User`s guide

Introduction
1-31
Figure 1-12. Packet Headers With And Without Source-routing Bit Set
In TCP/IP hosts, an explorer packet exchange is normally
accomplished as part of the Address Resolution Protocol (ARP).
ARP is used to dynamically map IP addresses to MAC addresses.
The resulting source route is kept as part of the ARP cache.
The IP routing over source-routing feature allows the ATX to:
• Recognize Type-6 (IEEE 802) ARP packets, as well as Type-1
(Ethernet) ARPs.
• Recognize ARPs received with a null Routing Information Field
(RIF) even if the interface is not configured for source-routing.
• Cache the RIF on received ARP packets.
• Transmit ARP requests as source-routing explorer packets.
• Strip RIFs from received IP packets before processing by the IP
Router or the IP host.
• Attach the cached RIF to outbound IP packets when the RIF
exists as part of the ARP cache.
• Use the largest frame limit returned in the RIF as the Maximum
Transmission Unit (MTU) for the outbound packet.
destination source data
destination source dataRI
multicast bit=0 (not a source-routing packet)
multicast bit set (source-routing packet)