The format for the standard HIPPI I-field (also referred to as CCI) that accompanies each connection request is shown in Figure A-1. The seven fields are described in Table A-1.
Table A-1. Fields of the HIPPI I-Field
Field | Bits | Description |
|---|---|---|
L | 31 | Local or Standard Format: 0=bits 30:0 of I-field conform to the usage described in this table 1=bits 30:0 are implemented in conformance to a private (locally-defined) protocol |
VU | 30:29 | Vendor Unique Bits: Vendors of end-system HIPPI equipment may use these bits for any purpose. Switches do not alter or interpret these bits. |
W | 28 | Width: 0=the data bus of the transmitting (source) HIPPI is 32 bits wide for 800 megabits/second 1=source's data bus is 64 bits wide for 1600 megabits/second |
D | 27 | Direction: 0=least significant bits of Routing Control field contain the next address for switch to use 1=most significant bits of Routing Control field contain the next address for switch to use |
PS | 26:25 | Path Selection: 00=source routing 01=Routing Control field contains logical addresses. Switch must select first route from a list of routes. 10=reserved 11=Routing Control field contains logical addresses. Switch selects route. |
C | 24 | Camp-on: 0=switch does not retry if connection is rejected 1=switch continues trying to establish a connection until the source aborts the connection request |
Routing | 23:0 | Routing Address: This field may contain source routing addresses or logical addresses, as indicated by the PS field. For source routing, the field contains a concatenated list of switch addresses that, when followed, lead to the destination. For logical addressing, the field contains two 12-bit addresses (destination and source) that are used by the intermediate switches to select a route from a table. |
Each HIPPI packet using the HIPPI Framing Protocol (HIPPI-FP) has a required 64-bit segment called the FP header, and two optional segments called D1 Area and D2 Area, as illustrated in Figure A-2. The D1 area is intended for communicating control (D1) information. It can also be used for padding out the first burst in order to position the user (D2) data in the second burst. The D2 area contains user/application data. The size of the D1 area is defined within the FP header. The size of the D2 area is not specifically defined, but is implicit due to the protocol definition. The D2 area consists of D2 data and possibly an offset and filler. The D2 offset and D2 data are defined in the FP header. The size of the filler can be calculated by rounding up to the next 64-bit word boundary, because the D2 area is required to be an integral number of 64-bit words.
The format for the HIPPI-FP packet is as shown in Figure A-2. The FP header consists of seven fields, shown in Figure A-3 and described in Table A-2.
Table A-2. Fields of FP Header
Field | Bits | Range of
Values | Description |
|---|---|---|---|
D2 Data Size | 63:32 | 0 - FFFFFFFF | Number of bytes of D2 data in this packet not counting the D2 offset nor the D2 fill. A size of FFFFFFFF (hexadecimal) indicates a packet of unknown, indeterminate, or “infinite” length. |
Dest ULP-id | 31:24 | 0 - FF | The upper layer identification number for the destination. |
P | 23 | 0 / 1 | Present: 0=there is no D1_Area in this packet 1=there is D1 data in the D1_Area of this packet |
B | 22 | 0 / 1 | Burst Boundary: 0=D2 data starts before beginning of second burst of this packet 1=D2 data starts at beginning of second burst of this packet |
Reserved | 21:11 | 000 | Must be zero. |
D1 Area Size | 10:3 | 0 - 7F | The number of 64-bit words in the D1 Area. The area does not necessarily contain valid D1 data; the area may be defined for padding purposes only. |
D2 Offset | 2:0 | 0 - 7 | The number of bytes between the last byte of the D1 Area and the first byte of D2 data. |