Mobile IP Working Group Alessio Casati INTERNET DRAFT Lucent Technologies 10 March 2000 Charles E. Perkins Nokia Research Center Generic Tunneling Protocol (GTP) draft-casati-gtp-00.txt Status of This Memo This document is a submission by the mobile-ip Working Group of the Internet Engineering Task Force (IETF). Comments should be submitted to the MOBILE-IP@STANDARDS.NORTELNETWORKS.COM mailing list. Distribution of this memo is unlimited. This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. 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. Abstract Some discussion has been lately going on on the standardization of GRE within the IETF. GRE has an Impact on standard track protocols such as Mobile IP. A Generic Tunneling Protocol (GTP) sharing the same format and byte order of the 3GPP GTP protocol ( 3G TS 29.060) benefits from the commonality of the encapsulation format used in IP mobility support protocols in different families of 3G standards. 1. GTP HEADER The GTP header is a variable length header. It is used to encapulate packets over any network layer or transport layer protocol (e.g. it can be transported over UDP/IP, in which case it SHALL use port Casati,Perkins Expires 10 September 2000 [Page 1] Internet Draft GTP 10 March 2000 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Ver|*|*|*|S|R| Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tunnel Identifier | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sequence Number | Resv/Exp | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ number TBD [Note:-likely to be the 3386 port, currently allocated to GTP defined by 3GPP]). Two flags signal the presence of optional fields: the R flag and the S flag. The R flag is used to signal the need to interpret the Reserved/Experimental field. The S flag is used to signal the presence of the GTP Sequence Number field. If any of these flags are set, the length of the header is 12 octets and the fields corresponding to the flags that are set SHALL be evaluated by the receiver. The bits marked with '*' are currently unused and reserved for experimental use and they MUST not be interpreted. - The version field value is the version of the GTP protocol. This document specifies GTP version 1. - The type field defines possible different uses of the GTP. It shall be set to 0XFF when user traffic is transported. - The length Field defines the length of the GTP encapsulated packet (that is the length of the user datagram encasulated using the GTP protocol). - The Tunnel Identifier field is used as a multiplexing field. - The Sequence number field defines the value of the sequence number of the GTP encapsulated data. This field is present and SHALL be interpreted when the S Flag is set to 1. - The Resv/Exp field is present and SHALL be interpreted when the R flag is set to 1. Addresses The working group can be contacted via the current chairs: Casati,Perkins Expires 10 September 2000 [Page 2] Internet Draft GTP 10 March 2000 Basavaraj Patil Phil Roberts Nokia Corporation Motorola 6000 Connection Drive 1501 West Shure Drive M/S M8-540 Irving, TX 75039 Arlington Heights, IL 60004 USA USA Phone: +1 972-894-6709 Phone: +1 847-632-3148 Fax : +1 972-894-5349 EMail: Raj.Patil@nokia.com EMail: QA3445@email.mot.com Questions about this memo can also be directed to the authors: Alessio Casati CharlesCE.oPerkinsmmunications Systems Lab Lucent Technologies Sigma Building Nokia3Research1Center3 Fairchild Drive Windmill Hill Business Park Wiltshire, SN5 6P MountainUView,SCaliforniaA94043 United Kingdom email: acasati@lucent.com eMail:phcharliep@iprg.nokia.comone: +1-650 625-2986 phone: +44 179388 3861 Fax: +1 650 625-2502 Casati,Perkins Expires 10 September 2000 [Page 3]