Static PCEP Link StateFutureweiBoston, MAUSAHuaimo.chen@futurewei.comVerizonUSAmehmet.toy@verizon.comVolta NetworksMcLeanVAUSAxufeng.liu.ietf@gmail.comFujitsuUSAliulei.kddi@gmail.comChina MobileNo.32 Xuanwumenxi Ave., Xicheng DistrictBeijing100032P.R. Chinali_zhenqiang@hotmail.com
Routing
PCE Working Group
This document presents extensions to
the Path Computation Element Communication Protocol (PCEP)
for a PCC to advertise the information about the links
without running IGP
and for a PCE to build a TED based on the information received.
A PCE architecture is described in RFC 4655,
in which a Traffic Engineering Database (TED) for a PCE
is constructed based on the link information
from IGP (OSPF or IS-IS) running in the domain
for which the PCE is responsible.
For a domain without running IGP,
the PCE responsible for the domain may obtain the link information
from a PCC running on each node in the domain.
This document presents extensions to
the Path Computation Element Communication Protocol (PCEP)
for a PCC to advertise the information about the links
attached to the node running the PCC
and for a PCE to build the TED
based on the information received from the PCC.
Area Border Router. Router used to connect two IGP areas (Areas in OSPF or levels in IS-IS).Autonomous System (AS) Border Router.
Router used to connect together ASes via inter-AS links.This document uses terminology defined in .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 .Since no IGP runs over any link,
we may not obtain any link information via IGP.
But links are configured.
For a point-to-point (P2P) link between nodes A and B,
from A's point of view, we have the following link information:
A link ID for the link is obtained if a user configures it;
otherwise, no link ID (i.e., the Router ID of A's neighbor) may
be obtained since no IGP adjacency over the link is formed.
For a broadcast link connecting multiple nodes,
on each of the nodes X, we have the same link information as above
except for:
In other words,
the information about the broadcast link obtained by node X
comprises a), b), 4) to 9),
but does not include any remote IP address or link ID.
A link ID for the link is obtained if a user configures it;
otherwise, no link ID (i.e., the interface address of the designated
router for the link) may be obtained since no IGP selects it.
A PCE constructs a TED for its responsible domain
after receiving the link information
from the PCC running on every node in the domain.
An existing Notification message may be extended
to advertise the information about links.
Alternatively, a new message can be used (refer to Appendix A).
The following new Notification-type (NT) and Notification-value (NV)
of a NOTIFICATION object in a Notification message are defined:
NT=8 (TBD): Links
NV=1: Update Links.
NT=8 and NV=1 indicates that the
PCC requests the PCE to update the link information based on
the TLVs in the object, which are described below. NV=2: Withdraw Links.
NT=8 and NV=2 indicates that the PCC asks the PCE to remove the Links
indicated by the TLVs in the object.A link TLV and a Router-ID TLV are defined.
The format of the link TLV is illustrated below.
The Type=tTBD1 indicates a link TLV Type.
The Length indicates the size of the Link Sub-TLVs.
A link TLV describes a single link.
It comprises a number of link sub-TLVs
for the information described in section 4,
which are the sub-TLVs defined in RFC 3630 or their equivalents
except for the local IP address with mask length defined below.
The format of the Router-ID TLV is shown below.
The Type=tTBD2 indicates a Router-ID TLV Type.
The Length indicates the size of the ID and flags field.
Undefined flags MUST be set to zero.
The ID indicates the ID of a router.
For a router not running IGP,
the ID may be the 32-bit or 48-bit ID of the router configured.
The format of the Sub-TLV for a local IPv4 address with
mask length is shown below.
The Type=stTBD1 indicates a local IPv4 Address with mask length.
The Length indicates the size of the IPv4 address and Mask Length.
The IPv4 Address indicates the local IPv4 address of a link.
The Mask Length indicates the length of the IPv4 address mask.
The format of the Sub-TLV for a local IPv6 address with
mask length is illustrated below.
The Type=stTBD2 indicates a local IPv6 Address with mask length.
The Length indicates the size of the IPv6 address and Mask Length.
The IPv6 Address indicates the local IPv6 address of a link.
The Mask Length indicates the length of the IPv6 address mask.
1. New or Changed LinksAfter the session between a PCC and a PCE is established,
the PCC sends the PCE
a message containing the information about the links attached
to the node running the PCC.
For any new or changed links,
the PCC sends the PCE a message containing the information
about these links
with indication of Update Links.
For example, for a new P2P link from node A,
the PCC running on A sends the PCE a Notification message having
a NOTIFICATION object with
NT=8 and NV=1 (indicating Update Links),
which contains a Router-ID TLV, followed by a link TLV.
The former comprises A's ID and flag I set to 1.
The latter comprises the Sub-TLVs for the information
described in section 4.
For multiple new or changed links from node A,
the PCC running on A sends the PCE a Notification message having
a NOTIFICATION object with NT=8 and NV=1,
which contains a Router-ID TLV for A's ID,
followed by multiple link TLVs for the links.
2. Links DownFor links down,
the PCC sends the PCE a message containing the information
about these links with indication of Withdraw Links.
For example, for multiple links from node A down,
the PCC running on A sends the PCE a Notification message having
a NOTIFICATION object with NT=8 and NV=2 (indicating Withdraw Links),
which contains a Router-ID TLV for A's ID,
followed by multiple link TLVs for the links.
The TLV for a P2P link comprises the Sub-TLVs
for the information on 1), 2) and 3) described in section 4.
The TLV for a broadcast link comprises the Sub-TLVs
for the information on a) and b) described in section 4.
3. Simplified Message
Alternatively, the messages may be simplified.
For each node,
the source IP address of the PCC running on the node may be
used as the ID of the node.
The PCE knows the address
after the session between the PCE and the PCC is up.
Thus, a message containing the information about links does not
need include any router-ID TLV.
For example, for a new P2P link attached to node A,
the PCC running on A sends the PCE
a Notification message having a NOTIFICATION object with
NT=8 and NV=1 (indicating Update Links), which
contains a link TLV comprising the Sub-TLVs for the information
on 1) to 9) described in section 4.
The object does not contain any Router-ID TLV for node A.
A PCE stores into its TED the links for each node
according to the messages for the links received
from the PCC running on the node.
For a message containing Update Links,
it updates the links accordingly.
For a message containing Withdraw Links, it removes the links.
When a node is down, the PCE removes the links attached to the node.
For a new P2P link between node A and B with no link ID configured,
when receiving a message containing the link from the PCC running on A,
the PCE stores the link for A (i.e., the link from A) into its TED.
It will find the link's remote end B using the remote IP address of the link.
After finding B, it associates the link for A with B and
the link for B with A.
This creates a bidirectional connection between A and B.
For a new broadcast link connecting multiple nodes
with no link ID configured,
when receiving a message containing the link from the PCC
running on each of the nodes X,
the PCE stores the link for X (i.e., the link from X) into its TED.
It will find the link's remote end P
using the link's local IP address with network mask.
P is a Pseudo node identified by the local IP address of
the designated node selected from the nodes connected to the link.
After finding P, it associates the link for X with P and
the link for P with X.
This creates a bidirectional connection between X and P.
The first node and second node from which the PCE receives
a message containing the link is selected as
the designed node and backup designed node respectively.
After the designed node is down,
the backup designed node becomes the designed node and
the node other than the designed node
with the largest local IP address connecting to the link
is selected as the backup designed node.
When the old designed node is down and
the backup designed node becomes the new designed node,
the PCE updates its TED through
removing the link between each of nodes X and old P
(the Pseudo node corresponding to the old designed node) and
adding a link between each of nodes X
(still connecting to the broadcast link) and new P
(the Pseudo node corresponding to the new designed node).
The mechanism described in this document does not raise any new security issues for the PCEP protocols.This section specifies requests for IANA allocation.The authors would like to thank Jescia Chen, and Eric Wu
for their valuable comments on this draft.A new message may be defined to advertise
the information on links.
The format of the message for the information on Links (IL for short) is as follows:
::=
where:
::= []
]]>
Where the value of the Message-Type in the Common Header
indicates the new message type.
The exact value is to be assigned by IANA.
A new RP (NRP) object will be defined,
which follows the Common Header.
A new flag W (Withdraw) in the NRP object is defined
to indicate whether the links are withdrawn.
When flag W is set to one, the PCE removes the links
in the message after receiving it from the PCC.
When flag W is set to zero, the PCE adds/updates
the links in the message.
An alternative to flag W in the NRP object is a similar flag W
in each LINK object.
For example, when the flag is set to one in the LINK object,
the PCE removes the links in the object.
When the flag is set to zero,
the PCE adds/updates the links in the object.
The format of a LINK object body is as follows:
Flag W=1 indicates Withdraw links. W=0 indicates Updated links.
Router-ID TLV is optional. Link TLVs are mandatory.
They are the same as described in section 5.