6.3.2 PROTOCOL WALK-THROUGH

The MIB is intended to cover both hosts and gateways, although there may be detailed differences in MIB application to the two cases. This section contains the appropriate interpretation of the MIB for hosts. It is likely that later versions of the MIB will include more entries for host management.

A managed host must implement the following groups of MIB object definitions: System, Interfaces, Address Translation, IP, ICMP, TCP, and UDP.

The following specific interpretations apply to hosts:

• ipInHdrErrors

  Note that the error "time-to-live exceeded" can occur in a host only when it is forwarding a source-routed datagram.

• ipOutNoRoutes

  This object counts datagrams discarded because no route can be found. This may happen in a host if all the default gateways in the host's configuration are down.

• ipFragOKs, ipFragFails, ipFragCreates

  A host that does not implement intentional fragmentation (see "Fragmentation" section of [INTRO:1]) MUST return the value zero for these three objects.

• icmpOutRedirects

  For a host, this object MUST always be zero, since hosts do not send Redirects.

• icmpOutAddrMaskReps

  For a host, this object MUST always be zero, unless the host is an authoritative source of address mask information.

• ipAddrTable

  For a host, the "IP Address Table" object is effectively a table of logical interfaces.

• ipRoutingTable

  For a host, the "IP Routing Table" object is effectively a combination of the host's Routing Cache and the static route table described in "Routing Outbound Datagrams" section of [INTRO:1].

  Within each ipRouteEntry, ipRouteMetric1...4 normally will have no meaning for a host and SHOULD always be -1, while ipRouteType will normally have the value "remote".

  If destinations on the connected network do not appear in the Route Cache (see "Routing Outbound Datagrams section of [INTRO:1]), there will be no entries with ipRouteType of "direct".

DISCUSSION:

The current MIB does not include Type-of-Service in an ipRouteEntry, but a future revision is expected to make this addition.

We also expect the MIB to be expanded to allow the remote management of applications (e.g., the ability to partially reconfigure mail systems). Network service applications such as mail systems should therefore be written with the "hooks" for remote management.