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Chapter 8: Network Management

Chapter goals: introduction to network management motivation major components Internet network management framework MIB: management information base SMI: data definition language SNMP: protocol for network management security and administration presentation services: ASN.1 firewalls.

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Chapter 8: Network Management

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

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

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

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

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

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

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

  8. OBJECT-TYPE:ipInDelivers MODULE-IDENTITY:ipMIB SMI: Object, module examples 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} 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} 8: Network Management

  9. 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 8: Network Management

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

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

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

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

  14. SNMP protocol: message formats 8: Network Management

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

  16. a 00000011 00000001 a 00000001 00000011 The presentation problem Q: does perfect memory-to-memory copy solve “the communication problem”? A: not always! struct { char code; int x; } test; test.x = 256; test.code=‘a’ test.code test.x test.code test.x host 2 format host 1 format problem: different data format, storage conventions 8: Network Management

  17. 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 8: Network Management

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

  19. TLV Encoding Idea: transmitted data is self-identifying • T: data type, one of ASN.1-defined types • L: length of data in bytes • V: value of data, encoded according to ASN.1 standard Tag ValueType Boolean Integer Bitstring Octet string Null Object Identifier Real 1 2 3 4 5 6 9 8: Network Management

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

  21. Two firewall types: packet filter application gateways firewall Firewalls To prevent denial of service attacks: • 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. • 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. 8: Network Management

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

  23. Filters packets on application data as well as on IP/TCP/UDP fields. Example: allow select internal users to telnet outside. gateway-to-remote host telnet session host-to-gateway telnet session application gateway router and filter Application gateways 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. 8: Network Management

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

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