Network Working Group J. Schoenwaelder, Editor Internet-Draft TU Braunschweig Expires December 1999 10 June 1999 SNMP-over-TCP Transport Mapping Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC 2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html Distribution of this document is unlimited. Please send comments to the Network Management Research Group, . Copyright Notice Copyright (C) The Internet Society (1999). All Rights Reserved. Abstract This memo defines a transport mapping for using the Simple Network Management Protocol (SNMP) over TCP. The transport mapping defined in this memo can be used with any version of SNMP. J. Schoenwaelder [Page 1] Internet-Draft SNMP-over-TCP Transport Mapping June 1999 Table of Contents 1 Introduction ................................................. 3 2 Definitions .................................................. 3 3 SNMP over TCP ................................................ 4 3.1 Serialization .............................................. 4 3.2 Well-Known Values .......................................... 4 3.3 Connection Management ...................................... 5 4 Acknowledgments .............................................. 5 5 References ................................................... 6 6 Editor's Address ............................................. 6 7 Full Copyright Statement ..................................... 7 J. Schoenwaelder [Page 2] Internet-Draft SNMP-over-TCP Transport Mapping June 1999 1. Introduction This memo defines a transport mapping for using the Simple Network Management Protocol (SNMP) over TCP. The transport mapping defined in this memo can be used with any version of SNMP. This document extends the transport mappings defined in RFC 1906 [1]. The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [2]. 2. Definitions IRTF-NMRG-SNMP-TM DEFINITIONS ::= BEGIN IMPORTS MODULE-IDENTITY, OBJECT-IDENTITY, experimental FROM SNMPv2-SMI TEXTUAL-CONVENTION FROM SNMPv2-TC; nmrgSnmpDomains MODULE-IDENTITY LAST-UPDATED "9906101100Z" ORGANIZATION "IRTF Network Management Research Group" CONTACT-INFO "Juergen Schoenwaelder TU Braunschweig Bueltenweg 74/75 38106 Braunschweig Germany Phone: +49 531 391-3283 Email: schoenw@ibr.cs.tu-bs.de" DESCRIPTION "This MIB module defines the SNMP-over-TCP transport mapping." ::= { experimental nmrg(91) 1 } -- SNMP over TCP over IPv4 snmpTCPDomain OBJECT-IDENTITY STATUS current DESCRIPTION "The SNMP-over-TCP-over-IPv4 transport domain. The corresponding transport address is of type SnmpTCPAddress." ::= { nmrgSnmpDomains 6 } -- matches first unused value -- below snmpDomains SnmpTCPAddress ::= TEXTUAL-CONVENTION DISPLAY-HINT "1d.1d.1d.1d/2d" J. Schoenwaelder [Page 3] Internet-Draft SNMP-over-TCP Transport Mapping June 1999 STATUS current DESCRIPTION "Represents a TCP/IPv4 address: octets contents encoding 1-4 IP-address network-byte order 5-6 TCP-port network-byte order " SYNTAX OCTET STRING (SIZE (6)) END 3. SNMP over TCP SNMP over TCP is an optional transport mapping. Implementors are encouraged to support SNMP over TCP whenever possible because this enables applications to make more efficient bulk transfers of MIB data [3]. The originator of a request/response transaction chooses the transport protocol for the entire transaction. The transport protocol MUST NOT change during a transaction. In general, originators of request/response transactions are free to use the transport they assume is the best in a given situation. However, as TCP has a larger footprint on resource usage than UDP, applications using SNMP over TCP may choose to switch back to UDP by refusing new TCP connections whenever necessary (e.g. too many open TCP connections). 3.1. Serialization Each instance of a message is serialized into a single BER-encoded message, using the algorithm specified in Section 8 of RFC 1906 [1]. The BER-encoded message is then sent over a TCP connection. It is possible to exchange multiple SNMP request/response pairs over a single (persistent) TCP connection. The length field in the BER- encoded SNMP message is used to separate multiple requests sent over a single TCP connection. 3.2. Well-Known Values It is RECOMMENDED that administrators configure their SNMP entities containing command generators to listen on TCP port 161 for incoming connections. It is also RECOMMENDED that SNMP entities containing notification receivers be configured to listen on TCP port 162 for J. Schoenwaelder [Page 4] Internet-Draft SNMP-over-TCP Transport Mapping June 1999 connection requests. When an SNMP entity uses the TCP transport mapping, it MUST be capable of accepting messages that are at least 8192 octets in size. Implementation of larger values is encouraged whenever possible. 3.3. Connection Management The use of TCP connections introduces costs. Connection establishment and teardown cause additional network traffic. Furthermore, maintaining open connections binds resources in the network layer of the underlying operating system. TCP connections are intended to be used when the size of the transferred data is large. If a connectionless transport were used instead, its small packet-size constraint would cause latency to increase excessively. Another advantage of using TCP connections, regardless of the message size, is that you do not need to implement retransmissions at the application level. This may result in simpler management applications. All SNMP entities (whether in an agent role or manager role) can close TCP connections at any point in time. This ensures that SNMP entities can control their resource usage and shut down TCP connections that are not used. SNMP engines SHOULD NOT process any outstanding requests if the underlying TCP connection has been closed. A `noResponse' error condition SHOULD be signalled for outstanding requests for command generator applications if the TCP connection is closed before a response has been received. 4. Acknowledgments The definitions in this memo are inspired by definitions found in RFC 1906 [1]. This document is the result of discussions of the Network Management Research Group (NMRG). Special thanks go to the following participants for their comments and contributions: Luca Deri, Jean-Philippe Martin-Flatin, Aiko Pras, Ron Sprenkels, Bert Wijnen. J. Schoenwaelder [Page 5] Internet-Draft SNMP-over-TCP Transport Mapping June 1999 5. References [1] Case, J., McCloghrie, K., Rose, M., and S. Waldbusser, "Transport Mappings for Version 2 of the Simple Network Management Protocol (SNMPv2)", RFC 1906, January 1996. [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [3] Sprenkels, R., and J.P. Martin-Flatin, "Bulk Transfers of MIB Data", The Simple Times, Vol. 7, No. 1, pp. 1-7, March 1999. 6. Editor's Address Juergen Schoenwaelder TU Braunschweig Bueltenweg 74/75 38106 Braunschweig Germany Phone: +49 531 391-3283 EMail: schoenw@ibr.cs.tu-bs.de J. Schoenwaelder [Page 6] Internet-Draft SNMP-over-TCP Transport Mapping June 1999 7. Full Copyright Statement Copyright (C) The Internet Society (1999). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. J. Schoenwaelder [Page 7]