INTERNATIONAL TELECOMMUNICATION UNION COM 4 - LS 23 - E TELECOMMUNICATION STANDARDIZATION SECTOR STUDY PERIOD 2001-2004 Original: English Question(s): 18 5 - 14 February 2003 Ref. : TD 70 (Rev.2) (PLEN) Source: ITU-T Study Group 4 Title: Use of RFC 3430 LIAISON STATEMENT To: IETF Area Directors of Operations and Management (Bert Wijnen, Randy Bush) IETF email address for liaison statements Approval: SG 4 For: Action Deadline: October 2003 Contact: Lakshmi Raman SBC Communications USA Tel:+1 408 400 4149 Fax: +1 408 400 4101 Email: lraman@teraburst.com Based on email discussions with the Operations and Management Area Directors, we are incorporating a reference to RFC 3430 in the revision of Q.812 in progress. In addition, at the ITU-T Study Group 4 meeting in February 2003, we received a contribution on the implementation experience of running SNMP over TCP and SNMP over UDP. This experience may prove useful to the IETF in its evaluation of RFC3430 and its potential evolution. We would appreciate if the IETF make a similar call for implementation report of RFC 3430 and share the results with us. In response to the email suggestion from one of the Area Directors, we offer the following summary of one implementation experience. In the event the IETF does offer an official call at a later date, we would be pleased to provide any additional information required. In general, we would be grateful if you would keep us informed of your progress on this topic. Implementation Experience -------------------------- MII/BUPT TMN R&D Center (Beijing, China) has developed an SNMP (v2) over TCP implementation. The combined SNMP over TCP/UDP approach provided in this work is still under development. Workstations: one SNMP manager runs on a Sun Sparc Ultra2 WS, one SNMP agent runs on a Sun Sparc Ultra1 WS. Operation System: Sun Solaris 2.6 (Unix) Software platforms: some parts of SNMP(v2) PDU APIs are based on SNMP++, while the transport protocol control module, and the SNMP agent and manager toolkit are developed by MII/BUPT. The max SNMP message over UDP is allowed: 4096 Bytes The max SNMP message over TCP that is sent during test: 64K Bytes Network environment: The SNMP manager and the SNMP agent are located in separate workstations in different Ethernet LANs, which are connected via a radio network bridge. Both the manager and the agent are simulators, and no real network devices are actually managed by the manager or the agent during the experiments. MII/BUPT have compared the transfer efficiency for SNMP over TCP and SNMP over UDP. MII/BUPT captured all the packets between these two SNMP entities, and calculated the transfer efficiency for different sizes of SNMP messages to be transferred over the two different transport protocols. When no packet is lost, and the amount of data to be transferred is less than 64K, the SNMP over UDP is more efficient. Otherwise TCP is more efficient. Details can be provided if desired. Deltas from RFC3430 ------------------- The main part of the research is similar to what has been described in RFC 3430. But there are still some differences that may need consideration. 1) It was noticed that RFC 3430 does not provide a default policy for closing a TCP connection. One proposal for the default behaviour is that: The SNMP engine maintains a predefined number of TCP connections even if some of the connections have not been used for a period of time. The normal trigger point to close a connection is when a new connection establishment is requested, but no free resource is available for this connection. LRU(Least Recent Usage) is considered as the rule for closing inactive TCP connections. This proposal is also to avoid the extra costs for connection establishment. 2) A combined SNMP over TCP/UDP schema is proposed in the research. This requires that SNMP engine provides both SNMP over TCP and UDP implementations at the same time, and RFC 3430 also indicates this. The default policy used is for the originator to choose transport according to the size of the SNMP message. For both efficiency and convenience considerations, when an SNMP message is larger than a predefined size, then the SNMP engine chooses TCP as the transport protocol, otherwise it chooses UDP. (The predefined size is 4096 in the experiment, which is the max size allowed over UDP in the experiment, but this value may be adjusted.) This proposal tries to make use of the benefits of TCP and UDP in different situations. 3) The minimum for the size of an SNMP message over TCP defined in RFC 3430 seems relatively small. It is suggested that the SNMP over TCP engine should support the size of at least 64K or 32K bytes. The larger the size of an SNMP message is, the more benefit SNMP over TCP may provide.