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Minor clarification on handling of fragmented packets #64

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Minor clarification on handling of fragmented packets #64

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f2e9dc5
Minor clarification on handling of fragmented packets
jafingerhut Feb 24, 2022
3f908e6
More proposed details on IP fragment handling.
jafingerhut Feb 24, 2022
9321641
Merge branch 'main' into minor-clarification-on-fragment-handling
jafingerhut Mar 1, 2022
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10 changes: 9 additions & 1 deletion documentation/general/design/dash-handling-fragmented-packets.md
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Expand Up @@ -123,9 +123,17 @@ The figure below shows the TCP header format. For more information, see [RFC 793
result in an **entry** into the **flow table** to **enable fast path
processing** for the duration of the connection.

1. If a subsequent packet arrives that is the start of a fragmented packet, the
1. If a subsequent packet arrives that is the first fragment of a fragmented packet (i.e. the Fragment Offset field is 0), the
**Frag ID** must be used to create a **new temporal flow** that can be
**uniquely identified** by the (**Frag ID**, **DST**, **SRC**, **Protocol ID**) tuple.
This **temporal flow** must record the relevant layer 4 header fields
from the packet that are needed for classification, e.g. source &
destination port, for retrieval by later arriving non-first IP
fragments that match this **temporal flow**.

1. If a packet arrives that is a non-first fragment (i.e. the Fragment Offset field is not 0), and there is not already a **temporal flow** that matches
this packet, the packet must be dropped, and no **temporal flow** will be
created.

1. The temporal flow should be **maintained until the last fragment arrives** or
the flow is **aged** or the connection is **closed**.
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