Linux Kernel AgentX sub-agents Linux Kernel AgentX Sub-Agents Oliver Wellnitz wellnitz@ibr.cs.tu-bs.de Institute of Operating Systems and Computer Networks Technical University Braunschweig, Germany Oliver Wellnitz, IBR, TU Braunschweig page 1/20 Diplomanden- und Doktorandenseminar, October 2002
� � � � Linux Kernel AgentX sub-agents Overview Network Managment (SNMP and AgentX) Motivation Linux Kernel Implementation Conclusions and Outlook Oliver Wellnitz, IBR, TU Braunschweig page 2/20 Diplomanden- und Doktorandenseminar, October 2002
� � � Linux Kernel AgentX sub-agents Why Network Management? Large computer networks cannot be managed manually Heterogeneous LANs Network management is essential Standard network managment protocol in the Internet: Simple network managment protocol (SNMP) Oliver Wellnitz, IBR, TU Braunschweig page 3/20 Diplomanden- und Doktorandenseminar, October 2002
� � � Linux Kernel AgentX sub-agents Simple Network Management Protocol SNMP contains three principal components: SNMP manager requests and processes information from SNMP agents SNMP agents on each device, provides management information to SNMP managers Management Information Bases (MIBs) define the data models of certain management areas, contain scalars and tables, MIB tree Oliver Wellnitz, IBR, TU Braunschweig page 4/20 Diplomanden- und Doktorandenseminar, October 2002
✂ ✂ � �✁ ✂ ✂ ✂ ✂ ✂ ✂ ✂ ✂ ✂ ✂ ✂ ✂ ✂ ✂ ✂ ✂ ✂ ✂ ✂ ✂ ✄ ✂ ✄ ✄ ✄ ✄ ✄ ✄ ✄ ✄ ✄ ✄ ✄ ✄ ✄ ✄ ✄ ✄ ✄ ✄ ✄ ✄ ✄ ✄ ✄ ✂ Linux Kernel AgentX sub-agents Simple Network Managment Protocol (cont.) SNMP manager Get/Set Get/Set Notification Notification Notification Get/Set Ether 10/100 100 COL 1 2 3 4 5 6 7 8 1 2 3 6 12 25 50 80 10 ! Power SNMP agents Oliver Wellnitz, IBR, TU Braunschweig page 5/20 Diplomanden- und Doktorandenseminar, October 2002
� � � Linux Kernel AgentX sub-agents Extensible Agents Goals Seperate SNMP protocol engine from MIB instrumentation Facilitate the (dynamic) extension with new MIB modules Extensible agents should be transparent for managers SNMP Agent Get / Set / Traps Subagent Get / Set SNMP SNMP SNMP Subagent Manager Master Agent Protocol Protocol Traps Get / Set / Traps Subagent Oliver Wellnitz, IBR, TU Braunschweig page 6/20 Diplomanden- und Doktorandenseminar, October 2002
� � � � Linux Kernel AgentX sub-agents Subagent Protocols SNMP multiplexing protocol (SMUX), RFC 1227, May 1991 SNMP distributed programm interface (DPI), RFC 1228, May 1991 Enhanced MANagement Agent Through Extensions (EMANATE), commercial product Agent eXtensibility (AgentX), RFC 2741, January 2000 Oliver Wellnitz, IBR, TU Braunschweig page 7/20 Diplomanden- und Doktorandenseminar, October 2002
� � � � � � � � Linux Kernel AgentX sub-agents AgentX Protocol Features Simplified variable enconding (SNMP uses ASN.1/BER) No authentication, no encryption ( simple to implement) Registration conflict arbitration Index allocation Multiple sessions with one connection Multiphase set operation Mature (First subagent protocol on IETF’s standards track) Oliver Wellnitz, IBR, TU Braunschweig page 8/20 Diplomanden- und Doktorandenseminar, October 2002
� � � � Linux Kernel AgentX sub-agents Motivation Problems of today’s userspace SNMP agents for Linux Various methods to gather information from the kernel ( ioctl , specific system call, /proc filesystem) Specific kernel interfaces may change SNMP Notifications are difficult to implement Functionality and management of kernel subsystem are split and often diverge Oliver Wellnitz, IBR, TU Braunschweig page 9/20 Diplomanden- und Doktorandenseminar, October 2002
Linux Kernel AgentX sub-agents Management Architecture Overview Userspace Kernel Userspace Userspace Kernel Kernel Subsystem Subsystem Subsystem Subsystem Mgmt Mgmt Mgmt Mgmt Info Info Info Info Kernel Kernel Userspace Userspace ... ... Subagent Subagent Subagent Subagent AgentX Module SNMP Master Agent Oliver Wellnitz, IBR, TU Braunschweig page 10/20 Diplomanden- und Doktorandenseminar, October 2002
Linux Kernel AgentX sub-agents Kernel AgentX Architecture Kernel subsystem MIB modules Kernel subsystem MIB / subsystem specific layer Notification Notification Callback Callback emitting emitting functions functions functions functions Session layer AgentX module SNMP AgentX protocol layer Master agent Receiving thread Socket layer Oliver Wellnitz, IBR, TU Braunschweig page 11/20 Diplomanden- und Doktorandenseminar, October 2002
� � � � � Linux Kernel AgentX sub-agents Subagent Registration Register MIB region Registration contains list of callback functions More than one registration is possible Callback functions handle all requests for a specific MIB subregion Asynchronous subagent registration does not depend on master agent Oliver Wellnitz, IBR, TU Braunschweig page 12/20 Diplomanden- und Doktorandenseminar, October 2002
� � � � Linux Kernel AgentX sub-agents Get / GetNext / GetBulk Processing Transfrom GetNext / GetBulk into (several) Get requests Subagent callback functions work on a single variable Split up large requests and reassemble responses (Multiplexing) Produce errors for requests that cannot be assigned to a subagent callback function Oliver Wellnitz, IBR, TU Braunschweig page 13/20 Diplomanden- und Doktorandenseminar, October 2002
Linux Kernel AgentX sub-agents Example: GetBulk processing SNMP Agent A A C Subagent C C 1 2 A B C SNMP SNMP AgentX Manager Master agent module B B Subagent Oliver Wellnitz, IBR, TU Braunschweig page 14/20 Diplomanden- und Doktorandenseminar, October 2002
� � � � Linux Kernel AgentX sub-agents Start Set Transaction TestSet Success Abort Transaction CommitSet UndoSet failed Success CleanupSet Transaction Transaction completed aborted Four different AgentX PDUs Multiphase set operation to maintain atomic nature of SNMP set requests (all-or-nothing) Multiplexing similar to Get/GetNext/GetBulk requests Stateless subagents; Undo data is stored within the AgentX module Oliver Wellnitz, IBR, TU Braunschweig page 15/20 Diplomanden- und Doktorandenseminar, October 2002
� � � � � � � � � � Linux Kernel AgentX sub-agents Implemented MIB Modules Interfaces MIB (IF-MIB, RFC 2863) module Read-only informational elements (ifname, speed, mtu, etc.) Can set interface up/down via ifAdminStatus Can send trap when interface status changes Standalone kernel module Linux Netfilter MIB module No exisiting MIB, developed our own (with Frank Strauß) Focuses on Netfilter core functions Can show / alter / add Netfilter rules Integrated in the Netfilter subsystem Oliver Wellnitz, IBR, TU Braunschweig page 16/20 Diplomanden- und Doktorandenseminar, October 2002
Linux Kernel AgentX sub-agents Conclusions Easy access to information from inside the kernel Can efficiently support SNMP notifications Kernel subsystem and management are integrated Requires little knowledge of SNMP or AgentX protocol No immediate information gain except for notifications Programming inside the kernel is more critical to machine stability Oliver Wellnitz, IBR, TU Braunschweig page 17/20 Diplomanden- und Doktorandenseminar, October 2002
� � � Linux Kernel AgentX sub-agents Outlook Not publicly released yet but planned to Get feedback from the network management and the Linux community Implement more Standard MIBs Oliver Wellnitz, IBR, TU Braunschweig page 18/20 Diplomanden- und Doktorandenseminar, October 2002
� Linux Kernel AgentX sub-agents Links Linux Kernel AgentX sub-agents, Diplomarbeit, September 2002 http://www.ibr.cs.tu-bs.de/ wellnitz/kagentxd/ The Simple Web http://www.simpleweb.org IETF AgentX Working Group http://www.scguild.com/agentx/ The NET-SNMP project http://www.net-snmp.org Oliver Wellnitz, IBR, TU Braunschweig page 19/20 Diplomanden- und Doktorandenseminar, October 2002
Linux Kernel AgentX sub-agents Thanks for listening. Questions? Comments? Oliver Wellnitz, IBR, TU Braunschweig page 20/20 Diplomanden- und Doktorandenseminar, October 2002
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