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# Direct Data Placement over Reliable Transports (iWARP-DDP)
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The Direct Data Placement protocol provides information to Place the incoming data directly into an upper layer protocol's receive buffer without intermediate buffers.
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## History
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This protocol has been defined in [RFC 5041](http://www.ietf.org/rfc/rfc5041.txt) in October 2007.
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## Protocol dependencies
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- [TCP](/TCP): Typically, iWARP-MPA uses [iWARP-MPA](/iWARP-MPA) on top of [TCP](/TCP) as its transport protocol.
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- [SCTP](/SCTP): iWARP-DDP can also run on top of [SCTP](/SCTP)
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## Example traffic
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Frame 10 (106 bytes on wire, 106 bytes captured)
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Arrival Time: Mar 26, 2008 18:13:03.752539000
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[Time delta from previous captured frame: 0.000043000 seconds]
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[Time delta from previous displayed frame: 0.000043000 seconds]
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[Time since reference or first frame: 0.000355000 seconds]
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Frame Number: 10
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Frame Length: 106 bytes
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Capture Length: 106 bytes
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[Frame is marked: False]
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[Protocols in frame: eth:ip:tcp:iwarp_mpa:iwarp_ddp_rdmap:data]
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[Coloring Rule Name: TCP]
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[Coloring Rule String: tcp]
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Ethernet II, Src: Ibm_8d:3c:cd (00:11:25:8d:3c:cd), Dst: Ibm_8d:3b:73 (00:11:25:8d:3b:73)
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Destination: Ibm_8d:3b:73 (00:11:25:8d:3b:73)
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Source: Ibm_8d:3c:cd (00:11:25:8d:3c:cd)
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Type: IP (0x0800)
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Internet Protocol, Src: 10.0.0.19 (10.0.0.19), Dst: 10.0.0.18 (10.0.0.18)
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Version: 4
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Header length: 20 bytes
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Differentiated Services Field: 0x00 (DSCP 0x00: Default; ECN: 0x00)
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Total Length: 92
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Identification: 0xbc5d (48221)
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Flags: 0x04 (Don't Fragment)
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Fragment offset: 0
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Time to live: 64
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Protocol: TCP (0x06)
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Header checksum: 0x6a1a [correct]
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Source: 10.0.0.19 (10.0.0.19)
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Destination: 10.0.0.18 (10.0.0.18)
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Transmission Control Protocol, Src Port: 35959 (35959), Dst Port: 4210 (4210), Seq: 28, Ack: 69, Len: 40
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Source port: 35959 (35959)
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Destination port: 4210 (4210)
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Sequence number: 28 (relative sequence number)
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[Next sequence number: 68 (relative sequence number)]
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Acknowledgement number: 69 (relative ack number)
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Header length: 32 bytes
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Flags: 0x18 (PSH, ACK)
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Window size: 5888 (scaled)
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Checksum: 0x1ae1 [correct]
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Options: (12 bytes)
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iWARP Marker Protocol data unit Aligned framing
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FPDU
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ULPDU length: 34 bytes
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CRC: 0x00000000
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iWARP Direct Data Placement and Remote Direct Memory Access Protocol
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DDP header
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DDP control field
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0... .... = Tagged flag: False
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.1.. .... = Last flag: True
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..00 00.. = Reserved: 0x00
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.... ..01 = DDP protocol version: 1
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Reserved for use by the ULP: 4300000000
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Untagged buffer model
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Queue number: 0
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Message sequence number: 1
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Message offset: 0
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RDMAP header
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Data (16 bytes)
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0000 00 04 00 00 01 00 00 00 00 b0 05 08 00 00 00 00 ................
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Data: 000400000100000000B0050800000000
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## Wireshark
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The iWARP-DDP dissector is fully functional. Since the headers of iWARP-RDMAP and iWARP-DDP overlap and since iWARP-DDP is in practice never seen without RDMAP on top, we have built a combined dissector that implements both protocols together as *iwarp\_ddp\_rdmap*. We discussed this with Guy Harris at the latest Sharkfest.
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We assume that it is running on top of [iWARP-MPA](/iWARP-MPA). [SCTP](/SCTP) support is not yet implemented since it is not used in practice. The following would have to be added for [SCTP](/SCTP) support:
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#define DDP_SEGMENT_CHUNK_ID 16
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#define DDP_STREAM_SESSION_CONTROL_ID 17
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static int
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dissect_ddp_segment_chunk(...)
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{
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/* dissection code for DDP segment chunk carried within SCTP */
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}
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static int
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dissect_ddp_stream_session_ctrl(...)
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{
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/* dissection code for DDP stream control carried within SCTP */
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}
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void
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proto_reg_handoff_iwarp_ddp_rdmap(voi)
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{
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dissector_handle_t seg_chunk_handle;
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dissector_handle_t str_ses_ctrl_handle;
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seg_chunk_handle = create_dissector_handle(dissect_ddp_segment_chunk, proto_iwarp_ddp_rdmap);
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str_ses_ctrl_handle = create_dissector_handle(dissect_ddp_stream_session_ctrl, proto_iwarp_ddp_rdmap);
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dissector_add("sctp.ppi", DDP_SEGMENT_CHUNK_ID, seg_chunk_handle);
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dissector_add("sctp.ppi", DDP_STREAM_SESSION_CONTROL_ID, str_ses_ctrl_handle);
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}
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## Preference Settings
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No preference settings.
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## Example capture file
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- [SampleCaptures/iwarp\_send\_recv.tar.gz](uploads/__moin_import__/attachments/SampleCaptures/iwarp_send_recv.tar.gz)
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- [SampleCaptures/iwarp\_rdma.tar.gz](uploads/__moin_import__/attachments/SampleCaptures/iwarp_rdma.tar.gz)
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## Display Filter
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A complete list of iWARP-DDP display filter fields can be found in the [display filter reference](http://www.wireshark.org/docs/dfref/i/iWARP-DDP.html)
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Show only the iWARP-DDP based traffic:
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```
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iwarp_ddp_rdmap
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```
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## Capture Filter
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You cannot directly filter iWARP-DDP protocols while capturing. However, if you know the [TCP](/TCP) port used (see above), you can filter on that one.
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## External links
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- [RFC 5041](http://www.ietf.org/rfc/rfc5041.txt) *Direct Data Placement over Reliable Transports*
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## Discussion
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---
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Imported from https://wiki.wireshark.org/iWARP-DDP on 2020-08-11 23:15:34 UTC |
