Topology Discovery
Requirements
Loren Larsen
World Wide Packets
Scope
• Media supported
– Support all 802 media types
Basic Requirements
• Device Discovery
– IP Address
– Device type, model, software release
• Topology Discovery
– Device MAC Address
– Remote Port Id
– Handle Link Agg/PHY Redundancy
• VLAN Discovery
• Independent of Link Aggregation or xSTP
Device Discovery
• Current methods for IP Management Address
Discovery
– Notifications (traps) from DHCP Server (requires
DHCP Server hooks)
– NMS Pings an IP subnet range (extremely inefficient)
– Rely on traps to NMS from device (unreliable)
– NMS probes to router ARP caches and bridge tables for
MAC discovery
• Once IP Management discovered, type/version/SR
Release can be retrieved (no standard MIBs for
this)
Topology Discovery
• Current Methods
– Use 802.3ad LACP MIB to identify device
MAC of all neighboring devices (good
approach, standards based, doesn’t help with
other requirements) – assuming point-to-point
links
• Link Aggregation
– 802.3ad LACP MIB can be used to identify
aggregation groups.
Topology Discovery 2
• PHY Redundancy
• Solution must detect
both physical
connections
• Protocol packet could
report portId that is its
physical backup
VLAN Discovery
• It’s desirable to allow the VLAN topology.
• Port-based VLANs at a minimum
• Other VLAN types would be a nice bonus,
but probably much more complex.
Protocol
• Protocol should exchange information about
its neighbors
• Device stores information about the
neighbor on each port
• Neighbor information should age if not
refreshed
• Topology information can be retrieved from
each device via SNMP