RFC 7275
Inter-Chassis Communication Protocol for Layer 2 Virtual Private Network (L2VPN) Provider Edge (PE) Redundancy
Pages: 83
Proposed Standard
Proposed Standard
Part 2 of 4 – Pages 11 to 35
4. ICC LDP Protocol Extension Specification
To address the requirements identified in the previous section, ICCP is modeled to comprise three layers: i. Application Layer: This provides the interface to the various redundancy applications that make use of the services of ICCP. ICCP is concerned with defining common connection management procedures and the formats of the messages exchanged at this layer; however, beyond that, it does not impose any restrictions
on the procedures or state machines of the clients, as these are
deemed application specific and lie outside the scope of ICCP.
This guarantees implementation interoperability without placing
any unnecessary constraints on internal design specifics.
ii. Inter-Chassis Communication (ICC) Layer: This layer implements
the common set of services that ICCP offers to the client
applications. It handles protocol versioning, RG membership,
Redundant Object identification, PE node identification, and
ICCP connection management.
iii. Transport Layer: This layer provides the actual ICCP message
transport. It is responsible for addressing, route resolution,
flow control, reliable and in-order message delivery,
connectivity resiliency/redundancy, and, finally, PE node
failure detection. The Transport layer may differ, depending on
the Physical Layer of the interconnect.
4.1. LDP ICCP Capability Advertisement
When an RG is enabled on a particular PE, an LDP session to every
remote PE in that RG MUST be created, if one does not already exist.
The capability of supporting ICCP MUST then be advertised to all of
those LDP peers in that RG. This is achieved by using the methods
described in [RFC5561] and advertising the "ICCP capability TLV". If
an LDP peer supports the dynamic capability advertisement, this can
be done by sending a new capability message with the S-bit set for
the "ICCP capability TLV" when the first RG is enabled on the PE. If
the peer does not support dynamic capability advertisements, then the
"ICCP TLV" MUST be included in the LDP initialization procedures in
the capability parameter [RFC5561].
4.2. RG Membership Management
ICCP defines a mechanism that enables PE nodes to manage their RG
membership. When a PE is configured to be a member of an RG, it will
first advertise the ICCP capability to its peers. Subsequently, the
PE sends an "RG Connect" message to the peers that have also
advertised ICCP capability. The PE then waits for the peers to send
their own "RG Connect" messages, if they haven't done so already.
For a given RG, the ICCP connection between two devices is considered
to be operational only when both devices have sent and received ICCP
"RG Connect" messages for that RG.
If a PE that has sent a particular "RG Connect" message doesn't
receive a corresponding RG Connect (or a Notification message
rejecting the connection) from a destination, it will remain in a
state of expecting the corresponding "RG Connect" message (or
Notification message). The RG will not become operational until the corresponding "RG Connect" message has been received. If a PE that has sent an "RG Connect" message receives a Notification message rejecting the connection, with a NAK TLV (Negative Acknowledgement TLV) (Section 6.4.1), it will stop attempting to bring up the ICCP connection immediately. A device MUST reject an incoming "RG Connect" message if at least one of the following conditions is satisfied: i. the PE is not a member of the RG; ii. the maximum number of simultaneous ICCP connections that the PE can handle is exceeded. Otherwise, the PE MUST bring up the connection by responding to the incoming "RG Connect" message with an appropriate RG Connect. A PE sends an "RG Disconnect" message to tear down the ICCP connection for a given RG. This is a unilateral operation and doesn't require any acknowledgement from the other PEs. Note that the ICCP connection for an RG MUST be operational before any client application can make use of ICCP services in that RG.4.2.1. ICCP Connection State Machine
A PE maintains an ICCP Connection state machine instance for every ICCP connection with a remote peer in the RG. This state machine is separate from any Application Connection state machine (Section 4.4.2). The ICCP Connection state machine reacts only to "RG Connect", "RG Disconnect", and "RG Notification" messages that do not contain any "Application TLVs". Actions and state transitions in the Application Connection state machines have no effect on the ICCP Connection state machine. The ICCP Connection state machine is defined to have six states, as follows: - NONEXISTENT: This state is the starting point for the state machine. It indicates that no ICCP connection exists and that there's no LDP session established between the PEs. - INITIALIZED: This state indicates that an LDP session exists between the PEs but LDP ICCP capability information has not yet been exchanged between them.
- CAPSENT: This state indicates that an LDP session exists between
the PEs and that the local PE has advertised LDP ICCP capability to
its peer.
- CAPREC: This state indicates that an LDP session exists between the
PEs and that the local PE has both received and advertised LDP ICCP
capability from/to its peer.
- CONNECTING: This state indicates that the local PE has initiated an
ICCP connection to its peer and is awaiting its response.
- OPERATIONAL: This state indicates that the ICCP connection is
operational.
The state transition table and state transition diagram follow.
ICCP Connection State Transition Table
STATE EVENT NEW STATE
--------------------------------------------------------------------
NONEXISTENT LDP session established INITIALIZED
INITIALIZED Transmit LDP ICCP capability CAPSENT
Receive LDP ICCP capability CAPREC
Action: Transmit LDP ICCP capability
LDP session torn down NONEXISTENT
CAPSENT Receive LDP ICCP capability CAPREC
LDP session torn down NONEXISTENT
CAPREC Transmit RG Connect message CONNECTING
Receive acceptable RG Connect message OPERATIONAL
Action: Transmit RG Connect message
Receive any other ICCP message CAPREC
Action: Transmit NAK TLV in RG
Notification message
LDP session torn down NONEXISTENT
CONNECTING Receive acceptable RG Connect message OPERATIONAL
Receive any other ICCP message CAPREC
Action: Transmit NAK TLV in RG
Notification message
LDP session torn down NONEXISTENT
OPERATIONAL Receive acceptable RG Disconnect message CAPREC
Transmit RG Disconnect message CAPREC
LDP session torn down NONEXISTENT
ICCP Connection State Transition Diagram
+------------+
| |
+------------------>|NONEXISTENT | LDP session torn down
| | |<--------------------------+
| +------------+ |
| LDP session | ^ LDP session |
| established | | torn down |
| V | |
| +-----------+ |
LDP | | | Tx LDP ICCP |
session| |INITIALIZED| capability |
torn | +---| |---------------+ |
down | Rx other | +-----------+ | |
| ICCP msg/ |Rx LDP ICCP | |
| Tx NAK TLV | capability/ | |
| +---+ |Tx LDP ICCP capability | |
| | | | | |
| V | V V |
| +-----------+ Rx LDP ICCP +--------+ |
+---| | capability | | |
|CAPREC |<----------------------|CAPSENT |---------->+
+---| |-------------------+ | | |
| +-----------+ | +--------+ |
| ^ ^ | |
Tx | | | | |
RG | | |Rx RG Disconnect msg | |
Connect| | | or |Rx RG Connect msg/ |
msg | | |Tx RG Disconnect msg | Tx RG Connect msg |
| | | V |
| | | +------------+ |
| | +--------------------| | |
| | |OPERATIONAL |------------>+
| | | | |
| |Rx other ICCP msg/ +------------+ |
| | Tx NAK TLV ^ |
| | | |
| +----------+ Rx RG Connect msg | |
| | |---------------------+ |
+----->|CONNECTING| |
| |----------------------------------------->+
+----------+
4.3. Redundant Object Identification
ICCP offers its client applications a uniform mechanism for identifying links, ports, forwarding constructs, and, more generally, objects (e.g., interfaces, pseudowires, VLANs) that are being protected in a redundant setup. These are referred to as Redundant Objects (ROs). An example of an RO is a multi-chassis link- aggregation group that spans two PEs. ICCP introduces a 64-bit opaque identifier to uniquely identify ROs in an RG. This identifier, referred to as the Redundant Object ID (ROID), MUST match between RG members for the protected object in question; this allows separate systems in an RG to use a common handle to reference the protected entity, irrespective of its nature (e.g., physical or virtual) and in a manner that is agnostic to implementation specifics. Client applications that need to synchronize state pertaining to a particular RO SHOULD embed the corresponding ROID in their TLVs.4.4. Application Connection Management
ICCP provides a common set of procedures by which applications on one PE can connect to their counterparts on another PE, for the purpose of inter-chassis communication in the context of a given RG. The prerequisite for establishing an Application Connection is to have an operational ICCP RG connection between the two endpoints. It is assumed that the association of applications with RGs is known a priori, e.g., by means of device configuration. ICCP then sends an "Application Connect TLV" (carried in an "RG Connect" message), on behalf of each client application, to each remote PE within the RG. The client may piggyback application-specific information in that "Connect TLV", which, for example, can be used to negotiate parameters or attributes prior to bringing up the actual Application Connection. The procedures for bringing up the Application Connection are similar to those of the ICCP connection: an Application Connection between two nodes is up only when both nodes have sent and received "RG Connect" messages with the proper "Application Connect TLVs". A PE MUST send a Notification message to reject an Application Connection request if one of the following conditions is encountered: i. the application doesn't exist or is not configured for that RG; ii. the Application Connection count exceeds the PE's capabilities.
When a PE receives such a rejection notification, it MUST stop attempting to bring up the Application Connection until it receives a new Application Connection request from the remote PE. This is done by responding to the incoming "RG Connect" message (carrying an "Application Connect TLV") with an appropriate "RG Connect" message (carrying a corresponding "Application Connect TLV"). When an application is stopped on a device or it is no longer associated with an RG, it MUST signal ICCP to trigger sending an "Application Disconnect TLV" (in the "RG Disconnect" message). This is a unilateral notification to the other PEs within an RG and as such doesn't trigger any response.4.4.1. Application Versioning
During Application Connection setup, a given application on one PE can negotiate with its counterpart on a peer PE the proper application version to use for communication. If no common version is agreed upon, then the Application Connection is not brought up. This is achieved through the following set of rules: - If an application receives an "Application Connect TLV" with a version number that is higher than its own, it MUST send a Notification message with a "NAK TLV" indicating status code "Incompatible Protocol Version" and supplying the version that is locally supported by the PE. - If an application receives an "Application Connect TLV" with a version number that is lower than its own, it MAY respond with an RG Connect that has an "Application Connect TLV" using the same version that was received. Alternatively, the application MAY respond with a Notification message to reject the request using the "Incompatible Protocol Version" code and supply the version that is supported. This allows an application to operate in either backwards-compatible or incompatible mode. - If an application receives an "Application Connect TLV" with a version that is equal to its own, then the application MUST honor or reject the request based on whether the application is configured for the RG in question, and whether or not the Application Connection count has been exceeded.
4.4.2. Application Connection State Machine
A PE maintains one Application Connection state machine instance per ICCP application for every ICCP connection with a remote PE in the RG. Each application's state machine reacts only to the "RG Connect", "RG Disconnect", and "RG Notification" messages that contain an "Application TLV" specifying that particular application. The Application Connection state machine has six states, as follows: - NONEXISTENT: This state indicates that the Application Connection does not exist, since there is no ICCP connection between the PEs. - RESET: This state indicates that an ICCP connection is operational between the PEs but that the Application Connection has not been initialized yet or has been resent. - CONNSENT: This state indicates that the local PE has requested initiation of an Application Connection with its peer but has not received a response yet. - CONNREC: This state indicates that the local PE has received a request to initiate an Application Connection from its peer but has not responded yet. - CONNECTING: This state indicates that the local PE has transmitted to its peer an "Application Connection" message with the A-bit set to 1 and is awaiting the peer's response. - OPERATIONAL: This state indicates that the Application Connection is operational. The state transition table and state transition diagram follow. ICCP Application Connection State Transition Table STATE EVENT NEW STATE ------------------------------------------------------------------- NONEXISTENT ICCP connection established RESET RESET ICCP connection torn down NONEXISTENT Transmit Application Connect TLV CONNSENT Receive Application Connect TLV CONNREC Receive any other Application TLV RESET Action: Transmit NAK TLV
CONNSENT Receive NAK TLV RESET
Receive Application Connect TLV OPERATIONAL
with A-bit=1
Action: Transmit Application Connect
TLV with A-bit=1
Receive any other Application TLV RESET
Action: Transmit NAK TLV
ICCP connection torn down NONEXISTENT
CONNREC Transmit NAK TLV RESET
Transmit Application Connect TLV CONNECTING
with A-bit=1
Receive Application Connect TLV CONNREC
Receive any Application TLV except RESET
Connect
Action: Transmit NAK TLV
ICCP connection torn down NONEXISTENT
CONNECTING Receive Application Connect TLV OPERATIONAL
with A-bit=1
Receive any other Application TLV RESET
Action: Transmit NAK TLV
ICCP connection torn down NONEXISTENT
OPERATIONAL Receive Application Disconnect TLV RESET
Transmit Application Disconnect TLV RESET
ICCP connection torn down NONEXISTENT
ICCP Application Connection State Transition Diagram
+------------+
| |
+---------------->|NONEXISTENT | ICCP connection torn down
| | |<--------------------------+
| +------------+ |
| ICCP connection| ^ ICCP connection |
| established | | torn down |
| | | |
| V | Rx other App TLV/ |
| +-----------+<-----+ Tx NAK TLV |
ICCP | Rx App | | | |
connect| Connect TLV | RESET |------+ |
torn | +-------------| |---------------+ |
down | | +-----------+ Tx App | |
| | ^ ^ ^ ^ Connect TLV| |
| | Tx NAK | | | | | |
| | or | | | | | |
| | Rx non- | | | | | |
| | Connect | | | | | |
| V TLV/Tx NAK | | |Rx NAK TLV V |
| +-----------+ | | | |or +--------+ |
+-| |---+ | | +---------| | |
|CONNREC | | | Rx other |CONNSENT|---------->+
+-| |-+ | | App TLV/ | | |
| +-----------+ | | | Tx NAK +--------+ |
| ^---+ | | |Rx App Connect |
| Rx App | | |TLV (A=1)/ |
| Connect TLV | |Rx App Disconn | Tx App |
| | |or | Connect TLV |
| Tx App Connect | |Tx App Disconn V (A=1) |
| TLV (A=1) | | +------------+ |
| | +------| | |
| Rx other App | |OPERATIONAL |------------>+
| TLV/Tx NAK | | | |
| +------+ +------------+ |
| | ^ Rx App Connect |
| +----------+ | TLV (A=1) |
| | |---------------------+ |
+--->|CONNECTING| |
| |----------------------------------------->+
+----------+
4.5. Application Data Transfer
When an application has information to transfer over ICCP, it triggers the transmission of an "Application Data" message. ICCP guarantees in-order and lossless delivery of data. An application may reject a message or a set of one or more TLVs within a message by using the Notification message with a "NAK TLV". Furthermore, an application may implement its own ACK mechanism, if deemed required, by defining an application-specific TLV to be transported in an "Application Data" message. Note that this document does not define a common ACK mechanism for applications. It is left up to the application to define the procedures to handle the situation where a PE receives a "NAK TLV" in response to a transmitted "Application Data" message. Depending on the specifics of the application, it may be favorable to have the PE that sent the NAK explicitly request retransmission of data. On the other hand, for certain applications it may be more suitable to have the original sender of the "Application Data" message handle retransmissions in response to a NAK. ICCP supports both models.4.6. Dedicated Redundancy Group LDP Session
For certain ICCP applications, it is required that a fairly large amount of RG information be exchanged in a very short period of time. In order to better distribute the load in a multiple-processor system, and to avoid head-of-line blocking to other LDP applications, initiating a separate TCP/IP session between the two LDP speakers may be required. This procedure is OPTIONAL and does not change the operation of LDP or ICCP. A PE that requires a separate LDP session will advertise a separate LDP adjacency with a non-zero label space identifier. This will cause the remote peer to open a separate LDP session for this label space. No labels need to be advertised in this label space, as it is only used for one or a set of ICCP RGs. All relevant LDP and ICCP procedures still apply as described in [RFC5036] and this document.5. ICCP PE Node Failure / Isolation Detection Mechanism
ICCP provides its client applications a notification when a remote PE that is a member of the RG is no longer reachable. In the case of a dedicated interconnect, this indicates that the remote PE node has failed, whereas in the case of a shared interconnect this indicates that the remote PE node has either failed or become isolated from the MPLS network. This information is used by the client applications to
trigger failover according to the procedures of the redundancy
protocol employed on the AC and PW. To that end, ICCP does not
define its own Keep-Alive mechanism for the purpose of monitoring the
health of remote PE nodes but rather reuses existing fault detection
mechanisms. The following mechanisms may be used by ICCP to detect
PE node failure:
- Bidirectional Forwarding Detection (BFD)
Run a BFD session [RFC5880] between the PEs that are members of a
given RG, and use that to detect PE node failure. This assumes
that resiliency mechanisms are in place to protect connectivity to
the remote PE nodes, and hence loss of BFD periodic messages from a
given PE node can only mean that the node itself has failed.
- IP Reachability Monitoring
It is possible for a PE to monitor IP-layer connectivity to other
members of an RG that are participating in IGP/BGP. When
connectivity to a given PE is lost, the local PE interprets that to
mean loss of the remote PE node. This technique assumes that
resiliency mechanisms are in place to protect the route to the
remote PE nodes, and hence loss of IP reachability to a given node
can only mean that the node itself has failed.
It is worth noting here that loss of the LDP session with a PE in an
RG is not a reliable indicator that the remote PE itself is down. It
is possible, for example, that the remote PE could encounter a local
event that would lead to resetting the LDP session, while the PE node
would remain operational for traffic forwarding purposes.
6. ICCP Message Formats
This section defines the messages exchanged at the Application and
ICC layers.
6.1. Encoding ICC into LDP Messages
ICCP requires reliable, in-order, stateful message delivery, as well
as capability negotiation between PEs. LDP offers all of these
features and is already in wide use in the applications that would
also require the ICCP protocol extensions. For these reasons, ICCP
takes advantage of the already-defined LDP protocol infrastructure.
[RFC5036], Section 3.5 defines a generic LDP message structure. A
new set of LDP message types is defined to communicate the ICCP
information. LDP message types in the range 0x0700 to 0x070F will be
used for ICCP.
Message types have been allocated by IANA; see Section 12 below for details.6.1.1. ICC Header
Every ICCP message comprises an ICC-specific LDP Header followed by message data. The format of the ICC Header 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |U| Message Type | Message Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Message ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 0x0005 (ICC RG ID) | Length=4 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ICC RG ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | Mandatory ICC Parameters | ~ ~ + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | Optional ICC Parameters | ~ ~ + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - U-bit Unknown message bit. Upon receipt of an unknown message, if U is clear (=0), a notification is returned to the message originator; if U is set (=1), the unknown message is silently ignored. Subsequent sections that define messages specify a value for the U-bit. - Message Type Identifies the type of the ICCP message. Must be in the range 0x0700 to 0x070F.
- Message Length
2-octet integer specifying the total length of this message in
octets, excluding the "U-bit", "Message Type", and "Length" fields.
- Message ID
4-octet value used to identify this message. Used by the sending
PE to facilitate identifying "RG Notification" messages that may
apply to this message. A PE sending an "RG Notification" message
in response to this message SHOULD include this Message ID in the
"NAK TLV" of the "RG Notification" message; see Section 6.4.
- ICC RG ID TLV
A TLV of type 0x0005, length 4, containing a 4-octet unsigned
integer designating the Redundancy Group of which the sending
device is a member. RG ID value 0x00000000 is reserved by the
protocol.
- Mandatory ICC Parameters
Variable-length set of required message parameters. Some messages
have no required parameters.
For messages that have required parameters, the required parameters
MUST appear in the order specified by the individual message
specifications in the sections that follow.
- Optional ICC Parameters
Variable-length set of optional message parameters. Many messages
have no optional parameters.
For messages that have optional parameters, the optional parameters
may appear in any order.
6.1.2. ICC Parameter Encoding
The generic format of an ICC parameter 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |U|F| Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | TLV(s) | ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - U-bit Unknown TLV bit. Upon receipt of an unknown TLV, if U is clear (=0), a notification MUST be returned to the message originator and the entire message MUST be ignored; if U is set (=1), the unknown TLV MUST be silently ignored and the rest of the message processed as if the unknown TLV did not exist. Subsequent sections that define TLVs specify a value for the U-bit. - F-bit Forward unknown TLV bit. This bit applies only when the U-bit is set and the LDP message containing the unknown TLV is to be forwarded. If F is clear (=0), the unknown TLV is not forwarded with the LDP message; if F is set (=1), the unknown TLV is forwarded with the LDP message. Subsequent sections that define TLVs specify a value for the F-bit. By setting both the U- and F-bits, a TLV can be propagated as opaque data through nodes that do not recognize the TLV. - Type 14 bits indicating the ICC Parameter type. - Length Length of the TLV in octets, excluding the "U-bit", "F-bit", "Type", and "Length" fields. - TLV(s): A set of 0 or more TLVs. Contents will vary according to the message type.
6.1.3. Redundant Object Identifier Encoding
The Redundant Object Identifier (ROID) is a generic opaque handle that uniquely identifies a Redundant Object (e.g., link, bundle, VLAN) that is being protected in an RG. It is encoded 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ROID | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ where the ROID is an 8-octet field encoded as an unsigned integer. The ROID value of 0 is reserved. The ROID is carried within application-specific TLVs.6.2. RG Connect Message
The "RG Connect" message is used to establish the ICCP RG connection in addition to individual Application Connections between PEs in an RG. An "RG Connect" message with no "Application Connect TLV" signals establishment of the ICCP RG connection, whereas an "RG Connect" message with a valid "Application Connect TLV" signals the establishment of an Application Connection in addition to the ICCP RG connection if the latter is not already established. An implementation MAY send a dedicated "RG Connect" message to set up the ICCP RG connection and a separate "RG Connect" message for each client application. However, all implementations MUST support the receipt of an "RG Connect" message that triggers the setup of the ICCP RG connection as well as a single Application Connection simultaneously. A PE sends an "RG Connect" message to declare its membership in a Redundancy Group. One such message should be sent to each PE that is a member of the same RG. The set of PEs to which "RG Connect" messages should be transmitted is known via configuration or an auto- discovery mechanism that is outside the scope of this specification. If a device is a member of multiple RGs, it MUST send separate "RG Connect" messages for each RG even if the receiving device(s) happens to be the same.
The format of the "RG Connect" message is as follows:
i. ICC Header with Message type = "RG Connect Message" (0x0700)
ii. ICC Sender Name TLV
iii. Zero or one "Application Connect TLV"
The currently defined "Application Connect TLVs" are as follows:
- PW-RED Connect TLV (Section 7.1.1)
- mLACP Connect TLV (Section 7.2.1)
The details of these TLVs are discussed in Section 7.
The "RG Connect" message can contain zero or one "Application Connect
TLV".
6.2.1. ICC Sender Name TLV
The "ICC Sender Name TLV" carries the hostname of the sender, encoded
in UTF-8 [RFC3629] format. This is used primarily for the purpose of
management of the RG and easing network operations. The specific
format is shown below:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Type = 0x0001 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Name |
+ +-+-+-+-+-+-+-+-+-+
~ ~
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- U=F=0
- Type
Set to 0x0001 (from the ICC parameter name space).
- Length
Length of the TLV in octets, excluding the "U-bit", "F-bit",
"Type", and "Length" fields.
- Sender Name
An administratively assigned name of the sending device, encoded in
UTF-8 format and limited to a maximum of 80 octets. This field
does not include a terminating null character.
6.3. RG Disconnect Message
The "RG Disconnect" message serves a dual purpose: to signal that a
particular Application Connection is being closed within an RG or
that the ICCP RG connection itself is being disconnected because the
PE wishes to leave the RG. The format of this message 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U| Message Type = 0x0701 | Message Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 0x0005 (ICC RG ID) | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ICC RG ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Disconnect Code TLV |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Optional Application Disconnect TLV |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Optional Parameter TLVs |
+ +
| |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- U-bit
U=0
- Message Type
The message type for the "RG Disconnect" message is set to 0x0701.
- Length
Length of the TLV in octets, excluding the "U-bit", "Message Type",
and "Message Length" fields.
- Message ID
Defined in Section 6.1.1 above.
- ICC RG ID
Defined in Section 6.1.1 above.
- Disconnect Code TLV
The format of this 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Type = 0x0004 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ICCP Status Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- U-bit and F-bit
Both are set to 0.
- Type
Set to "Disconnect Code TLV" (0x0004).
- Length
Length of the TLV in octets, excluding the "U-bit", "F-bit",
"Type", and "Length" fields.
- ICCP Status Code
A status code that reflects the reason for the disconnect
message. Allowed values are "ICCP RG Removed" and "ICCP
Application Removed from RG".
- Optional Application Disconnect TLV
Zero or one "Application Disconnect TLV" (defined in Sections 7.1.2
and 7.2.2). If the "RG Disconnect" message has a status code of
"RG Removed", then it MUST NOT contain any "Application Disconnect
TLVs", as the sending PE is signaling that it has left the RG and
thus is disconnecting the ICCP RG connection with all associated
client Application Connections. If the message has a status code
of "Application Removed from RG", then it MUST contain exactly one
"Application Disconnect TLV", as the sending PE is only tearing
down the connection for the specified application. Other
applications, and the ICCP RG connection, are not to be affected.
- Optional Parameter TLVs
None are defined for this message in this document. This is
specified to allow for future extensions.
6.4. RG Notification Message
A PE sends an "RG Notification" message to indicate one of the
following: to reject an ICCP connection, to reject an Application
Connection, to reject an entire message, or to reject one or more
TLVs within a message. The Notification message MUST only be sent to
a PE that is already part of an RG.
The "RG Notification" message MUST only be used to reject messages or
TLVs corresponding to a single ICCP application. In other words,
there is a limit of at most a single ICCP application per "RG
Notification" message.
The format of the "RG Notification" message is as follows:
i. ICC Header with Message type = "RG Notification Message" (0x0702)
ii. Notification Message TLVs
The currently defined Notification message TLVs are as follows:
i. ICC Sender Name TLV
ii. Negative Acknowledgement (NAK) TLV
6.4.1. Notification Message TLVs
The "ICC Sender Name TLV" uses the same format as the format used in the "RG Connect" message and was described above. The "NAK TLV" is defined 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |U|F| Type = 0x0002 | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ICCP Status Code | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Rejected Message ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Optional TLV(s) | + + | | ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - U-bit and F-bit Both are set to 0. - Type Set to "NAK TLV" (0x0002). - Length Length of the TLV in octets, excluding the "U-bit", "F-bit", "Type", and "Length" fields. - ICCP Status Code A status code that reflects the reason for the "NAK TLV". Allowed values are as follows: i. Unknown ICCP RG (0x00010001) This code is used to reject a new incoming ICCP connection for an RG that is not configured on the local PE. When this code is used, the "Rejected Message ID" field MUST contain the message ID of the rejected "RG Connect" message.
ii. ICCP Connection Count Exceeded (0x00010002)
This is used to reject a new incoming ICCP connection that
would cause the local PE's ICCP connection count to exceed its
capabilities. When this code is used, the "Rejected Message
ID" field MUST contain the message ID of the rejected "RG
Connect" message.
iii. ICCP Application Connection Count Exceeded (0x00010003)
This is used to reject a new incoming Application Connection
that would cause the local PE's ICCP connection count to
exceed its capabilities. When this code is used, the
"Rejected Message ID" field MUST contain the message ID of the
rejected "RG Connect" message and the corresponding
"Application Connect TLV" MUST be included in the "Optional
TLV".
iv. ICCP Application not in RG (0x00010004)
This is used to reject a new incoming Application Connection
when the local PE doesn't support the application or the
application is not configured in the RG. When this code is
used, the "Rejected Message ID" field MUST contain the message
ID of the rejected "RG Connect" message and the corresponding
"Application Connect TLV" MUST be included in the "Optional
TLV".
v. Incompatible ICCP Protocol Version (0x00010005)
This is used to reject a new incoming Application Connection
when the local PE has an incompatible version of the
application. When this code is used, the "Rejected Message
ID" field MUST contain the message ID of the rejected "RG
Connect" message and the corresponding "Application Connect
TLV" MUST be included in the "Optional TLV".
vi. ICCP Rejected Message (0x00010006)
This is used to reject an "RG Application Data" message, or
one or more TLVs within the message. When this code is used,
the "Rejected Message ID" field MUST contain the message ID of
the rejected "RG Application Data" message.
vii. ICCP Administratively Disabled (0x00010007)
This is used to reject any ICCP messages from a peer from
which the PE is not allowed to exchange ICCP messages due to
local administrative policy.
- Rejected Message ID
If non-zero, a 4-octet value that identifies the peer message to
which the "NAK TLV" refers. If zero, no specific peer message is
being identified.
- Optional TLV(s)
A set of one or more optional TLVs. If the status code is
"Rejected Message", then this field contains the TLV or TLVs that
were rejected. If the entire message is rejected, all of its TLVs
MUST be present in this field; otherwise, the subset of TLVs that
were rejected MUST be echoed in this field.
If the status code is "Incompatible Protocol Version", then this
field contains the original "Application Connect TLV" sent by the
peer, in addition to the "Requested Protocol Version TLV" defined
below:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Type = 0x0003 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Connection Reference | Requested Version |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- U-bit and F-bit
Both are set to 0.
- Type
Set to 0x0003 for "Requested Protocol Version TLV".
- Length
Length of the TLV in octets, excluding the "U-bit", "F-bit",
"Type", and "Length" fields.
- Connection Reference
Set to the "Type" field of the "Application Connect TLV" that was
rejected because of incompatible version.
- Requested Version
The version of the application supported by the transmitting
device. For this version of the protocol, it is set to 0x0001.
6.5. RG Application Data Message
The "RG Application Data" message is used to transport application
data between PEs within an RG. A single message can be used to carry
data from only one application. Multiple Application TLVs are
allowed in a single message, as long as all of these TLVs belong to
the same application. The format of the "Application Data" message
is as follows:
i. ICC Header with Message type = "RG Application Data Message"
(0x0703)
ii. Application-specific TLVs
The details of these TLVs are discussed in Section 7. All
application-specific TLVs in one "RG Application Data" message MUST
belong to a single application but MAY reference different ROs.
(page 35 continued on part 3)