EL) also expresses itself in reduced data rates, since the bandwidth-delay-product bounds its throughput. For traffic of the highest priority the dominant contribution is head-of-line blocking time, namely the time a packet waits for draining of a packet whose transmission has already been commenced. Assuming a 150014 Byte packet just started transmission, a highest-priority packet needs to wait up to 1.7 ms (see Table 6.6.1). To determine the contribution to E2E latency, worst case single-switch times in Table 6.6.1 need to be multiplied by the number of switches traversed. It is, or course, possible to runt the outgoing packet (i.e. abruptly stop its transmission without computing a frame check sequence [FCS], and allowing the next switch to discard the errored frame), but this would require its full retransmission and burden the next switch along the path to parse and discard it. Table 6.6.1 Head-of-line blocking time versus line rate. Line rate head-of-line blocking time 10 Mbps 1.7 ms 100 Mbps 170 us 1 Gbps 17 us 10 Gbps 1.7 us 100 Gbps 0.17 us 14 2000 Bytes is the maximum Ethernet frame size (802.3as), however, jumbo frames of up to 9000 Bytes have also been standardized. 6.6 Transport Network A new mechanism that ameliorates head-of-line blocking is frame pre-emption, whereby express Ethernet frames (i.e. ones requiring expedited forwarding) can pre-empt the trans- mission of normal frames. Frame pre-emption along with interspersing express traffic (IET) are defined in IEEE 802.10 Qbu and 802.3br, respectively. Frame pre-emption occurs over a single link (i.e. fractional frames do not propagate through the network, but are re-assembled by the following switch), and thus requires compliant switches at both ends of the link. When an express frame arrives and a normal frame is being transmitted, the packet transmission of the normal frame is temporarily suspended, the neighboring switch buffers the content already received, the express frame(s) are sent and forwarded, transmission of the normal frame is conti