1. 21-07-0141-00-0000 IEEE 802.21 MEDIA INDEPENDENT HANDOVER DCN:21-07-0141-00-0000 Title: Data Type Encoding Date Submitted: April 27, 2007 Presented at IEEE 802.21 session #20 in Montreal Authors or Source(s): Yoshihiro Ohba, Subir Das, Yuu-Heng Alice Cheng, Miriam Tauil, Kenichi Taniuchi Abstract: This document describes problem with data type encoding in 802.21.

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3. 21-07-0141-00-0000 Issues Some value encoding rules for some TLVs are defined in IE definition (e.g., Link Type and QoS Parameters TLV values are defined in Section 6) and while others are defined in TLV definition in Section 8 There are a lot of duplicate value assignment in primitive definition and TLV definition (e.g, SupportMIHCommandList bitmap assignment in Sections 7 and 8) In Section 8.6, TLV type space is not unique across multiple messages This could make MIH protocol difficult to implement Requires 4 pieces of information (SID, Opcode, AID, TLV Type) to determine the actual “TLV Type” In Section 8.6, multiple TLVs in the same message point to the same TLV definition OldLinkIdentifer and NewLinkIdentifer in Section 8.6.2.8 point to Link Identifier TLV that has floating Type value assignment –Notation Problem Nested TLV encoding can be redundant E.g., Link Identifier encoding

4. 21-07-0141-00-0000 A Possible Approach Define data types and their encoding rule in a common place A general idea is to move Table 22 to a normative Annex with adding encoding rule. Define IEs, TLVs and primitives using the data types Advantage: Duplicate format definition can be avoided The specification can be more readable (detailed type definitions are not in the main sections)

5. 21-07-0141-00-0000 Data Type Table Example Data TypeDescriptionValid RangeEncoding Rule BITMAP(size)A bitmap of the specified size.…Each bit of a BITMAP(N) value [N=8*i, i=1, 2, …] is encoded as an N/8-octet value in order of significance. INTEGER(size)An integer of the specified size in number of octets. …Each octet of an INTEGER(N) value [N=1,2,..] is encoded in network-byte order into an N-octet field. LINK_TYPELINK_TYPE is derived form INTEGER(4) to represent a type of link …See Table X1 [currently Table 9] REVISIONREVISION is derived from BITMAP(64) to represent the release version of the standard. …See Table X1 [currently Table 9] LINK_IDA identifier of a link as defined by IEEE 802.21. Consisting of: 1) link type, and 2) MAC address of MN. …See Table X2 [see below] TRANSPORT ADDRESS……… ……… AttributeTypeDescription Link TypeLINK_TYPEType of the link. MN MAC AddressTRANSPORT_ADDRESSA Mobile Node’s MAC address of the link. Table X2: LINK_ID Parameters

6. 21-07-0141-00-0000 IE / TLV Value Definition Example General form: IE Example: Section 6.1.1 Network Type TLV Example: Section 8.5.9 Link Identifier Type=TYPE_IE_* or TYPE_TLV_*Length=length Value Name [DATATYPE] (Additional description) … Type=TYPE_IE_NETWORK_TYPELength=Variable Type [LINK_TYPE] Revision [REVISION] Type=TYPE_TLV_NETWORK_TYPELength=Variable Link Identifier [LINK_ID] Note that IE and TLV have different lengths in Type field.

7. 21-07-0141-00-0000 Primitive Definition Example General form: PRIMITIVE_NAME.{request,indication,response,confirm} ( ParameterName1 [DATATYPE] (mandatory/optional), ParameterName2 [DATATYPE] (mandatory/optional), … ) Note: Parameter table is not needed.

8. 21-07-0141-00-0000 TLV Type definition Example Type NameType ValueValue Type TYPE_TLV_LINK_ID1LINK_ID TYPE_TLV_OLD_LINK_ID2LINK_ID TYPE_TLV_NEW_LINK_ID3LINK_ID TYPE_TLV_MIH_EVENT_LIST4MIH_EVENT_LIST ………

9. 21-07-0141-00-0000 Discussion There may be three options to take: Option 1: Ignore this proposal Option 2: Adopt this proposal Option 3: Think about use of ASN.1