Internet DRAFT - draft-wijnands-rtgwg-mcast-frr-tn
draft-wijnands-rtgwg-mcast-frr-tn
Routing Working Group IJ. Wijnands, Ed.
Internet-Draft L. De Ghein
Intended status: Standards Track Cisco
Expires: July 28, 2014 G. Enyedi, Ed.
A. Csaszar
J. Tantsura
Ericsson
January 24, 2014
Tree Notification to Improve Multicast Fast Reroute
draft-wijnands-rtgwg-mcast-frr-tn-02
Abstract
This draft proposes dataplane triggered Tree Notifications to support
multicast fast reroute for PIM and mLDP. These Tree Notifications
are initiated by a node detecting the failure to a Repair Node
downstream. A Repair Node is a node that has a pre-built backup path
that can circumvent the failure. Using this mechanism, a Repair Node
has the ability to learn about non-local failures quickly without
having to wait for the IGP to convergence. This draft also covers an
optional method to avoid bandwidth usage on the pre-built backup
path.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on July 28, 2014.
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents
1. Terminology and Definitions . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Improving Non-local failures . . . . . . . . . . . . . . . . . 4
3.1. Downstream Tree Notifications . . . . . . . . . . . . . . 5
3.2. DTN processing logic . . . . . . . . . . . . . . . . . . . 5
3.3. Repair Node discovery . . . . . . . . . . . . . . . . . . 7
3.3.1. Repair Node Information item . . . . . . . . . . . . . 8
4. Reduce the bandwidth consumption in networks with fast
failover response times . . . . . . . . . . . . . . . . . . . 8
4.1. Joining a secondary tree in blocking mode . . . . . . . . 9
4.2. Upstream Tree Notifications . . . . . . . . . . . . . . . 9
5. MRT/MCI-Only Mode . . . . . . . . . . . . . . . . . . . . . . 10
6. TN Authentication . . . . . . . . . . . . . . . . . . . . . . 10
7. The TN Packet . . . . . . . . . . . . . . . . . . . . . . . . 11
7.1. TN Packet Format . . . . . . . . . . . . . . . . . . . . . 11
7.1.1. TN TimeStamp TLV Format . . . . . . . . . . . . . . . 13
7.1.2. TN Signature TLV Format . . . . . . . . . . . . . . . 13
8. PIM Specific TN Components . . . . . . . . . . . . . . . . . . 14
8.1. RNI item in PIM Join Message . . . . . . . . . . . . . . . 14
8.2. Tree Information Item . . . . . . . . . . . . . . . . . . 16
8.3. Incremental deployment . . . . . . . . . . . . . . . . . . 17
9. mLDP Specific TN Components . . . . . . . . . . . . . . . . . 17
9.1. RNI item in mLDP Label Mapping . . . . . . . . . . . . . . 18
9.2. Tree Information Item . . . . . . . . . . . . . . . . . . 19
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 19
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
12. Security Considerations . . . . . . . . . . . . . . . . . . . 20
13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20
13.1. Normative References . . . . . . . . . . . . . . . . . . . 20
13.2. Informative References . . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21
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1. Terminology and Definitions
MoFRR : Multicast only Fast Re-Route.
LFA : Loop Free Alternate.
mLDP : Multi-point Label Distribution Protocol.
PIM : Protocol Independent Multicast.
UMH : Upstream Multicast Hop, a candidate next-hop that can be used
to reach the root of the tree.
tree : Either a PIM (S,G)/(*,G) tree or a mLDP P2MP or MP2MP LSP.
OIF : Outgoing InterFace, an interface used to forward multicast
packets down the tree towards the receivers. Either a PIM
(S,G)/(*,G) tree or a mLDP P2MP or MP2MP LSP.
IIF : Incoming InterFace, an interface where multicast traffic is
received by a router.
MCE : MultiCast Egress, the last node where the multicast stream
exits the current transport technology (MPLS-mLDP or IP-PIM)
domain or administrative domain. This maybe the router attached
to a multicast receiver.
MCI : MultiCast Ingress, the node where the multicast stream enters
the current transport technology (MPLS-mLDP or IP-PIM) domain.
This maybe the router attached to the multicast source.
DTN : Downstream Tree Notification.
UTN : Upstream Tree Notification.
TN : Tree Notification, Upstream or Downstream
JM : Join Message, the message used to join to a multicast tree,
i.e. to build up the tree. In PIM, this is a JOIN message, while
in mLDP this corresponds to a Label Mapping message.
MRT : Maximally Redundant Trees.
Repair Node : The node performing a dual-join to the tree through
two different UMHs. Sometimes also called as dual-joining node or
merging node (it merges the secondary and primary tree).
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RNI : The Repair Node Information is an item included in the TN
which holds the nessesary repair information when the TN is send
to the Repair Node.
Branching Node : A node, (i) which is considered as being on the
primary tree by its immediate UMH and (ii) which has at least one
OIF on the secondary tree installed for a multicast tree.
2. Introduction
Both [I-D.karan-mofrr] and [I-D.atlas-rtgwg-mrt-mc-arch] describe
"live-live" multicast protection, where a node joins a tree via
different candidate upstream multicast hops (UMH). With MoFRR the
list of candidate UMHs can come from either ECMP or Loop Free
Alternate (LFA) paths towards the MultiCast Ingress node (MCI). With
MRT, the candidate UMHs are determined by looking up the MCI in two
different (Red and Blue) topologies. In either case, the multicast
traffic is simultaneously received over different paths/topologies
for the same tree. The node 'dual-joining' the tree needs a
mechanism to prevent duplicate packets being forwarded to the end
user. For that reason a node 'dual-joining' the tree only accepts
packets from one of the UMHs at the time. Which UMH is preferred is
a local decision that can be based on IGP reachability, link status,
BFD, traffic flow monitoring, etc...
Should the node detect a local failure on the primary UMH, the node
has an instantly available secondary UMH that it can switch to,
simply by unblocking the secondary UMH. The dual-joining node is
also called Repair Node in the following.
This draft attempts to improve these solutions by:
o Improving fail-over time and the reliability of failure detection
for non-local failures; and
o Reducing the bandwidth consumption in a network with fast failover
response times, by avoiding sending the multicast traffic over the
secondary path.
3. Improving Non-local failures
If a failure is not local and happens further upstream, the dual-
joining node needs a fast mechanism (i) to detect the upstream
failure and (ii) to learn that other upstream nodes cannot circumvent
the failure. Existing methods based on traffic monitoring are
limited in scope and work best with a steady state packet flow.
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Therefore, we propose a method which can trigger the unblocking the
secondary UMH independently of the packet flow.
Figure 1 shows an example. Consider that, e.g., node A goes down.
Nodes C, D and E cannot detect that locally, so they need to resort
to other means. After detecting the failure, node C should not
change to its secondary UMH (node J) as it won't help for the failure
of A. Node D, on the other hand, will have to unblock its secondary
UMH (node I). Yet again, with MoFRR, node E should not unblock its
secondary UMH (node K): (i) this won't help in resolving the failure
of node A, and (ii) one of its upstream nodes (node D in this case)
will be able to restore the stream with a fail-over action.
3.1. Downstream Tree Notifications
When a node detects a local failure of its primary UMH it MUST
originate a Downstream Tree Notification (DTN) to all the Repair
Nodes directly below it in the multicast tree. The method of
discovering such nodes is described in Section 3.3. When a Repair
Node receives a DTN containing the primary UMH of the node, it must
switch to the secondary UMH.
DTN packets are sent to the Repair Node via unicast. The packet may
be forwarded using any transport that is available (MPLS or IP) to
reach the destination. The IP precedence in the IP header should
have a value of 6 (Internetwork Control). The EXP field (Traffic
Class field) in the MPLS header should have a value of 6. The DTN
packets are identified by a well known port number (to be allocated).
Using a well-known port number it is easy for the Repair Node to
identify the DTN packet and invoke the procedures as described in
this draft. We are proposing to allocate different port numbers for
PIM and mDLP since it will be easier to dispatch the packet to the
right process dealing with this request.
When a router detects a local failure, it should sent out the DTN
packet to the Repair Node as fast as possible. The sooner the Repair
Node gets the packet, the sooner the traffic can be restored. It is
recommended that the DTN packet is pre-created and originated from
the data-plane. The same is true for receiving the DTN packet on the
Repair Node, the faster it can be processed, the faster the traffic
is restored. For both forwarding and processing the DTN, control-
plane interaction SHOULD be avoided to get the best failover results.
3.2. DTN processing logic
When a DTN packet is received on the Repair Node it must determine
which tree and UMH the notification is for. The information encoded
in the DTN is specific for the type of tree being used, i.e. PIM vs
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mLDP. For details on the specific encoding see Section 8 and
Section 9 for the details. Once the Repair node has determined the
tree and the UMH, the following rules are use for processing the DTN.
1. If the UMH encoded in the DTN packet is the primary UMH in the
tree, the secondary UMH MUST become the new primary UMH and the
old primary MUST become the secondary.
2. If the UMH encoded in the DTN packet is the secondary UMH in the
tree, no action needs to be taken.
3. If a DTN notification has been received for both the primary and
secondary UMH in the tree, a new DTN notification MUST be
originated to the Repair Node(s) downstream from this node.
In order for the Repair Node to determine that a DTN notification was
received for both the primary and secondary UMH, it must store the
fact a DTN was received for a particular UMH.
Consider the example in Figure 1 below. MCI is the root of a tree
that includes the nodes as follows (based on the primary UMH).
->F->G->H->I
MCI
->A->B->C->D->E
Node C, D and E are candidate Repair Nodes.
-- Primary UMH
++ Secondary UMH
+-+ +-+ +-+ +-+
|F|+++|G|+++|H|+++|I|
+-+ +-+ +-+ +-+
+ +
+ +
+---+ +-+ +-+ +-+ +-+ +-+
Source ---|MCI|------|A|---|B|---|C|---|D|---|E|--- Receiver
+---+ +-+ +-+ +-+ +-+ +-+
+ + + +
+ + + +
+-+ +-+
|J| |K|
+-+ +-+
Figure 1: Remote failure example
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Suppose that the link between node A and B failed, B is directly
connected and will detect the failure locally. In this case, node B
is the only node that detects the failure and will originate a DTN to
its downstream repair node C. Node C will receive the DTN for the UMH
that is the primary UMH. Following rule 1 (Section 3.2), node C will
make the backup UHM the new primary. No further action is needed
because C has repaired the tree via node J. Note, J would not have
sent a DTN to node C because J is not directly connected to the
failing link.
Suppose that node A fails, B and J are directly connected and detect
the failure locally. A DTN packet is triggered to first downstream
repair node of A, which is node C. Node C is an unusable Repair Node
because it will receive DTN for both the primary UMH (from B) and the
secondary UMH (from J). Following rule 3 (Section 3.2), C can't
repair the tree and must sent a new DTN packet towards the Repair
Nodes of C, which are D, on the primary path, and E, on the secondary
path.
Suppose that the link between A and the MCI failed. Node A is
directly connected to the failure and will trigger a DTN packet to
its downstream repair node(s). In this case, node A has learned
about the downstream repair node C twice, the primary UMH (via node
B) and secondary UMH (via node J). Node A will therefore sent a DTN
packet including both the primary and secondary UMH to node C (see
Section 7 for details on the encoding). Following rule 3
(Section 3.2), C can't repair the tree and must sent a new DTN packet
towards the Repair Nodes of C, which are D, on the primary path, and
E, on the secondary path.
The DTN packet that D received from C will match against the primary
UMH. Following rule 1, D will activate the backup path to I. The DTN
packet that E received from C will match against the backup UMH,
following rule 2, no action is taken. In the example one can see
that we recovered from the failure because node D started accepting
the data packets from node I and is forwarding them to node E.
3.3. Repair Node discovery
In example Figure 1 we wrote that nodes C, D and E are the repair
nodes. How does a node determine that it is a Repair Node? The rule
is straightforward, a node that is enabled to join two UMH's, one in
active the other in backup ([I-D.karan-mofrr]), is a repair node on
the tree. A Repair node has the ability to repair the tree for the
nodes upstream from this node. In order for the Repair Node to get
notified of upstream failures (ie DTN), the nodes upstream from the
Repair Node need to learn about it.
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3.3.1. Repair Node Information item
A Repair Node MUST advertise its own address (either a router ID or
any directly connected address) and an UMH identifier to the nodes
upstream on the tree. This address and UMH are part of the RNI
(Repair Node Information) item that is included in the JM. The RNI
is carried hop by hop in the JM upstream. If a node along the path
is not a Repair Node, it will save the RNI and forward if further
upstream. If the node is Repair Node, it will save the RNI and
include its own RNI in the JM sent further upstream. If a Repair
Node changes one if its UMH's, it needs to trigger a new RNI to its
upstream node(s) to notify them of the changed UMH. If a RNI is
received and it does not match the saved RNI, the new RNI overrides
the old RNI and triggers a JM with the new RNI to its upstream
node(s). A RNI includes protocol specific information on how to
identify the tree and UMH. For that reason it is documented in the
protocol specific sections Section 8 and Section 9.
The Repair Node MAY include additional information in the RNI for
reasons of security and robustness, please see Section 6 and
Section 7.1.
4. Reduce the bandwidth consumption in networks with fast failover
response times
In some of networks, such as aggregation networks, bandwidth is more
sparse than, e.g., in core networks. Live-live multicast protection
results in more bandwidth consumption in the network as it
continuously pulls traffic on both trees. In such networks it is
relevant if the capacity serving backup purposes can be used, most of
the time, by best-effort or even by lower-than-best-effort traffic.
+---+ +-+ +-+
|MCI|~~~~~~|A|---|B|
+---+ +-+ +-+
\\ //
\\ //
+-+
|C|
+-+
Nodes A and B have receivers. Double lines show bandwidth
consumption that is superfluous when there is no failure in the
network.
Figure 2: Example for secondary segments occupying bandwidth in MoFRR
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In live-standby mode the aim is that the secondary tree is not
forwarding multicast traffic as long as there is no failure. In
order to achive such a "live-standby" multicast protection the
following procedures must be followed:
o Upsteam nodes block their OIF when they are part of a standby
tree.
o If all of the OIF's of the node are marked as blocking, the node
joins the tree in blocking mode further upstream.
o A procedure so that the upstream node can quickly unblock its OIF
and starts to forward.
4.1. Joining a secondary tree in blocking mode
The JM sent to the secondary UMH includes an identifier to indicate
the upstream node MUST not forward packets down this branch of the
tree. The identifier is TBD. The mechanism to join a secondary path
is identical to what the MRT and MoFRR drafts describe, i.e. a Repair
Node simply sends a secondary JM through another UMH (on another
topology, in case of MRT). If a node receives a JM without a
blocking identifier for an OIF that previously was in blocking mode,
the blocking mode is reset and the node stats forwarding out of this
interface. If this node joined the tree in blocking mode further
upstream, a new JM MUST be originated to reset the blocking state
further upstream.
4.2. Upstream Tree Notifications
In order to make an upstream node start forwarding on the backup path
quickly after a failure was detected on the primary UMH, we sent a
Upstream Tree Notification (UTN) to the upstream node on the backup
UMH. The failure on the primary UMH may be local or detected using a
DTN. The UTN received by the upstream node should be processed in
the data-plane and reset the blocking state of the OIF. If this node
also joined the tree in blocking mode upstream, a UTN has to be
forwarded further upstream. This procedure is repeated until we find
a node that is not in blocking mode or we reached the MCI.
When the upstream node resets the blocking mode in the data-plane,
the control plane will still have the blocking mode set. In order
for the control plane to get in sync with the data-plane, the node
that originated the UTN MUST also trigger a JM without blocking mode.
The upstream node receiving the UTN must be able to identify the tree
which the notification is sent for, as well as the downstream
interface it applies to. The information is encoded in a same RNI
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item that is used for DTN packets. For details please see the
protocol specific sections Section 8 and Section 9.
Like DTN packets, UTN packets are sent via unicast to the upstream
node.
5. MRT/MCI-Only Mode
If each node in the network supports UTN and also all nodes support
MRT, the nodes may work in "MRT/MCI-only" mode.
In MRT/MCI-only mode, there is one single Repair Node for all
failures, the MCI. Other nodes MUST NOT consider themselves as
Repair Nodes. MRT ensures the necessary maximally disjoint secondary
tree up to the MCI, on a second topology. Only the MCI MUST keep its
OIFs corresponding to the secondary tree blocked. Similarly, only
MCEs MUST keep their secondary backup IIFs blocked. Any other nodes
MUST NOT block their (secondary) IIFs or OIFs.
In MRT/MCI-only mode, the UTNP MUST be forwarded directly to the MCI.
This mode enables that a node detecting a downstream failure of the
primary tree MAY send a UTNP upstream towards the source/MCI on the
primary tree.
If an UTNP is received by the MCI on the secondary topology in "MRT/
MCI-only" mode, the MCI MUST unblock the OIF where the UTNP was
received. This activates a whole sub-tree of the secondary tree.
If an UTNP is received by the MCI on the primary topology in "MRT/
MCI-only" mode, the MCI gets no information on which leg to activate
on the secondary tree, so it MUST activate (unblock) all secondary
legs.
6. TN Authentication
If a malicious attacker can reproduce the TN packet format, unwanted
reconvergence can be triggered. In order to avoid such attack, a TN
packet MAY contain a digital signature. Having authentication is
optional, it can be enabled or disabled in the network. If however
security is enabled, all the nodes must share the same secret key,
which they get either by configuration or from the multicast routing
protocol. Moreover, for protection against reply attacks, each TN
packet must contain a sequence number.
The sequence numbers in the network are not necessarily synchronised,
instead, each node can have its own. Sequence numbers can be
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generated arbitrarily, it can be even some random value; the only
requirement is to create a new sequence number each time a
reconvergence was triggered due to a TN (i.e. the sequence number was
used).
The originator of the DTN packet MUST use the sequence number of the
Repair Node to create a TN signature TLV (see Section 7.1.2). For
UTN packet the sender MUST use its own sequence number, what it sent
previously to its UMH. The destination in this case must check
validity based on the sequence number of the sender.
A sequence number is learned from JM and part of the RNI. It is the
responsibility of multicast routing protocol to protect JM against
malicious change.
7. The TN Packet
7.1. TN Packet Format
A Tree Notification is an IPv4 or IPv6 UDP packet with the following
format.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version Nr | Address Family | Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Originator ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TreeInfo Count | TreeInfo size |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TreeInfo item - 1 |
~ . ~
| TreeInfo item - n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TN option TLVs ... |
. .
. .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Version number: This is a 1 octet field encoding the version
number, currently 0.
Address Family: This is a 2 octet field encoding a value from
ADDRESS FAMILY NUMBERS in [RFC3232] that encodes the address
family for the Root Address of the tree.
Type: This is a 1 octet field encoding the message type, currently
two are defined;
Type 0: Downstream Tree Notification.
Type 1: Upstream Tree Notification.
Originator ID: 4 bytes long unique ID of the originator. That can
be some loopback IPv4 address if there is such, or can be set by
the operator.
Sequence Number: Number unique for each failure case. It is
recommend to start at 0, and to be increased by 1 each time a new
TN is originated. The Sequence number may differ at each node,
thus the sender and the receiver must know the same sequence
number.
TreeInfo count: 2 octet field encoding the number of TreeInfo items
includes.
TreeInfo size: 2 octet field encoding the number of octets use to
encode the TreeInfo's following.
TreeInfo item: The encoding of this field is protocol specific, see
Section 8 and Section 9.
TN option TLVs: TLVs (Type-Length-Value tuples) describing
additional options for TN packets.
The TLV's have the following format.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value |
. .
. .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: This is a 2 octet field encoding the type number of the TLV.
Length: This is a 2 octet field encoding the length of the Value in
octets.
Value: String of Length octets, to be interpreted as specified by
the Type field.
7.1.1. TN TimeStamp TLV Format
The TimeStamp is an optional TLV that MAY be included when the TN was
originated, it has the following format.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 0 | Length = 8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TimeStamp Sent (seconds) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TimeStamp Sent (microseconds) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
TimeStamp: The TimeStamp is the time-of-day (in seconds and
microseconds, according to the sender's clock) in NTP format [NTP]
when the Tree Notification is sent.
7.1.2. TN Signature TLV Format
TN Signature is an optional TLV, which protects the whole TNP
(including other TLVs) against attacks thus it must be the last TLV
if present. The signature is SHA-512 hash value. The input of the
hash function is as follows:
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Complete packet content without signature TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Secret key |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Signature input: The input of the hash function is the packet
extended with TN security key
The build up of the TLV is as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 1 | Length = 64 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Hash function result |
. .
. .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Signature: SHA-512 signature protecting TN packets.
8. PIM Specific TN Components
In this section we are documenting the PIM specific data-structures
and procedures (if they are different from the generic procedures are
defined in this document). As described in this document, TN packets
are UDP/IP packets sent via unicast to its destination. The UDP port
number for PIM is set to the (to be) assigned IANA port number for
PIM-TN.
8.1. RNI item in PIM Join Message
As described previously, PIM must insert the RNI when sending a PIM
join to its UMH. The RNI includes its router ID, sequence number and
UMH Identifier. The UMH-ID can be locally unique identifier since
its has only local significance on the Repair Node. A good ID to use
would be the IP address of the interface associated with the UMH the
PIM join is sent to. The RNI is carried in the PIM Join as a new PIM
Attribute following [RFC5384]. The PIM RNI attribute has the
following format for IPv4.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|F|E| Type | Length | Sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Repair Node address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| UMH-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
F Forward if not understood.
E End of Attributes, following [RFC5384].
Type: This 6 bit field should be assigned by IANA for TN specific
JOIN messages.
Length: Length = 10 octets.
Sequence number: 2 octets long field, describing the sequence
number of the sending Repair Node.
Repair Node address: The router ID of the Repair Node, in IPv4
address format.
UMH-ID: This is a 4 octet field encoding UMH identifier. This is
the IPv4 address of the interface associated with the UMH the PIM
join is sent to.
Figure 3: PIM IPv4 RNI attribute TLV
The PIM RNI attribute has the following format for IPv6.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|F|E| Type | Length | Sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Repair Node address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ UMH-ID ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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F Forward if not understood.
E End of Attributes, following [RFC5384].
Type: This 6 bit field should be assigned by IANA for TN specific
JOIN messages.
Length: Length = 16 octets.
Sequence number: 2 octets long field, describing the sequence
number of the sending Repair Node.
Repair Node address: The router ID of the Repair Node, in IPv4
address format.
UMH-ID: This is a 16 octet field encoding UMH identifier. This is
the IPv6 address of the interface associated with the UMH the PIM
join is sent to.
Figure 4: PIM IPv6 RNI attribute TLV
8.2. Tree Information Item
A TN packet contains one or more TreeInfo items that allows a Merge
Node to idenfy which tree(s) and interface(s) are effected by the TN.
The same encoding is used for DTN and UTN packets. The PIM TreeInfo
items are defined for IPv4 and IPv6. Which version is to be included
in the TN packet depends on Address Family in the TN packet. The
UMH-ID included in the DTN MUST be taken from the RNI that was
signalled for that tree. The UMH-ID for UTN packets is the PIM
neighbor address for that tree. The TreeInfo item has the following
format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Source address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 group address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| UMH-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Source Address: This is a 4 octet field encoding the IPv4 source
address of the tree. A source address of 0.0.0.0 means that this
TN relates to a (*,G) tree.
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Group Address: This is a 4 octet field encoding the IPv4 group
address of the tree.
UMH-ID: This is a 4 octet field encoding UMH identifier.
Figure 5: PIM IPv4 TreeInfo item
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ IPv6 Source address ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ IPv6 group address ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ UMH-ID ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Source Address: This is a 16 octet field encoding the IPv6 source
address of the tree. A source address of 0:0:0:0:0:0:0:0 means
that this TN relates to a (*,G) tree.
Group Address: This is a 16 octet field encoding the IPv6 group
address of the tree.
UMH-ID: This is a 16 octet field encoding UMH identifier.
Figure 6: PIM IPv6 TreeInfo item
8.3. Incremental deployment
Joins with a RNI can be forwarded through legacy nodes if the
Transitive Attribute (see [RFC5384]) has the F bit set to 1. It is
up to the network operator to determine this. The DTN functionality
can be deployed incrementally as long as the node detecting the
failure and Repair Nodes support it.
9. mLDP Specific TN Components
In this section we are documenting the mLDP specific data-structures
and procedures (if they are different from the generic procedures are
defined in this document). As described in this document, TN packets
are UDP/IP packets sent via unicast to its destination. The UDP port
number for mLDP is set to the (to be) assigned IANA port number for
mLDP-TN.
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9.1. RNI item in mLDP Label Mapping
The RNI item for mLDP is encoded in a LDP MP Status TLV as documented
in [RFC6388] section 5. A new LDP MP Status Value Element is created
for this purpose and called the RNI Status. The RNI Status includes
the router ID, sequence number and UMH Identifier. The UMH-ID can be
locally unique identifier since its has only local significance on
the Repair node. For mLDP the value that MUST be used is the Local
Label associated with the UMH the mLDP Label Mapping is sent to. The
RNI status is carried in Label Mapping messages and has the following
format.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RNI | Length | Seq. Number .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. | IPv4 Repair Node address .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. | UMH-ID reserved | UMH-ID Label .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. |
+-+-+-+-+-+-+-+-+
RNI Type: This 1 octet field assigned by IANA for RNI Status Value
Element Types.
Length: This is a 2 octet field, describing the length of the
Value, Length = 10 octets.
Sequence number: 2 octets long field, describing the sequence
number of the sending Repair Node.
IPv4 Repair Node address: The IPv4 address of the Repair Node.
UMH-ID reserved: 12 bit field, reserved.
UMH-ID Label: This is a 20 bit field encoding a Label as UMH
identifier.
Figure 7: mLDP RNI Status Value Element
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| RNI | Length | Status code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
MBB Type: Type 1 (to be assigned by IANA)
Length: 1
Status code: 1 = MBB request
2 = MBB ack
9.2. Tree Information Item
A TN packet contains one or more TreeInfo items that allows a Merge
Node to identify which tree(s) and interface(s) are effected by the
TN. The same encoding is used for DTN and UTN packets. Following
[RFC6388], mLDP will assign a unique Label to each upstream node per
MP-LSP. This label identifies the UMH AND the LSP. Since we are
using a label to identify the UMH and LSP, there is no need to define
a IPv4 and IPv6 specific encoding. The Label included in the DTN
MUST be taken from the RNI that was signalled for that tree. The
Label for UTN packets is the Local Label that was allocated for that
tree. The TreeInfo item has the following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | UMH-Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Reserved: This is a 12 bits filed, set to zero on sending, ignored
when received.
UMH-Label: This is a 20 bit field encoding MPLS Label of the UMH.
Figure 8: mLDP TreeInfo item
10. Acknowledgements
The authors would like to thank Stefan Olofsson, Javed Asghar and
Greg Sheperd for their comments on the draft.
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11. IANA Considerations
IANA is requested to allocate UDP port numbers to TN messages. One
port number for TN in IP/PIM context, and another one for MPLS/mLDP
context. The separation of UDP port numbers between IP and MPLS is
requested to prevent problems when a PIM multicast tree is
transported partly through an mLDP multicast tree.
IANA is requested to allocate a value from "PIM Join Attribute" to
make routers capable to advertisement their Tree Notification
capability.
IANA is requested to allocate a value from "PIM Join Attribute Types"
for TN's join command extra information.
A new IANA registry is needed for "TN option TLVs". This describes
the types of TLVs containing extra options for TN messages.
12. Security Considerations
Two types of security problems can be foreseen by the authors:
o Handling illegally injected TN packets
o Handling replay attacks (re-injecting previous TN messages)
o TN messages propagating outside an operator's domain
Illegal TN packets can be detected with authentication check.
Providing authentication for TN messages is described in Section 6.
Prevention of replay attacks needs authentication in combination with
sequence numbering, which is also described at the same section.
Preventing TN messages that travel inline with data packets MUST be
solved by nodes egressing the operator's domain. Solutions for IP
and MPLS are described in sections Section 8 and Section 9,
respectively.
13. References
13.1. Normative References
[I-D.karan-mofrr]
Karan, A., Filsfils, C., Farinacci, D., Decraene, B.,
Leymann, N., and W. Henderickx, "Multicast only Fast Re-
Route", draft-karan-mofrr-02 (work in progress),
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March 2012.
[RFC5384] Boers, A., Wijnands, I., and E. Rosen, "The Protocol
Independent Multicast (PIM) Join Attribute Format",
RFC 5384, November 2008.
[RFC6388] Wijnands, IJ., Minei, I., Kompella, K., and B. Thomas,
"Label Distribution Protocol Extensions for Point-to-
Multipoint and Multipoint-to-Multipoint Label Switched
Paths", RFC 6388, November 2011.
13.2. Informative References
[I-D.atlas-rtgwg-mrt-mc-arch]
Atlas, A., Kebler, R., Wijnands, I., Csaszar, A., and G.
Envedi, "An Architecture for Multicast Protection Using
Maximally Redundant Trees",
draft-atlas-rtgwg-mrt-mc-arch-02 (work in progress),
July 2013.
Authors' Addresses
IJsbrand Wijnands (editor)
Cisco
De kleetlaan 6a
Diegem, 1831
Belgium
Phone:
Email: ice@cisco.com
Luc De Ghein
Cisco
De kleetlaan 6a
Diegem, 1831
Belgium
Phone:
Email: ldeghein@cisco.com
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Gabor Sandor Enyedi (editor)
Ericsson
Konyves Kalman Krt 11/B
Budapest, 1097
Hungary
Phone:
Email: Gabor.Sandor.Enyedi@ericsson.com
Andras Csaszar
Ericsson
Konyves Kalman Krt 11/B
Budapest, 1097
Hungary
Phone:
Email: Andras.Csaszar@ericsson.com
Jeff Tantsura
Ericsson
300 Holger Way
San Jose, California 95134
USA
Email: Jeff.Tantsura@ericsson.com
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