Two Non-IBA Service Types
General
In addition to the four IBA service types (RC, UC, RD, and UD), there are two non-IBA service classes and their respective QP types:
They are referred to as encapsulation services because they permit a non-IBA packet (e.g., Ethernet or an IP packet) to be encapsulated in (i.e., placed within) an IBA packet so it can be tunneled through the IBA fabric towards its destination. Note that either encapsulation method may be used to transport IPv6 datagrams.
Raw datagrams are similar to UD except that the source QP doesn't know the identity of the QP that will receive the message (i.e., the request packet does not contain a DestQP field).
Maximum Message Size
The maximum message size for either of these transport types is one PMTU (see “Maximum Data Payload Size” on page 42 for the definition of PMTU). The packet payload length must be divisible by four (it must be padded to ensure this).
LRH:LNH Defines Packet Type
Refer to Table 4-2 on page 74. IPv6 and Raw Ethertype datagrams are a special form of UD. The two-bit Link Next Header (LNH) field in the LRH defines the type of packet as one of the following:
An IBA packet.
A Raw packet (one of the following two types):
- An encapsulated IPv6 packet.
- An encapsulated EtherType packet.
| Packet Type | LNH bit 1 IBA Transport | LNH bit 0 GRH/IPv6 Header | Transport Type | Next Header After LRH Is |
|---|---|---|---|---|
| IBA Global | 1 | 1 | IBA | GRH |
| IBA Local | 1 | 0 | IBA | BTH |
| Encapsulated IP | 0 | 1 | Raw | IPv6 |
| Raw EtherType | 0 | 0 | Raw | RWH (EtherType) |
Encapsulated IPv6 Packet
The packet format for an encapsulated IPv6 packet is illustrated in Figure 4-2 on this page. In this case, the LRH field is immediately followed by an IPv6 header that identifies the packet payload as containing a transport or network protocol defined by the IETF (Internet Engineering Task Force) in the RFC 2460 document.
Figure 4-2. IPv6 Packet Format
Encapsulated EtherType Packet
The packet format for an encapsulated EtherType packet is illustrated in Figure 4-3 on this page. The LRH field is immediately followed by the Raw header (RWH), indicating that the packet payload contains a transport or network protocol not defined by the IETF. The usage of the EtherType field must conform to the definition in the IEEE Type Field Registrar (refer to the IEEE 802.3 standard, 1998 Clause 3.2.6 Length/Type Field specification; and the IEEE 802.1H-1995 standard). Encapsulated EtherType packets permit the transport of protocols not supported by the IPv6 format (e.g., TCP, UDP, and IPv4).
Figure 4-3. Encapsulated EtherType Packet Format
