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Enterprise Network Management Chapter 2 SNMPv3 and Network Management Jiun January 2005. SNMPv3 Structure. SNMPv3 entity consists of two main components: An SNMP engine A collection of SNMP applications. SNMPv3 Engine. The SNMPv3 engine is made up of four subcomponents:

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enterprise network management chapter 2 snmpv3 and network management jiun january 2005

Enterprise Network ManagementChapter 2SNMPv3 and Network ManagementJiunJanuary 2005

Chapter 2: SNMPv3 and Network Management

snmpv3 structure
SNMPv3 Structure
  • SNMPv3 entity consists of two main components:
    • An SNMP engine
    • A collection of SNMP applications

Chapter 2: SNMPv3 and Network Management

snmpv3 engine
SNMPv3 Engine
  • The SNMPv3 engine is made up of four subcomponents:
    • Dispatcher handles message sending and receiving.
    • Message subsystem handles message processing for SNMPv3, SNMPv2c, SNMPv1, and any other models.
    • Security subsystem handles security processing for SNMPv3 user-based security model (USM), SNMPv1/v2c community-based security model, and any additional (newly defined) models.
    • Access control subsystem handles the granting/rejecting of access to specific managed objects.

Chapter 2: SNMPv3 and Network Management

snmpv3 engine cont
SNMPv3 Engine (cont.)
  • Two important points to note about the engine subcomponents are that they:
    • Can hand off the message processing to each other as required.
    • Are themselves extensible entities.

Chapter 2: SNMPv3 and Network Management

a collection of snmp applications
A collection of SNMP applications
  • There are currently five SNMPv3 applications defined:
    • Command generators, create SNMP messages.
    • Command responders, respond to SNMP messages.
    • Notification originators, send trap or inform messages.
    • Notification receivers, receive and process trap or inform messages.
    • Proxy forwarders, forward messages between SNMP entity components.

Chapter 2: SNMPv3 and Network Management

snmpv3 message formats
SNMPv3 Message Formats
  • The message format is broken down into four overall sections made up of the following:
    • Common data: These fields occur in all SNMPv3 messages.
    • Security model data: This area has three subsections—one general, one for authentication, and one for privacy data.
    • Context: These two fields are used to provide the correct context in which the protocol data unit (PDU) should be processed.
    • PDU: This area contains an SNMPv2c PDU.

Chapter 2: SNMPv3 and Network Management

snmpv3 message formats cont
SNMPv3 Message Formats (cont.)

Figure 2-1. SNMPv3 message format.

Chapter 2: SNMPv3 and Network Management

snmpv3 message formats cont8
SNMPv3 Message Formats (cont.)
  • Common Data
    • MessageVersion
    • MessageID
    • MaxMessageSize
    • MessageFlags
    • MessageSecurity

Chapter 2: SNMPv3 and Network Management

snmpv3 message formats cont9
SNMPv3 Message Formats (cont.)
  • Security Model Data
    • General
      • EngineID
      • EngineBoots
      • EngineTime
      • UserName
    • Authentication Protocol
      • MD5 (Message Digest)
      • SHA (Secure Hash Algorithm)
    • Privacy Protocol
      • DES Key (Data Encryption Standard)

Chapter 2: SNMPv3 and Network Management

snmpv3 message formats cont10
SNMPv3 Message Formats (cont.)
  • Context
    • ContextName
    • ContextID
  • PDU
    • MessageFlags

Chapter 2: SNMPv3 and Network Management

snmpv3 message formats cont11
SNMPv3 Message Formats (cont.)
  • SNMPv3 Message Exchanges
    • SNMPv3 GetRequest
    • SNMPv3 Get-NextRequest
    • SNMPv3 GetBulkRequest
    • SNMPv3 SetRequest
    • SNMPv3 Notifications
    • Access Rights
    • Message Size
    • SNMPv3 Security

Figure 2-2. SNMP GetRequest and GetResponse messages.

Chapter 2: SNMPv3 and Network Management

snmpv3 message formats cont12
SNMPv3 Message Formats (cont.)
  • Problems with SNMP:
    • SNMP is not transaction-oriented but instead offers an all-or-nothing style of execution. It is difficult to manipulate very large data sets.
    • Scalability issues where tables grow to include thousands of rows.
    • Notifications are not guaranteed to arrive at their destination. Management operations (such as get or set) can time out if the network is congested or the agent host is heavily loaded.
    • SNMP messages use the UDP protocol (best-effort datagram service).

Chapter 2: SNMPv3 and Network Management

snmpv3 message formats cont13
SNMPv3 Message Formats (cont.)
  • The Different Versions of SNMP :
    • SNMPv1
    • SNMPv2c
    • SNMPv3

Chapter 2: SNMPv3 and Network Management

snmpv3 message formats cont14
SNMPv3 Message Formats (cont.)
  • SNMP Applications: MIB Browsers
    • MIB browsers are specialized tools used to examine the values of MIB object instances on a given agent. A MIB browser can be a fully integrated GUI-based application or a simple text-based one.

Chapter 2: SNMPv3 and Network Management

snmpv3 message formats cont15
SNMPv3 Message Formats (cont.)

A Closer Look at a MIB

  • The BEGIN keyword indicates the start of the MIB (arrow 1).
  • The IMPORTS keyword introduces descriptors from external MIBs in a similar way to #include in C and import in Java. The IMPORTS statement identifies the descriptor and the module in which it is defined (arrow 2).
  • The MODULE-IDENTITY keyword describes an entry point name for objects defined later in the MIB. The objects defined further down "hang" off this name (arrow 3), as shown by the black arrowed line.
  • The DESCRIPTION keyword provides details about the MIB content (arrow 4).
  • The REVISION keyword indicates the change history of the MIB (arrow 5).
  • The OBJECT IDENTIFIER keyword defines either new managed objects or placeholders for them in the MIB (arrow 6).
  • A sample, scalar, read-only integer object, mplsTunnelConfigured, is shown (arrow 7).
  • The remainder of the MIB (more scalars and tables) is skipped over (arrow 8).
  • The MIB finishes with the END keyword (arrow 9).

Figure 2-5. An extract from one of the draft-standard MPLS MIBs.

Chapter 2: SNMPv3 and Network Management

snmpv3 message formats cont16
SNMPv3 Message Formats (cont.)
  • Managed Objects:
    • Managed objects are the basic unit of exchange between an NMS and NEs. The managed objects are defined in the MIB and deployed in the network.

Chapter 2: SNMPv3 and Network Management

snmpv3 message formats cont17
SNMPv3 Message Formats (cont.)
  • There Is only One MIB :
    • One merit of a standard MIB is ease of extension. As new technologies are invented and deployed, the associated managed objects must be defined in new MIB modules. The latter can then be added to the standard MIB in an orderly fashion, e.g., by using enterprise-specific numbers.

Chapter 2: SNMPv3 and Network Management

snmpv3 message formats cont18
SNMPv3 Message Formats (cont.)
  • Analogy for an NMS:
    • In the case of operating systems, some of the abstract objects are:
      • Files
      • Applications
      • Processes
      • Devices, such as hard disks and network interfaces
      • Soft objects, such as print jobs and semaphores

Chapter 2: SNMPv3 and Network Management

snmpv3 message formats cont19
SNMPv3 Message Formats (cont.)
  • Analogy for an NMS (cont.):
    • NMS also employ the above objects in addition to other objects specific to network management:
      • MIB modules
      • Applications—agents and managers
      • Devices—remote NEs
      • Soft objects—connections, paths, interfaces, and so on

Chapter 2: SNMPv3 and Network Management

network elements
Network Elements

Figure 2-6. Typical NE software components. (in no particular order )

Chapter 2: SNMPv3 and Network Management

network elements cont
Network Elements (cont.)
  • An example of an NE is an intelligent line card, which is hosted inside another system, such as a PABX, ATM/MPLS switch, or IP router Command generators create SNMP messages.

Chapter 2: SNMPv3 and Network Management

network elements cont22
Network Elements (cont.)
  • Some characteristics of intelligent line cards include the following:
    • They can extend the lifespan of the host by adding advanced functions such as SNMP and VoIP for a PABX.
    • They can take a long time to develop.
    • Operators like to extract the maximum performance from them—for example, port bandwidth.
    • They increasingly incorporate numerous layer 1, 2, and 3 protocols.

Chapter 2: SNMPv3 and Network Management

network elements cont23
Network Elements (cont.)
  • High loading can occur when:
    • Many voice calls are in transit through a PABX.
    • Large numbers of ATM virtual circuits are transporting many ATM cells.
    • Large numbers of IP packets are in transit across a router.
    • Network topology changes result in routing protocol convergence.

Chapter 2: SNMPv3 and Network Management

introducing mpls first chunk
Introducing MPLS: First Chunk
  • On a more general note, a good understanding of MPLS is important for appreciating issues such as traffic engineering, network-QoS, and connection-oriented IP networks. Many voice calls are in transit through a PABX

Chapter 2: SNMPv3 and Network Management

the trend towards ip
The Trend Towards IP
  • Reasons for this migration towards IP:
    • IP has become the lingua franca of networking.
    • End-user devices, such as mobile phones, PDAs, and TV set-top boxes, have become IP-capable.
    • Existing layer 2 devices do not easily support massive (scalable) deployment of layer 3 protocols.
    • The need for specialized layer 2 maintenance skills is reduced.
    • A single layer 3 control plane is easier to manage.
    • Aggregation of IP traffic becomes possible, improving scalability.
    • Different (guaranteed) levels of network service can be sold to customers.
    • Management system object models can become more generic.

Chapter 2: SNMPv3 and Network Management

the trend towards ip cont
The Trend Towards IP (cont.)
  • MPLS is a good starting point for this migration because:
    • MPLS allows traffic engineering (putting the traffic where the bandwidth is).
    • MPLS integrates IP QoS with layer 2 QoS.
    • Many vendors are providing MPLS capability in their devices—for example, Cisco, Juniper, Nortel Networks, and Marconi.

Chapter 2: SNMPv3 and Network Management

mpls concepts
MPLS Concepts
  • MPLS is a forwarding technology. Its purpose is to receive an incoming traffic type (layer 2 or 3) at the network edge, encapsulate it, and then transmit it through an MPLS core (or cloud). At the exit from the cloud, another edge device removes the MPLS header and forwards the traffic towards its destination.

Chapter 2: SNMPv3 and Network Management

mpls concepts cont
MPLS Concepts (cont.)

Figure 2-7. An MPLS network joining enterprise branches.

Chapter 2: SNMPv3 and Network Management

mpls concepts cont29
MPLS Concepts (cont.)
  • Taking the first IP packet that arrives, LER1 can:
    • Forward the packet unlabeled; the packet is then routed to the next hop. In this mode, the MPLS nodes act as pure IP routers.
    • Drop the packet.
    • Encapsulate the packet with an MPLS label and push it onto an LSP.

Chapter 2: SNMPv3 and Network Management

mpls concepts cont30
MPLS Concepts (cont.)
  • An LSP has the following characteristics:
    • The LSP is created manually or via a signaling protocol.
    • The path taken by the LSP may be either user-specified or computed by LER1.
    • The LSP may have reserved resources, such as bandwidth, along the path.
    • There is a link between LER1 and LSR3, but the incoming traffic does not take this route. Instead, traffic at LER1 is pushed onto the LSP and follows the route LER1-LSR1-LSR2-LSR3.
    • IP traffic from IP Router 1 landing on LER1 is MPLS-encapsulated and forwarded across the LSP all the way to LER2. LER2 removes the MPLS encapsulation, carries out an IP lookup, and forwards the IP packet to IP Router 2.
    • Only two IP lookups are required in getting from IP Router 1 through the MPLS cloud to IP Router 2.
    • Once the IP traffic is MPLS-encapsulated, all subsequent routing is done using a label rather than any IP packet header-based addressing.
    • MPLS provides a QoS function.

Chapter 2: SNMPv3 and Network Management

mpls concepts cont31
MPLS Concepts (cont.)
  • Definition of an LSP
    • LSP is comprised of the following components on the originating LER:
      • A tunnel
      • A cross-connect
      • An out-segment
    • Each LSR in the core then supports the LSP by providing the following components:
      • An in-segment
      • A cross-connect
      • An out-segment
    • Finally, the terminating LER provides the endpoint for the LSP using the following components:
      • An in-segment
      • A cross-connect

Chapter 2: SNMPv3 and Network Management

summary
Summary
  • SNMPv3 provides several compelling advantages over previous versions.
  • MIB browsers represent an indispensable tool for both NMS software developers and network managers.
  • An NMS can also be arbitrarily complex with a great many components.
  • NEs are those components that combine together to make up a managed network.

Chapter 2: SNMPv3 and Network Management