Subject: Open issue 15: chunk with a too short length

From: Benoit Claise <[email-masked]>
Date: Wed, 21 Dec 2005 16:14:00 +0100

Dear all,

 From the Vancouver meeting minutes:

    Open Issue (not numbered): Chunk with too short length
    How to encode "chunk" with a too short length? Padding wouldn't be
    recognized
    by the collector. One solution would be using a new template for
    each length.
    Proposal: The protocol draft should say that padding MUST NOT be
    used for
    variable length IEs.

Here is a new proposed text (actually, only the second paragraph is new)

Basic Packet Report

For each selected packet, the Packet Report MUST contain the following 
information:
- The associationsId Information Element
- Some number of contiguous bytes from the start of the packet, 
including the packet header (which includes link layer, network layer 
and other encapsulation headers) and some subsequent bytes of the packet 
payload.  Alternatively, the number of contiguous bytes may start at the 
beginning of the payload. The Layer2PacketSection, 
l2PayloadPacketSection, mplsLabelStackSection, mplsPayloadPacketSection, 
ipPacketSection, and ipPayloadPacketSection PSAMP Information Elements 
are available for this use. 
- The input sequence number(s) of any Selectors that acted on the 
packet, represented by the selectorInputSequenceNumber Information Element.
 
The contiguous Information Elements (Layer2PacketSection, 
l2PayloadPacketSection, mplsLabelStackSection, mplsPayloadPacketSection, 
ipPacketSection, and ipPayloadPacketSection) MAY be encoded with a fixed 
length field or with a variable sized field. If one of these Information 
Elements is encoded with a fixed length field whose length is too long 
for the number of contiguous bytes in the selected packet, padding MUST 
NOT be used. In this case, the Exporting Process MUST export the 
information either in a new Template Record with the correct fixed 
length field, or either in a new Template Record with a variable length 
field.  

Feedback?

Regards, Benoit.

---

From: Benoit Claise <[email-masked]>
Date: Wed, 21 Dec 2005 23:55:25 +0100

BTW, regarding [PSAMP-INFO], the 2 ipHeaderPacketSection and 
ipPayloadPacketSection information element descriptions currently contain:

    "If insufficient octets are available,
    the remainder of the data should be zero-filled and an additional
    information element sent (e.g., ipPayloadLength) indicating how
    much of the data is valid."

Obviously these sentences will have to be removed.

Regards, Benoit.
> and other encapsulation headers) and some subsequent bytes of the 
> packet payload.  Alternatively, the number of contiguous bytes may 
> start at the beginning of the payload. The Layer2PacketSection, 
> l2PayloadPacketSection, mplsLabelStackSection, 
> mplsPayloadPacketSection, ipPacketSection, and ipPayloadPacketSection 
> PSAMP Information Elements are available for this use. 
> l2PayloadPacketSection, mplsLabelStackSection, 
> mplsPayloadPacketSection, ipPacketSection, and ipPayloadPacketSection) 
> MAY be encoded with a fixed length field or with a variable sized 
> field. If one of these Information Elements is encoded with a fixed 
> length field whose length is too long for the number of contiguous 
> bytes in the selected packet, padding MUST NOT be used. In this case, 
> the Exporting Process MUST export the information either in a new 
> Template Record with the correct fixed length field, or either in a 
> new Template Record with a variable length field.  
>
>
> Feedback?
>
> Regards, Benoit.
>