diff options
| author | Gerrit Renker <gerrit@erg.abdn.ac.uk> | 2008-09-04 07:30:19 +0200 |
|---|---|---|
| committer | Gerrit Renker <gerrit@erg.abdn.ac.uk> | 2008-09-04 07:45:33 +0200 |
| commit | 55ebe3ab2d504bd3f3eeade0262826210019abda (patch) | |
| tree | 6ccef1eb2aad025faa3e878cc0cc7666085e9852 /net/dccp/ackvec.h | |
| parent | 2faae5587f692fd5c79856ca4c4b90944ee0472a (diff) | |
dccp: Leave headroom for options when calculating the MPS
The Maximum Packet Size (MPS) is of interest for applications which want
to transfer data, so it is only relevant to the data transfer phase of a
connection (unless one wants to send data on the DCCP-Request, but that is
not considered here).
The strategy chosen to deal with this requirement is to leave room for only
such options that may appear on data packets.
A special consideration applies to Ack Vectors: this is purely guesswork,
since these can have any length between 3 and 1020 bytes. The strategy
chosen here is to subtract a configurable minimum, the value of 16 bytes
(2 bytes for type/length plus 14 Ack Vector cells) has been found by
experimentatation. If people experience this as too much or too little,
this could later be turned into a Kconfig option.
There are currently no CCID-specific header options which may appear on data
packets, hence it is not necessary to define a corresponding CCID field.
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Diffstat (limited to 'net/dccp/ackvec.h')
| -rw-r--r-- | net/dccp/ackvec.h | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/net/dccp/ackvec.h b/net/dccp/ackvec.h index 4ccee030524..1c10814fdf7 100644 --- a/net/dccp/ackvec.h +++ b/net/dccp/ackvec.h @@ -20,6 +20,9 @@ /* We can spread an ack vector across multiple options */ #define DCCP_MAX_ACKVEC_LEN (DCCP_SINGLE_OPT_MAXLEN * 2) +/* Estimated minimum average Ack Vector length - used for updating MPS */ +#define DCCPAV_MIN_OPTLEN 16 + #define DCCP_ACKVEC_STATE_RECEIVED 0 #define DCCP_ACKVEC_STATE_ECN_MARKED (1 << 6) #define DCCP_ACKVEC_STATE_NOT_RECEIVED (3 << 6) |