Define network management.
"Network management includes the deployment, integration and coordination of the hardware, software, and human elements to monitor, test, poll, configure, analyze, evaluate, and control the network and element resources to meet the real-time, operational performance, and Quality of Service requirements at a reasonable cost."
Why does a network need management, like a jet airplane or a nuclear power plant?
An autonomous system ("network") has 1000s of interacting hardware/software components; such complex systems require monitoring, control.
What do managed devices contain?
Managed objects whose data is gathered into a Management Information Base (MIB); each managed device has an agent.
Name the parts of the network management infrastructure.
Managing entity; managed devices (with an agent and managed objects/MIB data); network management protocol between them.
OSI CMIP vs SNMP.
CMIP (Common Management Information Protocol): designed 1980's as the unifying net management standard; too slowly standardized. SNMP: Internet roots (SGMP); started simple; deployed, adopted rapidly; currently SNMP V3; de facto network management standard.
What are the 4 key parts of SNMP?
MIB (management information base); SMI (Structure of Management Information); SNMP protocol; security, administration capabilities.
What is the MIB?
A distributed information store of network management data.
What is SMI?
Structure of Management Information: the data definition language for MIB objects.
Which SNMP part was the major addition in SNMPv3?
Security, administration capabilities.
What is the purpose of SMI?
Syntax, semantics of management data well-defined, unambiguous.
OBJECT-TYPE vs MODULE-IDENTITY.
OBJECT-TYPE: data type, status, semantics of managed object. MODULE-IDENTITY: groups related objects into MIB module.
How are a MIB module and its objects specified?
The MIB module via SMI MODULE-IDENTITY (100 standardized MIBs, more vendor-specific); the objects via SMI OBJECT-TYPE construct.
ipInDelivers: SYNTAX, MAX-ACCESS and meaning.
SYNTAX Counter32; MAX-ACCESS read-only; "The total number of input datagrams successfully delivered to IP user-protocols (including ICMP)".
What is ipMIB, and what does it exclude?
A MODULE-IDENTITY: "The MIB module for managing IP and ICMP implementations, but excluding their management of IP routes."
UDP MIB module: what do UDPInDatagrams and UDPNoPorts count?
UDPInDatagrams: total # datagrams delivered at this node. UDPNoPorts: # undeliverable datagrams: no application at port. Both Counter32.
What is udpTable in the UDP MIB module?
A SEQUENCE: one entry for each port in use by app, gives port # and IP address.
How does SNMP name every possible standard object?
With the ISO Object Identifier tree: hierarchical naming of all objects; each branchpoint has name, number.
Which object is 1.3.6.1.2.1.7.1?
udpInDatagrams (path: ISO → ISO-ident. Org. → US DoD → Internet → management → MIB2 → UDP → udpInDatagrams).
What are the two ways SNMP conveys MIB info and commands?
Request/response mode (managing entity requests, agent responds) and trap mode (agent sends a trap msg to the managing entity).
Which SNMP messages go from manager to agent?
GetRequest, GetNextRequest, GetBulkRequest ("get me data": instance, next in list, block) and SetRequest (set MIB value).
Response vs Trap.
Both are agent-to-mgr. Response: value, response to Request. Trap: inform manager of exceptional event.
What is InformRequest?
Mgr-to-Mgr: here's MIB value.
Which fields are in the SNMP get/set header and in the trap header?
Get/set header: PDU type (0-3), Request ID, Error Status (0-5), Error Index. Trap header: PDU type 4, Enterprise, Agent Addr, Trap Type (0-7), Specific code, Time stamp.
List the four SNMP security and administration mechanisms.
Encryption: DES-encrypt SNMP message. Authentication: compute, send MIC(m,k). Protection against playback: use nonce. View-based access control: database of access rights, policies for various users.
What is MIC(m,k)?
A hash (MIC) computed over the message (m) and a secret shared key (k); it is computed and sent for authentication.
In view-based access control, what is special about the access-rights database?
The database itself is accessible as a managed object.