On 7/25/16 6:25 AM, Brett Tate wrote:
Could you please provide us the boundary condition of
these SIP headers (TO, FROM, VIA).
Maximum length value allowed in these header.
RFC 3261 does not impose a maximum size upon headers. However, section
18.1.1 does discuss the message size constraints associated with some
transports. Additionally, some devices might want to impose some message
size limits to mitigate some forms of attack.
Concerning devices that attempt to impose header size constraints, the Via
header is one that occasionally causes interoperability issues until they
fix the device to accommodate larger headers. For instance with a default
Max-Forwards of 70 and use of a globally unique Via branch, there can be
many large comma-separated Via header field values within a single Via
header.
This question comes up regularly, and I have a standard response to it:
The length if any field within a sip message can be no longer than the
total message. This of course is obvious, but perhaps not always considered.
It is hard to process sip without at least buffering an entire message.
Once you have the message in a buffer, this also provides you with an
obvious way to manage individual fields without having lots of variable
width variables: simply reference fields in the message using offsets
and lengths within the message buffer.
If you assume some arbitrary maximum length for individual fields you
will likely eventually run into trouble. For instance, sip URIs *can*
get quite large in certain cases.
Good Luck,
Paul
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