I'm reading RFC 7798, and I'm having trouble understanding the notation on some packet diagrams, such as figure 5,6 from 4.4.2, and figure 2 from 4.1, so far. To be specific, it is the ' : ' from the first mentioned and the '+=' notation from the latter what I don't understand. This is not a huge issue, but I was wondering if someone could give me some reference that defined the rules for these diagrams.
PS: I have already read RFC 2360 but they do not go into detail on this matter.

  • i would assume "...OPTIONAL RTP padding" means optionally insert padding up to 32 bits boundary, so that packet size is a multiple of 32 bits / 4 bytes
    – Effie
    Feb 16, 2022 at 16:35
  • some protocols require that packets align to the 4byte boundary and/or can use "length" fields which are given in number of 4 bytes, (e.g., ip header length).
    – Effie
    Feb 16, 2022 at 16:42

1 Answer 1


those are not notation but just ASCII art to render a schema in a text-only format.

For example the figure 2:

enter image description here

represents this:

enter image description here

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