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| author | Mat Martineau <mathewm@codeaurora.org> | 2010-08-05 15:54:27 -0700 |
|---|---|---|
| committer | Marcel Holtmann <marcel@holtmann.org> | 2010-08-10 07:59:11 -0400 |
| commit | db12d647ccc971ed120199dc7ea5be2b5887d328 (patch) | |
| tree | 6720ef2cbcd408fcca4c94b855970ca1e9908f3e | |
| parent | cff70fae111efba80c27023772ce5265797fb514 (diff) | |
| download | lwn-db12d647ccc971ed120199dc7ea5be2b5887d328.tar.gz lwn-db12d647ccc971ed120199dc7ea5be2b5887d328.zip | |
Bluetooth: Use 3-DH5 payload size for default ERTM max PDU size
The previous value of 672 for L2CAP_DEFAULT_MAX_PDU_SIZE is based on
the default L2CAP MTU. That default MTU is calculated from the size
of two DH5 packets, minus ACL and L2CAP b-frame header overhead.
ERTM is used with newer basebands that typically support larger 3-DH5
packets, and i-frames and s-frames have more header overhead. With
clean RF conditions, basebands will typically attempt to use 1021-byte
3-DH5 packets for maximum throughput. Adjusting for 2 bytes of ACL
headers plus 10 bytes of worst-case L2CAP headers yields 1009 bytes
of payload.
This PDU size imposes less overhead for header bytes and gives the
baseband the option to choose 3-DH5 packets, but is small enough for
ERTM traffic to interleave well with other L2CAP or SCO data.
672-byte payloads do not allow the most efficient over-the-air
packet choice, and cannot achieve maximum throughput over BR/EDR.
Signed-off-by: Mat Martineau <mathewm@codeaurora.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
| -rw-r--r-- | include/net/bluetooth/l2cap.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/include/net/bluetooth/l2cap.h b/include/net/bluetooth/l2cap.h index 16e412f3722b..6c241444f902 100644 --- a/include/net/bluetooth/l2cap.h +++ b/include/net/bluetooth/l2cap.h @@ -35,7 +35,7 @@ #define L2CAP_DEFAULT_MAX_TX 3 #define L2CAP_DEFAULT_RETRANS_TO 2000 /* 2 seconds */ #define L2CAP_DEFAULT_MONITOR_TO 12000 /* 12 seconds */ -#define L2CAP_DEFAULT_MAX_PDU_SIZE 672 +#define L2CAP_DEFAULT_MAX_PDU_SIZE 1009 /* Sized for 3-DH5 packet */ #define L2CAP_DEFAULT_ACK_TO 200 #define L2CAP_LOCAL_BUSY_TRIES 12 |