messages. Optionally, the BGP FSM can support
additional interaction with the TCP connection
negotiation. The interaction with the TCP events
may increase the amount of logging the BGP peer
connection requires and the number of BGP FSM
changes.
Value: TRUE or FALSE
Group 4: BGP Message Processing
Optional Session Attributes: DelayOpen, DelayOpenTime,
DelayOpenTimer,
SendNOTIFICATIONwithoutOPEN,
CollisionDetectEstablishedState
Option 1: DelayOpen
Description: The DelayOpen optional session attribute allows
implementations to be configured to delay sending
an OPEN message for a specific time period
(DelayOpenTime). The delay allows the remote BGP
Peer time to send the first OPEN message.
Value: TRUE or FALSE
Option 2: DelayOpenTime
Description: The DelayOpenTime is the initial value set in the
DelayOpenTimer.
Value: Time in seconds
Option 3: DelayOpenTimer
Description: The DelayOpenTimer optional session attribute is
used to delay the sending of an OPEN message on a
connection. The DelayOpenTimer_Expires event
(Event 12) is described in Section 8.1.3.
Value: Time in seconds
Option 4: SendNOTIFICATIONwithoutOPEN
Description: The SendNOTIFICATIONwithoutOPEN allows a peer to
send a NOTIFICATION without first sending an OPEN
message. Without this optional session attribute,
the BGP connection assumes that an OPEN message
must be sent by a peer prior to the peer sending a
NOTIFICATION message.
Value: True or False
Option 5: CollisionDetectEstablishedState
Description: Normally, a Detect Collision (see Section 6.8)
will be ignored in the Established state. This
optional session attribute indicates that this BGP
connection processes collisions in the Established
state.
Value: True or False
Note: The optional session attributes clarify the BGP FSM
description for existing features of BGP implementations.
The optional session attributes may be pre-defined for an
implementation and not readable via management interfaces
for existing correct implementations. As newer BGP MIBs
(version 2 and beyond) are supported, these fields will be
accessible via a management interface.
8.1.2. Administrative Events
An administrative event is an event in which the operator interface
and BGP Policy engine signal the BGP-finite state machine to start or
stop the BGP state machine. The basic start and stop indications are
augmented by optional connection attributes that signal a certain
type of start or stop mechanism to the BGP FSM. An example of this
combination is Event 5, AutomaticStart_with_PassiveTcpEstablishment.
With this event, the BGP implementation signals to the BGP FSM that
the implementation is using an Automatic Start with the option to use
a Passive TCP Establishment. The Passive TCP establishment signals
that this BGP FSM will wait for the remote side to start the TCP
establishment.
Note that only Event 1 (ManualStart) and Event 2 (ManualStop) are
mandatory administrative events. All other administrative events are
optional (Events 3-8). Each event below has a name, definition,
status (mandatory or optional), and the optional session attributes
that SHOULD be set at each stage. When generating Event 1 through
Event 8 for the BGP FSM, the conditions specified in the "Optional
Attribute Status" section are verified. If any of these conditions
are not satisfied, then the local system should log an FSM error.
The settings of optional session attributes may be implicit in some
implementations, and therefore may not be set explicitly by an
external operator action. Section 8.2.1.5 describes these implicit
settings of the optional session attributes. The administrative
states described below may also be implicit in some implementations
and not directly configurable by an external operator.
Event 1: ManualStart
Definition: Local system administrator manually starts the peer
connection.
Status: Mandatory
Optional
Attribute
Status: The PassiveTcpEstablishment attribute SHOULD be set
to FALSE.
Event 2: ManualStop
Definition: Local system administrator manually stops the peer
connection.
Status: Mandatory
Optional
Attribute
Status: No interaction with any optional attributes.
Event 3: AutomaticStart
Definition: Local system automatically starts the BGP
connection.
Status: Optional, depending on local system
Optional
Attribute
Status: 1) The AllowAutomaticStart attribute SHOULD be set
to TRUE if this event occurs.
2) If the PassiveTcpEstablishment optional session
attribute is supported, it SHOULD be set to
FALSE.
3) If the DampPeerOscillations is supported, it
SHOULD be set to FALSE when this event occurs.
Event 4: ManualStart_with_PassiveTcpEstablishment
Definition: Local system administrator manually starts the peer
connection, but has PassiveTcpEstablishment
enabled. The PassiveTcpEstablishment optional
attribute indicates that the peer will listen prior
to establishing the connection.
Status: Optional, depending on local system
Optional
Attribute
Status: 1) The PassiveTcpEstablishment attribute SHOULD be
set to TRUE if this event occurs.
2) The DampPeerOscillations attribute SHOULD be set
to FALSE when this event occurs.
Event 5: AutomaticStart_with_PassiveTcpEstablishment
Definition: Local system automatically starts the BGP
connection with the PassiveTcpEstablishment
enabled. The PassiveTcpEstablishment optional
attribute indicates that the peer will listen prior
to establishing a connection.
Status: Optional, depending on local system
Optional
Attribute
Status: 1) The AllowAutomaticStart attribute SHOULD be set
to TRUE.
2) The PassiveTcpEstablishment attribute SHOULD be
set to TRUE.
3) If the DampPeerOscillations attribute is
supported, the DampPeerOscillations SHOULD be
set to FALSE.
Event 6: AutomaticStart_with_DampPeerOscillations
Definition: Local system automatically starts the BGP peer
connection with peer oscillation damping enabled.
The exact method of damping persistent peer
oscillations is determined by the implementation
and is outside the scope of this document.
Status: Optional, depending on local system.
Optional
Attribute
Status: 1) The AllowAutomaticStart attribute SHOULD be set
to TRUE.
2) The DampPeerOscillations attribute SHOULD be set
to TRUE.
3) The PassiveTcpEstablishment attribute SHOULD be
set to FALSE.
Event 7: AutomaticStart_with_DampPeerOscillations_and_
PassiveTcpEstablishment
Definition: Local system automatically starts the BGP peer
connection with peer oscillation damping enabled
and PassiveTcpEstablishment enabled. The exact
method of damping persistent peer oscillations is
determined by the implementation and is outside the
scope of this document.
Status: Optional, depending on local system
Optional
Attributes
Status: 1) The AllowAutomaticStart attribute SHOULD be set
to TRUE.
2) The DampPeerOscillations attribute SHOULD be set
to TRUE.
3) The PassiveTcpEstablishment attribute SHOULD be
set to TRUE.
Event 8: AutomaticStop
Definition: Local system automatically stops the BGP
connection.
An example of an automatic stop event is exceeding
the number of prefixes for a given peer and the
local system automatically disconnecting the peer.
Status: Optional, depending on local system
Optional
Attribute
Status: 1) The AllowAutomaticStop attribute SHOULD be TRUE.
8.1.3. Timer Events
Event 9: ConnectRetryTimer_Expires
Definition: An event generated when the ConnectRetryTimer
expires.
Status: Mandatory
Event 10: HoldTimer_Expires
Definition: An event generated when the HoldTimer expires.
Status: Mandatory
Event 11: KeepaliveTimer_Expires
Definition: An event generated when the KeepaliveTimer expires.
Status: Mandatory
Event 12: DelayOpenTimer_Expires
Definition: An event generated when the DelayOpenTimer expires.
Status: Optional
Optional
Attribute
Status: If this event occurs,
1) DelayOpen attribute SHOULD be set to TRUE,
2) DelayOpenTime attribute SHOULD be supported,
3) DelayOpenTimer SHOULD be supported.
Event 13: IdleHoldTimer_Expires
Definition: An event generated when the IdleHoldTimer expires,
indicating that the BGP connection has completed
waiting for the back-off period to prevent BGP peer
oscillation.
The IdleHoldTimer is only used when the persistent
peer oscillation damping function is enabled by
setting the DampPeerOscillations optional attribute
to TRUE.
Implementations not implementing the persistent
peer oscillation damping function may not have the
IdleHoldTimer.
Status: Optional
Optional
Attribute
Status: If this event occurs:
1) DampPeerOscillations attribute SHOULD be set to
TRUE.
2) IdleHoldTimer SHOULD have just expired.
8.1.4. TCP Connection-Based Events
Event 14: TcpConnection_Valid
Definition: Event indicating the local system reception of a
TCP connection request with a valid source IP
address, TCP port, destination IP address, and TCP
Port. The definition of invalid source and invalid
destination IP address is determined by the
implementation.
BGP’s destination port SHOULD be port 179, as
defined by IANA.
TCP connection request is denoted by the local
system receiving a TCP SYN.
Status: Optional
Optional
Attribute
Status: 1) The TrackTcpState attribute SHOULD be set to
TRUE if this event occurs.
Event 15: Tcp_CR_Invalid
Definition: Event indicating the local system reception of a
TCP connection request with either an invalid
source address or port number, or an invalid
destination address or port number.
BGP destination port number SHOULD be 179, as
defined by IANA.
A TCP connection request occurs when the local
system receives a TCP SYN.
Status: Optional
Optional
Attribute
Status: 1) The TrackTcpState attribute should be set to
TRUE if this event occurs.
Event 16: Tcp_CR_Acked
Definition: Event indicating the local system’s request to
establish a TCP connection to the remote peer.
The local system’s TCP connection sent a TCP SYN,
received a TCP SYN/ACK message, and sent a TCP ACK.
Status: Mandatory
Event 17: TcpConnectionConfirmed
Definition: Event indicating that the local system has received
a confirmation that the TCP connection has been
established by the remote site.
The remote peer’s TCP engine sent a TCP SYN. The
local peer’s TCP engine sent a SYN, ACK message and
now has received a final ACK.
Status: Mandatory
Event 18: TcpConnectionFails
Definition: Event indicating that the local system has received
a TCP connection failure notice.
The remote BGP peer’s TCP machine could have sent a
FIN. The local peer would respond with a FIN-ACK.
Another possibility is that the local peer
indicated a timeout in the TCP connection and
downed the connection.
Status: Mandatory
8.1.5. BGP Message-Based Events
Event 19: BGPOpen
Definition: An event is generated when a valid OPEN message has
been received.
Status: Mandatory
Optional
Attribute
Status: 1) The DelayOpen optional attribute SHOULD be set
to FALSE.
2) The DelayOpenTimer SHOULD not be running.
Event 20: BGPOpen with DelayOpenTimer running
Definition: An event is generated when a valid OPEN message has
been received for a peer that has a successfully
established transport connection and is currently
delaying the sending of a BGP open message.
Status: Optional
Optional
Attribute
Status: 1) The DelayOpen attribute SHOULD be set to TRUE.
2) The DelayOpenTimer SHOULD be running.
Event 21: BGPHeaderErr
Definition: An event is generated when a received BGP message
header is not valid.
Status: Mandatory
Event 22: BGPOpenMsgErr
Definition: An event is generated when an OPEN message has been
received with errors.
Status: Mandatory
Event 23: OpenCollisionDump
Definition: An event generated administratively when a
connection collision has been detected while
processing an incoming OPEN message and this
connection has been selected to be disconnected.
See Section 6.8 for more information on collision
detection.
Event 23 is an administrative action generated by
implementation logic that determines whether this
connection needs to be dropped per the rules in
Section 6.8. This event may occur if the FSM is
implemented as two linked state machines.
Status: Optional
Optional
Attribute
Status: If the state machine is to process this event in
the Established state,
1) CollisionDetectEstablishedState optional
attribute SHOULD be set to TRUE.
Please note: The OpenCollisionDump event can occur
in Idle, Connect, Active, OpenSent, and OpenConfirm
without any optional attributes being set.
Event 24: NotifMsgVerErr
Definition: An event is generated when a NOTIFICATION message
with "version error" is received.
Status: Mandatory
Event 25: NotifMsg
Definition: An event is generated when a NOTIFICATION message
is received and the error code is anything but
"version error".
Status: Mandatory