RFC 2909
The Multicast Address-Set Claim (MASC) Protocol
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Network Working Group P. Radoslavov Request for Comments: 2909 D. Estrin Category: Experimental R. Govindan USC/ISI M. Handley ACIRI S. Kumar USC/ISI D. Thaler Microsoft September 2000 The Multicast Address-Set Claim (MASC) Protocol Status of this Memo This memo defines an Experimental Protocol for the Internet community. It does not specify an Internet standard of any kind. Discussion and suggestions for improvement are requested. Distribution of this memo is unlimited. Copyright Notice Copyright (C) The Internet Society (2000). All Rights Reserved.Abstract
This document describes the Multicast Address-Set Claim (MASC) protocol which can be used for inter-domain multicast address set allocation. MASC is used by a node (typically a router) to claim and allocate one or more address prefixes to that node's domain. While a domain does not necessarily need to allocate an address set for hosts in that domain to be able to allocate group addresses, allocating an address set to the domain does ensure that inter-domain group- specific distribution trees will be locally-rooted, and that traffic will be sent outside the domain only when and where external receivers exist.
Table of Contents
1 Introduction .................................................. 4 1.1 Terminology ................................................. 4 1.2 Definitions ................................................. 4 2 Requirements for Inter-Domain Address Allocation .............. 5 3 Overall Architecture .......................................... 5 3.1 Claim-Collide vs. Query-Response Rationale .................. 6 4 MASC Topology ................................................. 6 4.1 Managed vs Locally-Allocated Space .......................... 8 4.2 Prefix Lifetime ............................................. 8 4.3 Active vs. Deprecated Prefixes .............................. 9 4.4 Multi-Parent Sibling-to-Sibling and Internal Peering ........ 9 4.5 Administratively-Scoped Address Allocation .................. 9 5 Protocol Details .............................................. 10 5.1 Claiming Space .............................................. 10 5.1.1 Claim Comparison Function ................................. 12 5.2 Renewing an Existing Claim .................................. 12 5.3 Expanding an Existing Prefix ................................ 12 5.4 Releasing Allocated Space ................................... 13 6 Constants ..................................................... 13 7 Message Formats ............................................... 14 7.1 Message Header Format ....................................... 14 7.2 OPEN Message Format ......................................... 15 7.3 UPDATE Message Format ....................................... 17 7.4 KEEPALIVE Message Format .................................... 21 7.5 NOTIFICATION Message Format ................................. 21 8 MASC Error Handling ........................................... 24 8.1 Message Header Error Handling ............................... 24 8.2 OPEN Message Error Handling ................................. 25 8.3 UPDATE Message Error Handling ............................... 26 8.4 Hold Timer Expired Error Handling ........................... 28 8.5 Finite State Machine Error Handling ......................... 28 8.6 NOTIFICATION Message Error Handling ......................... 28 8.7 Cease ....................................................... 29 8.8 Connection Collision Detection .............................. 29 9 MASC Version Negotiation ...................................... 30 10 MASC Finite State Machine .................................... 30 10.1 Open/Close MASC Connection FSM ............................. 31 11 UPDATE Message Processing .................................... 35 11.1 Accept/Reject an UPDATE .................................... 36 11.2 PREFIX_IN_USE Message Processing ........................... 38 11.2.1 PREFIX_IN_USE by PARENT .................................. 38 11.2.2 PREFIX_IN_USE by SIBLING ................................. 38 11.2.3 PREFIX_IN_USE by CHILD ................................... 38 11.2.4 PREFIX_IN_USE by INTERNAL_PEER ........................... 38 11.3 CLAIM_DENIED Message Processing ............................ 39 11.3.1 CLAIM_DENIED by CHILD or SIBLING ......................... 39
11.3.2 CLAIM_DENIED by INTERNAL_PEER ............................ 39 11.3.3 CLAIM_DENIED by PARENT ................................... 39 11.4 CLAIM_TO_EXPAND Message Processing ......................... 39 11.4.1 CLAIM_TO_EXPAND by PARENT ................................ 39 11.4.2 CLAIM_TO_EXPAND by SIBLING ............................... 40 11.4.3 CLAIM_TO_EXPAND by CHILD ................................. 40 11.4.4 CLAIM_TO_EXPAND by INTERNAL_PEER ......................... 40 11.5 NEW_CLAIM Message Processing ............................... 41 11.6 PREFIX_MANAGED Message Processing. ........................ 41 11.6.1 PREFIX_MANAGED by PARENT ................................. 41 11.6.2 PREFIX_MANAGED by CHILD or SIBLING ....................... 41 11.6.3 PREFIX_MANAGED by INTERNAL_PEER .......................... 41 11.7 WITHDRAW Message Processing ................................ 42 11.7.1 WITHDRAW by CHILD ........................................ 42 11.7.2 WITHDRAW by SIBLING ...................................... 42 11.7.3 WITHDRAW by INTERNAL ..................................... 42 11.7.4 WITHDRAW by PARENT ....................................... 43 11.8 UPDATE Message Ordering .................................... 43 11.8.1 Parent to Child .......................................... 43 11.8.2 Child to Parent .......................................... 44 11.8.3 Sibling to Sibling ....................................... 44 11.8.4 Internal to Internal ..................................... 44 12 Operational Considerations ................................... 45 12.1 Bootup Operations .......................................... 45 12.2 Leaf and Non-leaf MASC Domain Operation .................... 45 12.3 Clock Skew Workaround ...................................... 45 12.4 Clash Resolving Mechanism .................................. 46 12.5 Changing Network Providers ................................. 47 12.6 Debugging .................................................. 47 12.6.1 Prefix-to-Domain Lookup .................................. 47 12.6.2 Domain-to-Prefix Lookup .................................. 47 13 MASC Storage ................................................. 47 14 Security Considerations ...................................... 48 15 IANA Considerations .......................................... 48 16 Acknowledgments .............................................. 48 17 APPENDIX A: Sample Algorithms ................................ 49 17.1 Claim Size and Prefix Selection Algorithm .................. 49 17.1.1 Prefix Expansion ......................................... 49 17.1.2 Reducing Allocation Latency .............................. 50 17.1.3 Address Space Utilization ................................ 50 17.1.4 Prefix Selection After Increase of Demand ................ 50 17.1.5 Prefix Selection After Decrease of Demand ................ 51 17.1.6 Lifetime Extension Algorithm ............................. 51 18 APPENDIX B: Strawman Deployment .............................. 51 19 Authors' Addresses ........................................... 52 20 References ................................................... 54 21 Full Copyright Statement ..................................... 56
1. Introduction
This document describes MASC, a protocol for inter-domain multicast address set allocation. The MASC protocol (a Layer-3 protocol in the multicast address allocation architecture [MALLOC]) is used by a node (typically a router) to claim and allocate one or more address prefixes to that node's domain. Each prefix has an associated lifetime, and is chosen out of a larger prefix with a lifetime at least as long, in a manner such that prefixes are aggregatable. At any time, each MASC node (a Prefix Coordinator in [MALLOC]) will typically advertise several prefixes with different lifetimes and scopes, allowing Multicast Address Allocation Servers (MAAS's) in that domain or child MASC domains to choose appropriate addresses for their clients. The set of prefixes ("address set") associated with a domain is injected into an inter-domain routing protocol (e.g., BGP4+ [MBGP]), where it can be used by an inter-domain multicast tree construction protocol (e.g., BGMP [BGMP]) to construct inter-domain group-shared trees. Note that a domain does not need to allocate an address set for the hosts in that domain to be able to allocate group addresses, nor does allocating necessarily guarantee that hosts in other domains will not use an address in the set (since, for example, hosts are not forced to contact a MAAS before using a group address). Allocating an address set to a domain does, however, ensure that inter-domain group-specific multicast distribution trees for any group in the address set will be locally-rooted, and that traffic will be sent outside the given domain only when and where external receivers exist.1.1. Terminology
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 [RFC2119]. Constants used by this protocol are shown as [NAME_OF_CONSTANT], and summarized in Section 6.1.2. Definitions
This specification uses a number of terms that may not be familiar to the reader. This section defines some of these and refers to other documents for definitions of others.
MAAS (Multicast Address Allocation Server)
A host providing multicast address allocation services to end
users (e.g. via MADCAP [MADCAP]).
MASC server
A node running MASC.
Peer
Other MASC speakers a node directly communicates with.
Multicast
IP Multicast, as defined for IPv4 in [RFC1112] and for IPv6 in
[RFC2460].
Multicast Address
An IP multicast address or group address, as defined in [RFC1112]
and [RFC2373]. An identifier for a group of nodes.
2. Requirements for Inter-Domain Address Allocation
The key design requirements for the inter-domain address allocation
mechanism are:
o Efficient address space utilization when space is scare, which
naturally implies that address allocations be based on the actual
address usage patterns, and therefore that it be dynamic.
o Address aggregation, that implies that the address allocation
mechanism be hierarchical.
o Minimize flux in the allocated address sets (e.g. the address sets
should be reused when possible).
o Robustness, by using decentralized mechanisms.
The timeliness in obtaining an address set is not a major design
constraint as this is taken care of at a lower level [MALLOC].
3. Overall Architecture
The Multicast Address Set Claim (MASC) protocol is used by MASC
domains to claim and allocate address sets for use by Multicast
Address Allocation Servers (MAASs) within each domain. Typically one
or more border routers of each domain that requires multicast address
space of its own would run MASC. Throughout this document, the term
"MASC domain" refers to a domain that has at least one node running
MASC; typically these domains will be Autonomous Systems (AS's). A
MASC node (on behalf of its domain) chooses an address set to claim,
sends a claim to other MASC domains in the network, and waits while
listening for any colliding claims. If there is a collision, the
losing claimer gives up the colliding claim and claims a different
address set.
After a sufficiently long collision-free waiting period, the address
set chosen by a MASC node is considered allocated to that node's
domain. Three things may then happen:
a) The allocated prefix can then be injected as a "multicast route"
into the inter-domain routing protocol (e.g., BGP4+ [MBGP]) as
"G-RIB" Network Layer Reachability Information (NLRI), where it
may be used by an inter-domain multicast routing protocol (e.g.,
BGMP [BGMP]) to construct group-shared trees. To reduce the size
and slow the growth of the G-RIB, MASC nodes may perform CIDR-like
aggregation [CIDR] of the multicast NLRI information. This
motivates the need for an algorithm to select prefixes for domains
in such a way as to ensure good aggregation in addition to
achieving good address space utilization.
b) The node's domain may assign to itself a sub-prefix which can be
used by MAASs within the domain.
c) Sub-prefixes may be allocated to child domains, if any.
3.1. Claim-Collide vs. Query-Response Rationale
We choose a claim-collide mechanism instead of a query-response
mechanism for the following reasons. In a query-response mechanism,
replicas of the MASC node would be needed in parent MASC domains in
order to make their responses be robust to failures. This brings
about the associated problem of synchronization of the replicas and
possibly additional fragmentation of the address space. In addition,
even in this mechanism, address collisions would still need to be
handled. We believe the proposed claim-collide mechanism is simpler
and more robust than a query-response mechanism.
4. MASC Topology
The domain hierarchy used by MASC is congruent to the somewhat
hierarchical structure of the inter-domain topology, e.g., backbones
connected to regionals, regionals connected to metropolitan
providers, etc. As in BGP, MASC connections are locally configured.
A MASC domain that is a customer of other MASC domains will have one
or more of those provider domains as its parent. For example, a MASC
domain that is a regional provider will choose one (or more) of its
backbone provider domains as its parent(s). Children are configured
with their parent MASC domain, and parents are configured with their
children domains. At the top, a number of Top-Level Domains are
connected in a (sparse) mesh and share the global multicast address
space. To improve the robustness, a pair of children of the same
parent domain MAY be configured as siblings with regard to that
parent.
Figure 1 illustrates a sample topology. Double-line links denote
intra-domain TCP peering sessions, and single-line links denote
inter-domain TCP connections. T1 and T2 are Top-Level Domains (e.g.,
backbone providers), containing MASC speakers T1a and T2a,
respectively. P3 and P4 are regional domains, containing (P3a, P3b),
and (P4a, P4b) respectively. P3 has a single customer (or "child"),
C5, containing (C5a, C5b, C5c). P4 has three children, C5, C6, C7,
containing (C5a, C5b, C5c), (C6a, C6b), and (C7a) respectively.
T1a-----------T2a
| |
| |
| |
P3a====P3b P4a====P4b
| | / | / | \
| | _______/ | / | \
| | / | / | \______
| | / | / | \
C5a====C5b C6a====C6b----------C7a
\\ //
\\//
C5c
Figure 1: Example MASC Topology
All MASC communications use TCP. Each MASC node is connected to and
communicates directly with other MASC nodes. The local node acts in
exactly one of the following four roles with respect to each remote
note:
INTERNAL_PEER
The local and remote nodes are both in the same MASC domain. For
example, P4b is an INTERNAL_PEER of P4a.
CHILD
A customer relationship exists whereby the local node may obtain
address space from the remote node. For example, C6a is a CHILD
in its session with P4a.
PARENT
A provider relationship exists whereby the remote node may obtain
address space from the local node. For example, T2a is a PARENT
in its session with P4a. Whether space is actually requested is
up to the implementation and local policy configuration.
SIBLING
No customer-provider relationship exists. For example, T2a is a
SIBLING in its session with T1a (Top-Level Domain SIBLING
peering). Also, C6b is a SIBLING in its session with C7a with
regard to their common parent P4.
A node's message will be propagated to its parent, all siblings with
the same parent, and its children. Since a domain need not have a
direct peering session with every sibling, a MASC domain must
propagate messages from a child domain to other children, can
propagate messages from a parent domain to other siblings, and, if a
Top-Level Domain, it must propagate messages from a sibling to other
siblings, otherwise may propagate messages from a sibling domain to
its parent and other siblings.
4.1. Managed vs Locally-Allocated Space
Each domain has a "Managed" Address Set, and a "Locally-Allocated"
Address Set. The "managed" space includes all address space which a
domain has successfully claimed via MASC. The "locally-allocated"
space, on the other hand, includes all address space which MAASs
inside the domain may use. Thus, the locally-allocated space is a
subset of the managed space, and refers to the portion which a domain
allocates for its own use.
For leaf domains (ones with no children), these two sets are
identical, since all claimed space is allocated for local use. A
parent domain, on the other hand, "manages" all address space which
it has claimed via MASC, while sub-prefixes can be allocated to
itself and to its children.
4.2. Prefix Lifetime
Each prefix has an associated lifetime. If a domain wants to use a
prefix longer than its lifetime, that domain must "renew" the prefix
BEFORE its lifetime expires (see Section 5.2). If the lifetime
cannot be extended, then the domain should either retry later to
extend, or should choose and claim another prefix.
After a prefix's lifetime expires, MASC nodes in the domain that own that prefix must stop using that prefix. The corresponding entry from the G-RIB database must be removed, and all information associated with the expired prefix may be deleted from the MASC node's local memory.4.3. Active vs. Deprecated Prefixes
Each prefix advertised by a parent to its children can be either "active" or "deprecated". A "deprecated" prefix is a prefix that the parent wishes to discontinue to use after its lifetime expires. The "active" prefixes only are candidates for size expansion or lifetime extension. Usually, this information will be used by a child as a hint to know which of the parent's prefixes might have their lifetime extended.4.4. Multi-Parent Sibling-to-Sibling and Internal Peering
Two sibling nodes that have more than one common parent will create and use between them a number of transport-level connections, one per each common parent. The information associated with a parent will be sent over the connection that corresponds to the same parent. Internal peers do not need to open multiple connections between them; a single connection is used for all information.4.5. Administratively-Scoped Address Allocation
MASC can also be used for sub-allocating prefixes of addresses within an administrative scope zone [SCOPE], but only if the scope is "divisible" (as described in [MALLOC] and [MZAP]). A MASC node can learn what scopes it resides within by listening to MZAP [MZAP] messages. A "Zone TLD" is a domain which has no parent domain within the scope zone. Zone TLDs act as TLDs for the prefix associated with the scope. Figure 2 gives an example, where a scope boundary around domains P3 and C5 has been added to Figure 1. Domain P3 is a Zone TLD, since its only parent (T1) is outside the boundary. Hence, P3 can claim space directly out of the prefix associated with the scope itself. Domain C5, on the other hand, has a parent within the scope (namely, P3), and hence is not a Zone TLD.
T1a-----------T2a
| |
............|....... |
. | . |
. P3a====P3b . P4a
. | | . /
. | | _______/
. | | / .
. | | / .
. C5a====C5b .
. \\ // .
. \\// .
. C5c .
. .
. Admin Scope Zone .
....................
Figure 2: Scope Zone Example
It is assumed that the role of a node (as discussed in Section 4)
with respect to a given peering session is the same for every scope
in which both ends are contained. A peering session that crosses a
scope boundary (such as the session between C5b and P4a in Figure 2)
is ignored when propagating messages that pertain to the given scope.
That is, such messages are not sent across such sessions.
5. Protocol Details
5.1. Claiming Space
When a MASC node, on behalf of a MASC domain, needs more address
space, it decides locally the size and the value of the address
prefix(es) it will claim from one of its parents. For example, the
decision might be based on the knowledge this node has about its
parent's address set, its siblings' claims and allocations, its own
address set, the claim messages from its siblings, and/or the demand
pattern of its children and the local domain. A sample algorithm is
given in Appendix A.
A MASC node which is not in a top-level domain can initiate a claim
toward a parent MASC domain if and only if it currently has an
established connection with at least one node in that parent domain.
After the prefix address and size are decided, the claim proceeds as
follows:
a) The claim is scheduled to be sent after a random delay in the
interval (0, [INITIATE_CLAIM_DELAY]). If a claim originated by a
node from the same MASC domain is received, and that claim
eliminates the need for the local claim, the local claim is
canceled and no further action is taken.
b) The claim is sent to one of the parents (if the domain is not a
top-level domain), all known siblings with the same parent, and
all internal peers. A Claim-Timer is then started at
[WAITING_PERIOD], and the MASC node starts listening for colliding
claims.
c) If a colliding claim is received while the Claim-Timer is running,
that claim is compared with the locally initiated claim using the
function described in Section 5.1.1. If the local claim is the
loser, a new prefix must be chosen to claim, and the loser claim's
Claim-Timer must be canceled. The loser claim can be either
explicitly withdrawn, or can be left to expire without taking
further actions. If the winning claim was originated by a node
from the same MASC domain, no new claim will be initiated. If the
local claim is the winner, no actions need to be taken.
d) If the Claim-Timer expires, the claimed prefix becomes associated
with the claimer's domain, i.e. it is considered allocated to that
domain and the following actions can be performed:
o Advertise the prefix to its parent, and to all siblings with
the same parent, by sending a PREFIX_IN_USE claim to them.
o Inject the prefix into the G-RIB of the inter-domain routing
protocol.
o Send a PREFIX_MANAGED message to all children and internal
peers, informing them that they may issue claims within the
managed space. A sub-prefix may then be claimed for local
usage (see Section 12.2).
Each MASC node receives all claims from its siblings and children. A
received claim must be evaluated against all claims saved in the
local cache using the function described in Section 5.1.1. The
output of the function will define the further processing of that
claim (see Section 11).
5.1.1. Claim Comparison Function
Each claim message includes: o a "type", being one of: PREFIX_IN_USE, CLAIM_DENIED, CLAIM_TO_EXPAND, or NEW_CLAIM (PREFIX_MANAGED and WITHDRAW are not considered as claims that have to be compared) o timestamp when the claim was initiated o the claimed prefix and lifetime o MASC Identifier of the node that originated the claim When two claims are compared, first the type is compared based on the following precedence: PREFIX_IN_USE > CLAIM_DENIED > CLAIM_TO_EXPAND > NEW_CLAIM If the type is the same, then the timestamps are used to compare the claims. In practice, two claims will have the same type if the type is either NEW_CLAIM (ordinary collision) or PREFIX_IN_USE (signal for a clash). When the timestamps are compared, the claim with the smallest, i.e. earliest timestamp wins. If the timestamps are the same, then the claim with the smallest Origin Node Identifier wins.5.2. Renewing an Existing Claim
The procedure for extending the lifetime of prefixes already in use is the same as claiming new space (see Section 5.1), except that the claim type must be CLAIM_TO_EXPAND, while the Address and the Mask of the claim (see Section 7.3) must be the same as the already allocated prefix. If the Claim-Timer expires and there is no collision, the desired lifetime is assumed.5.3. Expanding an Existing Prefix
The procedure for extending the lifetime of prefixes already in use is the same as claiming new space (see Section 5.1), except that the claim type must be CLAIM_TO_EXPAND, while the Address and the Mask of the claim (see Section 7.3) must be set to the desired values. If the Claim-Timer expires and there is no collision, the desired larger prefix is associated with the local domain.
5.4. Releasing Allocated Space
If the lifetime of a prefix allocated to the local domain expires and the domain does not need to reuse it, all resources associated with this prefix are deleted and no further actions are taken. If the lifetime of the prefix has not expired, and if no subranges of that prefix have being allocated for local usage or by some of the children domains, the space may be released by sending a withdraw message to the parent domain, all known siblings with the same parent, and all internal peers.6. Constants
MASC uses the following constants: [PORT_NUMBER] 2587. The TCP port number used to listen for incoming MASC connections, as assigned by IANA. [WAITING_PERIOD] The amount of time (in seconds) that must pass between a NEW_CLAIM (or CLAIM_TO_EXPAND), and a PREFIX_IN_USE for the same prefix. This must be long enough to reasonably span any single inter- domain network partition. Default: 172800 seconds (i.e. 48 hours). [INITIATE_CLAIM_DELAY] The amount of time (in seconds) a MASC node must wait before initiating a new claim or a claim for space expansion. This must be a random value in the interval (0, [INITIATE_CLAIM_DELAY]). Default value for [INITIATE_CLAIM_DELAY]: 600 seconds (i.e. 10 minutes). [TLD_ID] The Parent Domain Identifier used by a Top-Level Domain (which has no parent). Must be 0. [HOLDTIME] The amount of time (in seconds) that must pass without any messages received from a remote node before considering the connection is down. Default: 240 seconds (i.e. 4 minutes).
7. Message Formats
This section describes message formats used by MASC. Messages are sent over a reliable transport protocol connection. A message is processed only after it is entirely received. The maximum message size is 4096 octets. All implementations are required to support this maximum message size.7.1. Message Header Format
Each message has a fixed-size (4-octets) header. There may or may not be a data portion following the header, depending on the message type. The layout of these fields 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Length | Type | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Length: This 2-octet unsigned integer indicates the total length of the message, including the header, in octets. Thus, e.g., it allows one to locate in the transport-level stream the start of the next message. The value of the Length field must always be at least 4 and no greater than 4096, and may be further constrained, depending on the message type. No "padding" of extra data after the message is allowed, so the Length field must have the smallest value required given the rest of the message. Type: This 1-octet unsigned integer indicates the type code of the message. The following type codes are defined: 1 - OPEN 2 - UPDATE 3 - NOTIFICATION 4 - KEEPALIVE Reserved: This 1-octet field is reserved. MUST be set to zero by the sender, and MUST be ignored by the receiver.
7.2. OPEN Message Format
After a transport protocol connection is established, the first message sent by each side is an OPEN message. If the OPEN message is acceptable, a KEEPALIVE message confirming the OPEN is sent back. Once the OPEN is confirmed, UPDATE, KEEPALIVE, and NOTIFICATION messages may be exchanged. The minimum length of the OPEN message is 20 octets (including message header). In addition to the fixed-size MASC header, the OPEN message contains the following fields: 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 |R| AddrFam |Rol| Hold Time | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sender Domain Identifier (variable length) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sender MASC Node Identifier (variable length) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Parent's Domain Identifier (variable length) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + (Optional Parameters) | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Version: This 1-octet unsigned integer indicates the protocol version number of the message. The current MASC version number is 1. R bit: This 1-bit field is reserved. MUST be set to zero by the sender, and MUST be ignored by the receiver. AddrFam: This 5-bit field is the IANA-assigned address family number of the encoded prefix [IANA]. These include (among others): Number Description ------ ----------- 1 IP (IP version 4) 2 IPv6 (IP version 6)
My Role (Rol):
This 2-bit field indicates the proposed relationship of the
sending system to the receiving system:
00 = INTERNAL_PEER (sent from one internal peer to another)
01 = CHILD (sent from a child to its parent)
10 = SIBLING (sent from one sibling to another)
11 = PARENT (sent from a parent to its child)
Hold Time:
This 2-octet unsigned integer indicates the number of seconds that
the sender proposes for the value of the Hold Timer. Upon receipt
of an OPEN message, a MASC speaker MUST calculate the value of the
Hold Timer by using the smaller of its configured Hold Time for
that peer and the Hold Time received in the OPEN message. The
Hold Time MUST be either zero or at least three seconds. An
implementation may reject connections on the basis of the Hold
Time. The calculated value indicates the maximum number of
seconds that may elapse between the receipt of successive
KEEPALIVE and/or UPDATE messages by the sender. RECOMMENDED value
is [HOLDTIME] seconds.
Sender Domain Identifier:
A globally unique identifier. Its length is determined based on
the Address Family, and should be treated as an unsigned integer
(e.g. a 4-octet integer for IPv4, or a 16-octet integer for IPv6),
but must be at least 4 octets long. It should be set to the
Autonomous System number of the sender, but the network unicast
prefix address is also acceptable.
Sender MASC Node Identifier:
This field's length and format are same as the Sender Domain
Identifier field, and indicates the MASC Node Identifier of the
sender. A given MASC speaker sets the value of its MASC Node
Identifier to a globally-unique value assigned to that MASC
speaker (e.g., an IPv4 or IPv6 address). The value of the MASC
Node Identifier is determined on startup and is the same for every
MASC session opened.
Parent's Domain Identifier:
This field's length and format are same as the Sender Domain
Identifier field, and is set to the Domain Identifier of the
sender's parent (e.g. the parent's Autonomous System number, or
network prefix address), or is set to [TLD_ID] if the sender is a
TLD. Used only when Rol is INTERNAL_PEER or SIBLING, otherwise is
ignored. This field is used to determine the common parents
between siblings, to associate each sibling-to-sibling connection
with a particular parent, and to discover TLD-related
configuration problems among internal peers. If a non-TLD node
does not know yet the Domain ID of any of its parents, it can use
its own Domain ID in the OPEN messages to its internal peers.
Optional Parameters:
This field may contain a list of optional parameters, where each
parameter is encoded as a <Parameter Length, Parameter Type,
Parameter Value> triplet. The combined length of all optional
parameters can be derived from the Length field in the message
header.
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...
| Parm. Length | Parm. Type | Parameter Value (variable)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...
Parameter Length is a one octet field that contains the length of
the Parameter Value field in octets. Parameter Type is a one
octet field that unambiguously identifies individual parameters.
Parameter Value is a variable length field that is interpreted
according to the value of the Parameter Type field. Unrecognized
optional parameters MUST be silently ignored.
This document does not define any optional parameters.
7.3. UPDATE Message Format
UPDATE messages are used to transfer Claim/Collision/PrefixManaged
information between MASC speakers. The UPDATE message always
includes the fixed-size MASC header, and one or more attributes as
described below. The minimum length of the UPDATE message is 40
octets (including the message header).
Each attribute is of the form:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Type | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
All attributes are 4-octets aligned.
Length:
The Length is the length of the entire attribute, including the
length, type, and data fields. If other attributes are nested
within the data field, the length includes the size of all such
nested attributes.
Type:
This 1-octet unsigned integer indicates the type code of the
attribute. The following type codes are defined:
0 = PREFIX_IN_USE (prefix is being used by the origin)
1 = CLAIM_DENIED (the claim is refused (probably by the
origin's parent domain))
2 = CLAIM_TO_EXPAND (origin is trying to expand the size of
an existing prefix)
3 = NEW_CLAIM (origin is trying to claim a new prefix)
4 = PREFIX_MANAGED (parent is informing child of space
available)
5 = WITHDRAW (origin is withdrawing a previous claim)
Types 128-255 are reserved for "optional" attributes. If a
required attribute is unrecognized, a NOTIFICATION with UPDATE
Error Code and Unrecognized Required Attribute subcode will be
sent. Unrecognized optional attributes are simply ignored.
Reserved:
This 1-octet field is reserved. MUST be set to zero by the
sender, and MUST be ignored by the receiver.
Types 0-3 are collectively called "CLAIMs". The message format below
describes the encoding of a CLAIM, PREFIX_MANAGED and WITHDRAW.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved1 |D| AddrFam |Rol| Reserved2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Claim Timestamp |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Claim Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Claim Holdtime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Origin Domain Identifier (variable length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Origin Node Identifier (variable length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address (variable length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Mask (variable length) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ (Optional Parameters) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Reserved1:
This 1-octet field is reserved. MUST be set to zero by the
sender, and MUST be ignored by the receiver.
D-bit:
DEPRECATED_PREFIX bit. If set, indicates that the advertised
address prefix is Deprecated, otherwise the prefix is Active (see
Section 4.3).
AddrFam:
This 5-bit field is the IANA-assigned address family number of the
encoded prefix [IANA].
Rol:
This 2-bit field indicates the relationship/role of the Origin of
the message to the node sending that message:
00 = INTERNAL (originated by the sender's domain)
01 = CHILD (originated by a child of the sender's domain)
10 = SIBLING (originated by a sibling of the sender's domain)
11 = PARENT (originated by a parent of the sender's domain)
Reserved2:
This 2-octet field is reserved. MUST be set to zero by the
sender, and MUST be ignored by the receiver.
Claim Timestamp:
The timestamp of the claim when it was originated. The timestamp
is expressed in number of seconds since midnight (0 hour), January
1, 1970, Greenwich.
Claim Lifetime:
The time in seconds between the Claim Timestamp, and the time at
which the prefix will become free.
Claim Holdtime:
The time in seconds between the Claim Timestamp, and the time at
which the claim should be deleted from the local cache. For
PREFIX_IN_USE and PREFIX_MANAGED claims it should be equal to
Claim Lifetime; for CLAIM_TO_EXPAND, NEW_CLAIM, and CLAIM_DENIED
it should be equal to [WAITING_PERIOD].
Origin Domain Identifier:
The domain identifier of the claim originator. Its length and
format definition are same as the Sender Domain Identifier (see
Section 7.2).
Origin Node Identifier:
The MASC Node ID of the claim originator. Its length and format
definition are same as the Sender MASC Node Identifier (see
Section 7.2).
Address:
The address associated with the given prefix to be encoded. The
length is determined based on the Address Family (e.g. 4 octets
for IPv4, 16 for IPv6)
Mask:
The mask associated with the given prefix. The length is the same
as the Address field and is determined based on the Address
Family. The field contains the full bitmask.
Optional Parameters:
This field may contain a list of optional parameters, where each
parameter is encoded using same format as the optional parameters
of an OPEN message (see Section 7.2). Unrecognized optional
parameters MUST be silently ignored. This document does not
define any optional parameters.
7.4. KEEPALIVE Message Format
MASC does not use any transport protocol-based keep-alive mechanism to determine if peers are reachable. Instead, KEEPALIVE messages are exchanged between peers often enough as not to cause the Hold Timer to expire. A reasonable maximum time between the last KEEPALIVE or UPDATE message sent, and the time at which a KEEPALIVE message is sent, would be one third of the Hold Time interval. KEEPALIVE messages MUST NOT be sent more frequently than one per second. An implementation MAY adjust the rate at which it sends KEEPALIVE messages as a function of the Hold Time interval. If the negotiated Hold Time interval is zero, then periodic KEEPALIVE messages MUST NOT be sent. A KEEPALIVE message consists of only a message header, and has a length of 4 octets.7.5. NOTIFICATION Message Format
A NOTIFICATION message is sent when an error condition is detected. Depending on the error condition, the MASC connection might or must be closed immediately after sending the message. If the sender of the NOTIFICATION decides that the connection is to be closed, it will indicate this by zeroing the O-bit in the NOTIFICATION message (see below). In addition to the fixed-size MASC header, the NOTIFICATION message contains the following fields: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |O| Error code | Error subcode | Data | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ O-bit: Open-bit. If zero, it indicates that the sender will close the connection. If '1', it indicates that the sender has chosen to keep the connection open. Error Code: This 7-bit unsigned integer indicates the type of NOTIFICATION. The following Error Codes have been defined:
Error Code Symbolic Name Reference
1 Message Header Error Section 8.1
2 OPEN Message Error Section 8.2
3 UPDATE Message Error Section 8.3
4 Hold Timer Expired Section 8.4
5 Finite State Machine Error Section 8.5
6 NOTIFICATION Message Error Section 8.6
7 Cease Section 8.7
Error subcode:
This 1-octet unsigned integer provides more specific information
about the nature of the reported error. Each Error Code may have
one or more Error Subcodes associated with it. If no appropriate
Error Subcode is defined, then a zero (Unspecific) value is used
for the Error Subcode field, and the O-bit must be zero (i.e. the
connection will be closed). The notation used in the error
description below is: MC = Must Close connection = O-bit is zero;
CC = Can Close connection = O-bit might be zero.
Message Header Error subcodes:
0 - Unspecific (MC)
1 - Bad Message Length (MC)
2 - Bad Message Type (CC)
OPEN Message Error subcodes:
0 - Unspecific (MC)
1 - Unsupported Version Number (MC)
2 - Bad Peer Domain ID (MC)
3 - Bad Peer MASC Node ID (MC)
6 - Unacceptable Hold Time (MC)
7 - Invalid Parent Configuration (MC)
8 - Inconsistent Role (MC)
9 - Bad Parent Domain ID (MC)
10 - No Common Parent (MC)
13 - Unrecognized Address Family (MC)
UPDATE Message Error subcodes:
0 - Unspecific (MC)
1 - Malformed Attribute List (MC)
2 - Unrecognized Required Attribute (CC)
5 - Attribute Length Error (MC)
10 - Invalid Address field (CC)
11 - Invalid Mask field (CC)
12 - Non-Contiguous Mask (CC)
13 - Unrecognized Address Family (MC)
14 - Claim Type Error (CC)
15 - Origin Domain ID Error (CC)
16 - Origin Node ID Error (CC)
17 - Claim Lifetime Too Short (CC)
18 - Claim Lifetime Too Long (CC)
19 - Claim Timestamp Too Old (CC)
20 - Claim Timestamp Too New (CC)
21 - Claim Prefix Size Too Small (CC)
22 - Claim Prefix Size Too Large (CC)
23 - Illegal Origin Role Error (CC)
24 - No Appropriate Parent Prefix (CC)
25 - No Appropriate Child Prefix (CC)
26 - No Appropriate Internal Prefix (CC)
27 - No Appropriate Sibling Prefix (CC)
28 - Claim Holdtime Too Short (CC)
29 - Claim Holdtime Too Long (CC)
Hold Timer Expired subcodes (the O-bit is always zero):
0 - Unspecific (MC)
Finite State Machine Error subcodes:
0 - Unspecific (MC)
1 - Open/Close MASC Connection FSM Error (MC)
2 - Unexpected Message Type FSM Error (MC)
Cease subcodes (the O-bit is always zero):
0 - Unspecific (MC)
NOTIFICATION subcodes (the O-bit is always zero):
0 - Unspecific (MC)
Data:
This variable-length field is used to diagnose the reason for the
NOTIFICATION. The contents of the Data field depend upon the
Error Code and Error Subcode. See Section 8 for more details.
Note that the length of the Data field can be determined from the
message Length field by the formula:
Message Length = 6 + Data Length
The minimum length of the NOTIFICATION message is 6 octets
(including message header).
(page 24 continued on part 2)