9.5 ICD X Cross Layer Signaling across the HAIPE
We have seen how MBRM and MBAC can work without assuming any information regarding the encrypted core network status. Now let us explore how the explicit congestion notification (ECN) bits, which are allowed to pass between the plain text IP layer and the cipher text IP layer (according to HAIPE standards 3.01 and later), can be utilized by the plain text resource management algorithms. The passing of these two bits can be considered as a form of cross layer signaling across the HAIPE. Other information allowed to pass through the HAIPE domain guard can also be utilized for resource management. This section focuses on utilizing of the ECN bits.
The IP header of a plain text IP layer packet, passing into HAIPE, has a one-byte type of service (TOS) field. Note that the HAIPE 3.0 and previous standards copy the left six bits of this TOS field from the plain text IP header onto the cipher text IP header TOS field (in order to allow using DiffServ QoS over the cipher text core). HAIPE 3.01 and subsequent standards allow the use of these two bits where the entire eight bits are copied from the plain text IP header to the cipher text IP header and vice versa.
Figure 9.19 shows a detailed view of the eight bits. The three leftmost bits define the CoS and we can refer to them as C1, C2, and C3. These three bits are used to define a CoS, such as voice, video, interactive data, streaming data, ftp, and so on. The next three bits are the precedence ...