X.X Congestion Considerations

   The bandwidth resources used by RBridge Channel protocols are
   recommended to be small compared to the total bandwidth of the the
   links they traverse. When doing network planning, the bandwidth
   requirements for TRILL data, TRILL IS-IS, the TRILL ESADI protocol,
   RBridge Channel traffic, and any other link local traffic need to
   be taken into account.

   Specifications for particular RBridge Channel protocols MUST
   consider congestion and bandwidth usage implications and provide
   guidance on bandwidth or packet frequency management.  RBridge
   Channel protocols can have built-in bandwidth management in their
   protocols. Outgoing channel messages SHOULD be rate-limited, by
   configuring the underlying protocols or otherwise, to prevent
   aggressive connectivity verification or other applications
   consuming excessive bandwidth, causing congestion or becoming
   denial-of-service attacks.

   If these conditions cannot be followed, an adaptive loss-based
   scheme SHOULD be applied to congestion-control outgoing RBridge
   Channel traffic, so that it competes fairly, taking into account
   packet priorities and drop eligibility as indicated in the
   Inner.VLAN, with TCP or similar traffic within an order of
   magnitude.  One method of determining an acceptable bandwidth for
   RBridge Channel traffic is described in [RFC3448]; other methods
   exist.  For example, bandwidth or packet frequency management can
   include any of the following: a negotiation of transmission
   interval/rate such as that provided in BFD [RFC5880], a throttled
   transmission rate on "congestion detected" situations, a gradual
   ramp-up after shutdown due to congestion and until basic
   connectivity is verified, and other mechanisms.

   Connectivity chcking applications such as BFD [RFC5880] SHOULD be
   rate-limited to below 5% of the bit-rate of the associated link or
   links. For this purpose, the mean or sustained bit-rate of the link
   or links is used.

   Incoming RBridge Channel messages MAY be rate-limited as a
   protection against denial-of-service attacks.  This throttling of
   incoming messages SHOULD honor packet priorities and drop
   eligibility indications as indicate in the Inner.VLAN,
   preferentially discarding drop eligible and lower priority packets.