POSTECH DiffServ MIB Implementation

This homepage explains SNMP agent implementations for managing DiffServ routers, developed in DP&NM Lab, POSTECH, Korea. If you have any comments or questions on this page, please feel free to contact me at jay@postech.ac.kr.

Overview

• DiffServ manager/agent implementation in Linux DiffServ routers
• DiffServ MIB analysis
• Results from the research project funded by ETRI during nine months from 1999 to 2000.

Architecture

• The following figure explains our SNMP manager-agent implementation architecture.

  

DiffServ Router Configuration

• We have set up two DiffServ routers running on Linux machines. The followings are detail configuration of our DiffServ routers.

  CPU	Pentium III 450MHz
  RAM	128M
  Ethernet NIC	Intel 8825x-based PCI
  ATM NIC	ForeRunner PCA-200EPC
  Linux Kernel	2.3.40
  ATM patch	0.65
  IProute2	2.2.4-ss000305

• Linux kernel 2.3 includes DS-8 patch in it. Thus we don't need to download DS patch.
• For setting up ATM drivers, we have to install atm-0.65 package from http://icawww1.epfl.ch/linux-atm/
• The latest iproute2 package version is 2.2.4-ss001007 and can be downloaded from ftp://ftp.inr.ac.ru/ip-routing/. Though we have used ss000305 version of iproute2, we believe that our implementation will be compiled with the latest version of iproute2.

• When builing iproute2 binaries, iproute2/Config file needs to have the following configurations for DiffServ and ATM support.

  TC_CONFIG_DIFFSERV=y
  TC_CONFIG_ATM=y
  

• Now, we have a DiffServ router with two network interface cards, one is Ethernet and the other is ATM. iproute2 package contains 'tc', a traffic control utility for Linux. We can use tc for chaning kernel parameters via NetLink sockets for traffic shaping.

Documents for Linux DiffServ Implementation

• There are a few valuable documents to read before developing add-on packages on DiffServ router in Linux platform.

• Werner Almeswerger, "Linux Network Traffic Control - Implementation Overview," April 1999.
• Saravanan Radhakrishnan, "Linux - Advanced Networking Overview," Version 1, a technical report of the University of Kansas, September 1999.
• Gowri Dhandapani and Anupama Sundaresan, "Netlink Sockets - Overview," a technical report of the University of Kansas, October 1999.

IETF DiffServ MIB

• For managing DiffServ routers in the SNMP framework, the first thing to do is to define SNMP management information base for DiffServ routers. The IETF DiffServ working group first defined a DiffServ MIB on July 1999 and has exteded the MIB several times until now. The followings are some of IETF draft documents on DiffServ MIBs from verion 0 to version 8.

• draft-ietf-diffserv-mib-00.txt, July 1999
• draft-ietf-diffserv-mib-01.txt, October 1999
• draft-ietf-diffserv-mib-03.txt, May 2000
• draft-ietf-diffserv-mib-05.txt, November 2000
• draft-ietf-diffserv-mib-08.txt, February 2001

• As we can see here, the contents of DiffServ MIB are constantly chaning relatively too fast. When we develop a DiffServ agent, we need to fix one version of the MIB for concrete implementation. We have chosen diffserv-mib-03 for our implementation.
• First, we have analyzed diffserv-mib-03 to understand the structure and meaning of MIB objects. The following figure stands for the relationship of MIB tables in diffserv-mib-03. Each table is connected to other tables by following data path of packets.

  

• For monitoring statistics of DiffServ codepoint usages in DiffServ routers, there is another MIB defined by the IETF RMON working group. The MIB is an extension of RMON-2 MIB for monitoring statistics of DiffServ packets.

• draft-ietf-rmonmib-dsmon-mib-04.txt, January 2001

• We didn't implement DSMON MIB in our implementation. However, since the DiffServ MIB does not contain tables for statistics information, implementation of DSMON MIB is highly needed for complete management of DiffServ routers. In our implementation, we have added a proprietary table for storing statistic information in DiffServ MIB.

UCD-SNMP and DiffServ Agent Implementation

• Our SNMP agent for DiffServ MIB has been implemented by using UCD-SNMP package (now called as NET-SNMP). We have used UCD-SNMP 4.1.2 and the DiffServ MIB has been inserted as an extension MIB in UCD-SNMP agent.
• If you want to have more information of extending UCD-SNMP agent, you can find it at Dave Shield's contribution page.

• The detail implementation architecture of our SNMP agent is described in the following figure.

  

• Adding DiffServ MIB to UCD-SNMP agent is somewhat easy and straightforward. We have used 'mib2c' utility contained in UCD-SNMP package to convert DiffServ MIB text file to C templates.
• The difficult part is writing backend processing modules, depicted as a pink box in the figure, which map traffic shaping parameters from Linux kernel to MIB objects in the UCD-SNMP agent.
• For each SNMP operation on objects in DiffServ MIB, the UCD-SNMP agent invokes functions in the DiffServ agent. And then the DiffServ agent opens a netlink socket to the kernel and requests proper parameters for the SNMP operation. The retrieved parameters are mapped to one or more of SNMP MIB objects in the DiffServ MIB and transfers to the SNMP manager who initially requests the SNMP operation.

Agent Implementation Source Code

• In order to help people working on similar efforts and receive valuable feedbacks from them, we decided to release our source codes in public. We hope the source code should follow GNU General Public License so that the contribution thereafter can also belong to the open source community.

• Unfortunately, the current DiffServ agent implementation is operational, but not completely. Only some part of DiffServ MIB tables are supported. We're still working on it.

• Our source code package has the following files. The gzipped tar file (diffserv-postech-00.tar.gz) containing all is available for your convenience.
  • DIFF-SERV-MIB.txt : modified DiffServ MIB version-03
  • Makefile.agent : makefile for UCD-SNMP agent directory
  • Makefile.mibgroup : makefile for UCD-SNMP agent/mibgroup directory

  • diffServMib.h : global header file
  • diffServVariable.h
  • diffServMib.c : starting module of SNMP operation invocation
  • diffServAction.c
  • diffServAlgDrop.c
  • diffServClassifier.c
  • diffServCountAct.c
  • diffServDscpMarkAct.c
  • diffServMeter.c
  • diffServQ.c
  • diffServScheduler.c
  • diffServSixTupleClfr.c
  • diffServStatistics.c
  • diffServTBMeter.c

  • Linux/diffServLinux.h : Linux backend header file
  • Linux/diffServLinuxFunction.h
  • Linux/diffServLinux.c : Linux backend main module

Installation and Test Guide

• Download the following gzipped tar package containing all the source codes.
  diffserv-postech-00.tar.gz (35317 bytes)

• Before installing our codes, UCD-SNMP should be installed first. We've used UCD-SNMP 4.1.2 and assume it is compiled at /usr/local/ucd-inst/ucd-snmp-4.1.2 and installed at /usr/local/ucd-snmp. Caution! You should compile the UCD-SNMP package completely BEFORE installing our codes.

• Go to the agent/mibgroup directory and unpack our package there.

  $ cd /usr/local/ucd-inst/ucd-snmp-4.1.2/agent/mibgroup
  $ tar xf diffserv-postech-00.tar.gz
  

• The source codes will be placed at 'diffserv' directory.

• Copy DiffServ MIB file to UCD-SNMP MIB repository.

  $ cd diffserv
  $ cp DIFF-SERV-MIB.txt /usr/local/ucd-snmp/share/snmp/mibs
  

• Configure and compile the whole UCD-SNMP package with the following arguments. This will make SNMP agent with the DiffServ MIB extensions.

  $ cd /usr/local/ucd-inst/ucd-snmp-4.1.2
  $ configure --prefix=/usr/local/ucd-snmp --with-mib-modules="diffserv/diffServMib"
  $ make
  

• However, since we split DiffServ extensions into multiple source files, the agent should be rebuilt with modified makefiles. Move makefiles to proper directory as following instructions. Rename original makefiles if you want to keep them.

  $ cd /usr/local/ucd-inst/ucd-snmp-4.1.2/agent/mibgroup/diffserv
  $ cp Makefile.agent ../../Makefile
  $ cp Makefile.mibgroup ../Makefile
  

• The makefiles assume that iproute2 libraries are located at /usr/src/iproute2. Change the directory name if you install iproute2 at a different directory.

• Compile the UCD-SNMP agent only. You don't have to compile the whole package. What we want is the extended 'snmpd'.

  $ cd /usr/local/ucd-inst/ucd-snmp-4.1.2/agent
  $ make
  

• If the compilation finishes successfully, the newly-created agent binary can be found at /usr/local/ucd-inst/ucd-snmp-4.1.2/agent/snmpd. Of course, the agent supports DiffServ MIB objects we have just added.

• Kill any running snmpd if exists and execute the new agent binary with root privileges.

  # snmpd
  

• The DiffServ agent can be tested by sending SNMP GET message on any of DiffServ MIB objects under oid 1.3.6.1.2.1.1.12345.

  $ snmpget localhost public 12345.2.11.1.1.1
  12345.2.11.1.1.1 = 1
  

• If you have any GUI-based SNMP manager that can compile the DiffServ MIB, you can see easier interface like the following. Using MG-Soft MIB browser provides this running interface.

  

Feedbacks

• May 24, 2001 : About poptParseArgvString undefined symbol error, thanks to Banu Mohan (banu.mohan@windriver.com)

Comments and suggestions will be welcomed, please feel free to send mail to me!