Adding a hop by hop option to a packet incurs a two byte overhead, one for the option type and one for the option length. There is an additional 2 byte overhead to add the hop by hop header itself if it is not already present. The actual data of the packet will contain a set of control flags and an expiry timestamp. This will provide the features required for the processing and handling of delayed packets. The total size of the DTN hop by hop options including type and length details is 6 bytes. While other DTN systems include additional features within the DTN data format these would be best served by a separate extension header. Many of the additional features of the Bundle Protocol already have equivalent IP headers available to perform those functions such as the fragmentation header. Figure 2 shows how the new DTN header fits in with the existing IP headers.