadvantages: Due to it's complexity, 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}

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 M.3010 or ETSI ETR 037, see
reference~\cite{a17}) and in 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 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 standardized Broadband 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
standardization~\cite{a38}.

ATM-Forum specifications define five management interfaces:
\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 Management Interface (ILMI), which is a
SNMP-based protocol~\cite{a40}.
















