1. 8: Network Management1 Network Management r introduction to network management m motivation m major components r Internet network management framework m MIB: management information base m SMI: data definition language m SNMP: protocol for network management m security and administration r presentation services: ASN.1 r firewalls

2. 8: Network Management2 What is network management? r autonomous systems (aka “network”): 100s or 1000s of interacting hw/sw components r other complex systems requiring monitoring, control: m jet airplane m nuclear power plant m others? "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."

3. 8: Network Management3 What would we like NM to do? r Detecting failures: NICs, routers, links r Monitor operations: m abnormal host behaviors m routing instabilities r Monitor traffic: supply stats for planning and resource allocation r Monitor performance contracts r Intrusion detection

4. 8: Network Management4 ISO NM model r Performance management r Fault management r Configuration management r Accounting management r Security management

5. 8: Network Management5 Infrastructure for network management agent data agent data agent data agent data managed device managing entity data network management protocol definitions: managed devices contain managed objects whose data is gathered into a Management Information Base (MIB) managing entity

6. 8: Network Management6 Network Management standards OSI CMIP r Common Management Information Protocol r designed 1980’s: the unifying net management standard r too slowly standardized SNMP: Simple Network Management Protocol r Internet roots (SGMP) r started simple r deployed, adopted rapidly r growth: size, complexity r currently: SNMP V3 r de facto network management standard

7. 8: Network Management7 SNMP overview: 4 key parts r Management information base (MIB): m distributed information store of network management data r Structure of Management Information (SMI): m data definition language for MIB objects r SNMP protocol m convey manager managed object info, commands r security, administration capabilities m major addition in SNMPv3

8. 8: Network Management8 SMI: data definition language Purpose: syntax, semantics of management data well- defined, unambiguous r base data types: m straightforward, boring r OBJECT-TYPE m data type, status, semantics of managed object r MODULE-IDENTITY m groups related objects into MIB module Basic Data Types INTEGER Integer32 Unsigned32 OCTET STRING OBJECT IDENTIFIED IPaddress Counter32 Counter64 Guage32 Tie Ticks Opaque

9. 8: Network Management9 SNMP MIB OBJECT TYPE: objects specified via SMI OBJECT-TYPE construct MIB module specified via SMI MODULE-IDENTITY (100 standardized MIBs, more vendor-specific) MODULE

10. 8: Network Management10 SMI: Object, module examples OBJECT-TYPE: ipInDelivers MODULE-IDENTITY: ipMIB ipInDelivers OBJECT TYPE SYNTAX Counter32 MAX-ACCESS read-only STATUS current DESCRIPTION “The total number of input datagrams successfully delivered to IP user- protocols (including ICMP)” ::= { ip 9} ipMIB MODULE-IDENTITY LAST-UPDATED “941101000Z” ORGANZATION “IETF SNPv2 Working Group” CONTACT-INFO “ Keith McCloghrie ……” DESCRIPTION “The MIB module for managing IP and ICMP implementations, but excluding their management of IP routes.” REVISION “019331000Z” ……… ::= {mib-2 48}

11. 8: Network Management11 OBJECT-TYPE examples udpInDatagrams OBJECT-TYPE SYNTAX Counter32 MAX-ACCESS read-only STATUS current DESCRIPTION "The total number of UDP datagrams delivered to UDP users." ::= { udp 1 } udpNoPorts OBJECT-TYPE SYNTAX Counter32 MAX-ACCESS read-only STATUS current DESCRIPTION "The total number of received UDP datagrams for which there was no application at the destination port." ::= { udp 2 }

12. 8: Network Management12 MIB example: UDP module Object ID Name Type Comments 1.3.6.1.2.1.7.1 UDPInDatagrams Counter32 total # datagrams delivered at this node 1.3.6.1.2.1.7.2 UDPNoPorts Counter32 # underliverable datagrams no app at portl 1.3.6.1.2.1.7.3 UDInErrors Counter32 # undeliverable datagrams all other reasons 1.3.6.1.2.1.7.4 UDPOutDatagrams Counter32 # datagrams sent 1.3.6.1.2.1.7.5 udpTable SEQUENCE one entry for each port in use by app, gives port # and IP address

13. 8: Network Management13 SNMP Naming question: how to name every possible standard object (protocol, data, more..) in every possible network standard?? answer: ISO Object Identifier tree: m hierarchical naming of all objects m each branchpoint has name, number 1.3.6.1.2.1.7.1 ISO ISO-ident. Org. US DoD Internet udpInDatagrams UDP MIB2 management

14. 8: Network Management14 Check out www.alvestrand.no/harald/objectid/top.html OSI Object Identifier Tree

15. 8: Network Management15 SNMP protocol Two ways to convey MIB info, commands: agent data Managed device managing entity response agent data Managed device managing entity trap msg request request/response mode trap mode

16. 8: Network Management16 SNMP protocol: message types GetRequest GetNextRequest GetBulkRequest Mgr-to-agent: “get me data” (instance,next in list, block) Message type Function InformRequest Mgr-to-Mgr: here’s MIB value SetRequest Mgr-to-agent: set MIB value Response Agent-to-mgr: value, response to Request Trap Agent-to-mgr: inform manager of exceptional event

17. 8: Network Management17 SNMP protocol: message formats

18. 8: Network Management18 SNMP security and administration r encryption: DES-encrypt SNMP message r authentication: compute, send MIC(m,k): compute hash (MIC) over message (m), secret shared key (k) r protection against playback: use nonce r view-based access control m SNMP entity maintains database of access rights, policies for various users m database itself accessible as managed object!

19. 8: Network Management19 The presentation problem Q: does perfect memory-to-memory copy solve “the communication problem”? A: not always! problem: different data format, storage conventions struct { char code; int x; } test; test.x = 259; test.code=‘a’ a 00000001 00000011 a 00000011 00000001 test.code test.x test.code test.x host 1 format host 2 format

20. 8: Network Management20 Solving the presentation problem 1. Translate local-host format to host-independent format 2. Transmit data in host-independent format 3. Translate host-independent format to remote-host format

21. 8: Network Management21 ASN.1: Abstract Syntax Notation 1 r ISO standard X.680 m used extensively in Internet m like eating vegetables, knowing this “good for you”! r defined data types, object constructors m like SMI r BER: Basic Encoding Rules m specify how ASN.1-defined data objects to be transmitted m each transmitted object has Type, Length, Value (TLV) encoding

22. 8: Network Management22 TLV Encoding Idea: transmitted data is self-identifying m T: data type, one of ASN.1-defined types m L: length of data in bytes m V: value of data, encoded according to ASN.1 standard 12345691234569 Boolean Integer Bitstring Octet string Null Object Identifier Real Tag Value Type

23. 8: Network Management23 TLV encoding: example Value, 5 octets (chars) Length, 5 bytes Type=4, octet string Value, 259 Length, 2 bytes Type=2, integer

24. 8: Network Management24 From Centralized to Distributed Monitoring Correction action Abnormality detection Discovery CentralizedHierarchicalDistributed

25. 8: Network Management25 Firewalls Two firewall types: m packet filter m application gateways To prevent denial of service attacks: m SYN flooding: attacker establishes many bogus TCP connections. Attacked host alloc’s TCP buffers for bogus connections, none left for “real” connections. To prevent illegal modification of internal data. m e.g., attacker replaces CIA’s homepage with something else To prevent intruders from obtaining secret info. isolates organization’s internal net from larger Internet, allowing some packets to pass, blocking others. firewall

26. 8: Network Management26 Packet Filtering r Internal network is connected to Internet through a router. r Router manufacturer provides options for filtering packets, based on: m source IP address m destination IP address m TCP/UDP source and destination port numbers m ICMP message type m TCP SYN and ACK bits r Example 1: block incoming and outgoing datagrams with IP protocol field = 17 and with either source or dest port = 23. m All incoming and outgoing UDP flows and telnet connections are blocked. r Example 2: Block inbound TCP segments with ACK=0. m Prevents external clients from making TCP connections with internal clients, but allows internal clients to connect to outside.

27. 8: Network Management27 Application gateways r Filters packets on application data as well as on IP/TCP/UDP fields. r Example: allow select internal users to telnet outside. host-to-gateway telnet session gateway-to-remote host telnet session application gateway router and filter 1. Require all telnet users to telnet through gateway. 2. For authorized users, gateway sets up telnet connection to dest host. Gateway relays data between 2 connections 3. Router filter blocks all telnet connections not originating from gateway.

28. 8: Network Management28 Limitations of firewalls and gateways r IP spoofing: router can’t know if data “really” comes from claimed source r If multiple app’s. need special treatment, each has own app. gateway. r Client software must know how to contact gateway. m e.g., must set IP address of proxy in Web browser r Filters often use all or nothing policy for UDP. r Tradeoff: degree of communication with outside world, level of security r Many highly protected sites still suffer from attacks.