PCE for Mirror BindingFutureweiBoston, MAUSAhchen.ietf@gmail.com Orange Francebruno.decraene@orange.comVerizon13101 Columbia PikeSilver SpringMD 20904USA 301 502-1347gyan.s.mishra@verizon.comChina TelecomBeiqijia Town, Changping DistrictBeijing102209Chinawangaj3@chinatelecom.cnIBM CorporationUSAxufeng.liu.ietf@gmail.comFujitsuUSAliulei.kddi@gmail.comPCE is used to distribute a binding
to a node. The binding includes a binding SID and
a path represented by a list of SIDs.
This document describes extensions to PCEP for distributing
the information about the binding to a protecting node.
For an SR path via the node with the binding SID,
when the node fails,
the protecting node such
as the upstream neighbor on the path uses the information to protect
the binding SID of the failed node.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119.
specifies how PCE may be used to distribute a
Segment Routing (SR) Policy to a node in a network.
An SR Policy may contain a binding, which includes
a binding SID and a path associated with the binding SID.
The path is represented by a list of SIDs.
After a PCE as a controller distributes
the binding to the node, the
node forwards the packet with the binding SID according to the first
SID in the list. It replaces the binding SID in the packet with the
list of SIDs and forwards the packet using the FIB entry for the top
SID (i.e., the first SID) in the packet.
When the node fails, suppose that the upstream neighbor (as PLR) of
the node has the corresponding binding protection information for
protecting the binding SID of the node. The information includes the
binding SID, the list of SIDs and an identifier of the node. After
the upstream neighbor as PLR detects the failure of the node, for a
packet with the node SID of the failed node received, it protects the
binding SID of the failed node. It pops the node SID, replaces the
binding SID in the packet with the list of SIDs, forwards the packet
without going through the failed node towards the top SID (i.e., the
first SID, assuming it is a node SID for simplicity here). How a
upstream node protect the binding SID of the failed node is out of
scope of this document and described in
and
(Note: the second reference will be removed after
the first one includes enough text for
protecting binding SIDs of a node).
This document proposes some procedures and extensions
to PCEP for distributing the binding protection information
to the possible protecting nodes, which are the nodes that may protect
the failed node.
A PCC may run on each node
in a network.
A PCE runs on a server as a controller to communicate with PCCs.
The PCE and the PCCs
work together to distribute the binding protection information
about a binding SID
on a node to the possible protecting nodes
for protecting the binding SID of the node when the node fails.When a PCE and a PCC running on a network node
establish a PCEP session between them, they exchange
their capabilities of Binding
Protection Information Distribution in Open messages.
An Open message includes an Open object. The object contains
a PATH_SETUP_TYPE_CAPABILITY TLV with Path Setup Type (PST) = TBD1
and a new sub-TLV, called Binding Protection Information Distribution
Capability (BSID-D for short) sub-TLV.
PST = TBD1 indicates Binding Protection Information
Distribution.BSID-D sub-TLV contains parameters used for
Binding Protection Information distribution.The format of BSID-D sub-TLV is shown in
. TBD2 is to be assigned by IANA. 4. 2 octets. Must be set to zero in transmission
and ignored on reception. 2 octets. No flag bits are defined.A PCC, which supports the capability of
Binding Protection Information Distribution,
sends a PCE an Open message containing
a PATH_SETUP_TYPE_CAPABILITY TLV with Path Setup Type (PST) = TBD1
and a BSID_PROTECTION_DISTRIBUTION_CAPABILITY sub-TLV.
PST = TBD1 indicates that the PCC is capable of receiving and processing
the binding protection information about a binding SID
on a node from the PCE
for protecting the binding SID of the node when the node fails.A PCE, which supports the capability of
Binding Protection Information Distribution,
sends a PCC an Open message containing
a PATH_SETUP_TYPE_CAPABILITY TLV with Path Setup Type (PST) = TBD1
and a BSID_PROTECTION_DISTRIBUTION_CAPABILITY sub-TLV.
PST = TBD1 indicates that the PCE supports the capability of
Binding Protection Information Distribution.If both a PCC and a PCE support the capability of
Binding Protection Information Distribution,
each of the Open messages sent by the PCC and PCE contains
a PATH-SETUP-TYPE-CAPABILITY TLV with a PST list containing PST = TBD1 and
a BSID_PROTECTION_DISTRIBUTION_CAPABILITY sub-TLV.If a PCE receives an Open message without a
PATH-SETUP-TYPE-CAPABILITY TLV containing PST = TBD1 from a PCC,
then the PCE MUST not send the PCC
any binding protection information.If a PCC receives an Open message without a
PATH-SETUP-TYPE-CAPABILITY TLV containing PST = TBD1 from a PCE,
then the PCC MUST ignore any binding protection information
from the PCE.When PCECC is used,
a PCC and PCE exchange capability of
binding protection information distribution
using PCECC-CAPABILITY Sub-TLV
which is included in the PATH_SETUP_TYPE_CAPABILITY TLV in an Open message.
A new flag bit B is defined in the Flags field of the
PCECC-CAPABILITY sub-TLV as shown in
.
B flag (for Binding SID Protection):
if set to 1 by a PCEP speaker (PCE or PCC),
the B flag indicates that the PCEP
speaker supports and is willing to handle the PCECC based
central controller instructions for Binding SID protection.
The bit MUST be set to 1 by both a PCC and a PCE for the PCECC
Binding SID protection instruction download/report on a PCEP session.
After sending the binding to a node
(i.e., the PCC running on the node),
a PCE sends the corresponding binding protection
information to the possible protecting nodes of the node
in a PCEP message
such as a Path Computation LSP Update Request (PCUpd) message.
The message contains a Request Parameters (RP) object or
Stateful PCE Request Parameters (SRP) object.
The object includes:
A PATH-SETUP-TYPE TLV with PST = TBD1 indicating
binding protection information for a Binding SID
of a node.A Node ID TLV containing the identifier of the node.The format of PATH-SETUP-TYPE TLV is shown in
.
The format of Node ID TLV
is illustrated in . Its value (TBDa) is to be assigned by IANA.Its value indicates the length
of the value field of the TLV is 4. 4-octet field
contains the 4-octet TE router identifier (ID) of
the (protected) node.When a PCE sends a binding to node N
(i.e., PCC running on N)
in a first Path Computation LSP Update Request (PCUpd) message,
the PCE sends the corresponding binding
protection information to the possible protecting nodes
such as neighbors of node N in a second PCUpd message.
The first message contains an RP/SRP object and
an LSP object with a TE-PATH-BINDING TLV.
The RP/SRP object does not include any PATH-SETUP-TYPE TLV with PST = TBD1.
The TLV includes a binding SID and R bit set to zero.
The second message contains an RP/SRP object and
an LSP object with a TE-PATH-BINDING TLV.
The RP/SRP object includes a PATH-SETUP-TYPE TLV with PST = TBD1 and
a Node ID TLV indicating node N.
TE-PATH-BINDING TLV includes the binding SID and R bit set to zero.
After a PCE sends the binding to node N,
if the PCE removes the binding from node N through sending
a third PCUpd message to node N, the PCE removes the corresponding
binding protection information from the nodes through
sending a fourth PCUpd message to the nodes.
The third message contains an RP/SRP object and
an LSP object with a TE-PATH-BINDING TLV.
The RP/SRP object does not include any PATH-SETUP-TYPE TLV with PST = TBD1.
The TLV includes a binding SID and R bit set to one (1).
The fourth message contains an RP/SRP object and
an LSP object with a TE-PATH-BINDING TLV.
The RP/SRP object includes a PATH-SETUP-TYPE TLV with PST = TBD1 and
a Node ID TLV indicating node N.
TE-PATH-BINDING TLV includes the binding SID and R bit set to one (1).
After a PCE sends the binding to node N,
if the PCE changes the binding in node N through
sending a fifth PCUpd message to node N, the PCE changes the
corresponding binding protection information in the nodes
through sending a sixth PCUpd message to the them.
The fifth message contains an RP/SRP object and
an LSP object with a TE-PATH-BINDING TLV.
The RP/SRP object does not include any PATH-SETUP-TYPE TLV with PST = TBD1.
The LSP object includes a (changed) path.
The TLV includes a binding SID and R bit set to zero.
The sixth message contains an RP/SRP object and
an LSP object with a TE-PATH-BINDING TLV.
The RP/SRP object includes a PATH-SETUP-TYPE TLV with PST = TBD1 and
a Node ID TLV indicating node N.
The LSP object includes the (changed) path.
TE-PATH-BINDING TLV includes the binding SID and R bit set to zero.
AcknowledgmentsThe authors would like to thank
Andrew Stone, and Dhruv Dhody
for their comments to this work.