draft-ietf-mboned-mzap-03.txt   draft-ietf-mboned-mzap-04.txt 
MBoneD Working Group Mark Handley MBoneD Working Group Mark Handley
Internet Engineering Task Force ISI Internet Engineering Task Force AT&T
INTERNET-DRAFT Dave Thaler INTERNET-DRAFT Dave Thaler
17 February 1999 Microsoft 22 June 1999 Microsoft
Expires August 1999 Roger Kermode Expires December 1999 Roger Kermode
Motorola Motorola
Multicast-Scope Zone Announcement Protocol (MZAP) Multicast-Scope Zone Announcement Protocol (MZAP)
<draft-ietf-mboned-mzap-03.txt> <draft-ietf-mboned-mzap-04.txt>
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with all This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC2026. provisions of Section 10 of RFC2026.
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Abstract
This document defines a protocol, the Multicast-Scope Zone Announcement This document defines a protocol, the Multicast-Scope Zone Announcement
Protocol (MZAP), for discovering the multicast administrative scope Protocol (MZAP), for discovering the multicast administrative scope
zones that are relevant at a particular location. MZAP also provides zones that are relevant at a particular location. MZAP also provides
mechanisms whereby two common misconfigurations of administrative scope mechanisms whereby common misconfigurations of administrative scope
zones can be discovered. zones can be discovered.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (1999). All Rights Reserved. Copyright (C) The Internet Society (1999). All Rights Reserved.
Draft MZAP February 1998 Draft MZAP June 1999
1. Introduction 1. Introduction
IP Multicast groups can be of global scope, or they can be restricted in The use of administratively-scoped IP multicast, as defined in RFC 2365
scope using a scoping mechanism. In this document, we only consider [1], allows packets to be addressed to a specific range of multicast
administrative scoping, as defined in RFC 2365 [1]. An administrative addresses (e.g., 239.0.0.0 to 239.255.255.255 for IPv4) such that the
scope zone is defined by a set of routers surrounding a region of the packets will not cross configured administrative boundaries, and also
network. These "border routers" are configured to not pass multicast allows such addresses to be locally assigned and hence are not required
traffic destined for a particular range of multicast addresses to or to be unique across administrative boundaries. This property of logical
from links leaving the scope zone. naming both allows for address reuse, as well as provides the capability
for infrastructure services such as address allocation, session
advertisement, and service location to use well-known addresses which
are guaranteed to have local significance within every organization.
The range of administratively-scoped addresses can be subdivided by
administrators so that multiple levels of administrative boundaries can
be simultaneously supported. As a result, a "multicast scope" is
defined as a particular range of addresses which has been given some
topological meaning.
To support such usage, a router at an administrative boundary is
configured with one or more per-interface filters, or "multicast scope
boundaries". Having such a boundary on an interface means that it will
not forward packets matching a configured range of multicast addresses
in either direction on the interface.
A specific area of the network topology which is within a boundary for a
given scope is known as a "multicast scope zone". Since the same ranges
can be reused within disjoint areas of the network, there may be many
"multicast scope zones" for any given multicast scope. A scope zone may
have zero or more textual names (in different languages) for the scope,
for human convenience. For example, if the range 239.192/14 were
assigned to span an entire corporate network, it might be given
(internally) the name "BigCo Private Scope".
Administrative scope zones may be of any size, and a particular host may Administrative scope zones may be of any size, and a particular host may
be within many administrative scope zones of various sizes. The only be within many administrative scope zones (for different scopes, i.e.,
zones a host can assume that it is within are the global zone, and a for non-overlapping ranges of addresses) of various sizes, as long as
"Local Scope". A Local Scope is defined as being the smallest scope zones that intersect topologically do not intersect in address
administrative scope zone encompassing a host, and the border is range.
configured for addresses in the range 239.255.0.0 to 239.255.255.255
inclusive. RFC 2365 specifies:
"239.255.0.0/16 is defined to be the IPv4 Local Scope. The Local
Scope is the minimal enclosing scope, and hence is not further
divisible. Although the exact extent of a Local Scope is site
dependent, locally scoped regions must obey certain topological
constraints. In particular, a Local Scope must not span any other
scope boundary. Further, a Local Scope must be completely contained
within or equal to any larger scope. In the event that scope regions
overlap in area, the area of overlap must be in its own Local Scope.
This implies that any scope boundary is also a boundary for the Local
Scope."
as well as:
"administrative scopes that intersect topologically should not
intersect in address range."
Two problems make administrative scoping difficult to deploy and Applications and services are interested in various aspects of the
difficult to use: scopes within which they reside:
o Applications which present users with a choice of which scope in
which to operate (e.g., when creating a new session, whether it is
Draft MZAP June 1999
to be confined to a corporate intranet, or whether it should go out
over the public Internet) are interested in the textual names which
have significance to users.
o Services which use "relative" multicast addresses (as defined in
[1]) in every scope are interested in the range of addresses used
by each scope, so that they can apply a constant offset and compute
which address to use in each scope.
o Address allocators are interested in the address range, and whether
they are allowed to allocate addresses within the entire range or
not.
o Some applications and services may also be interested in the
nesting relationships among scopes. For example, knowledge of the
nesting relationships can be used to perform "expanding-scope"
searches in a similar, but better behaved, manner to the well-known
expanding ring search where the TTL of a query is steadily
increased until a replier can be found. Studies have also shown
that nested scopes can be useful in localizing multicast repair
traffic [8].
Two barriers currently make administrative scoping difficult to deploy
and use:
o Applications have no way to dynamically discover information on
scopes that are relevant to them. This makes it difficult to use
administrative scope zones, and hence reduces the incentive to deploy
them.
o Misconfiguration is easy. It is difficult to detect scope zones that o Misconfiguration is easy. It is difficult to detect scope zones that
have been configured so as to not be convex (the shortest path have been configured so as to not be convex (the shortest path
between two nodes within the zone passes outside the zone), or to between two nodes within the zone passes outside the zone), or to
leak (one or more border routers were not configured correctly), or leak (one or more boundary routers were not configured correctly), or
to intersect in both area and address range. to intersect in both area and address range.
o Applications have no way to discover the scope zones that are These two barriers are addressed by this document. In particular, this
relevant to them. This makes it difficult to use administrative document defines the Multicast Scope Zone Announcement Protocol (MZAP)
scope zones, and hence reduces the incentive to deploy them. which allows an entity to learn what scope zones it is within.
Typically servers will cache the information learned from MZAP and can
Draft MZAP February 1998 then provide this information to applications in a timely fashion upon
request using other means, e.g., via MADCAP [9]. MZAP also provides
This document defines the Multicast Scope Zone Announcement Protocol diagnostic information to the boundary routers themselves that enables
(MZAP) which will provide applications with information about the scope misconfigured scope zones to be detected.
zones they are within, and also provide diagnostic information to detect
misconfigured scope zones.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", Draft MZAP June 1999
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [2].
Constants used by this protocol are shown as [NAME-OF-CONSTANT], and 2. Terminology
summarized in section 5.
2. Overview The "Local Scope" is defined in RFC 2365 [1] and represents the smallest
administrative scope larger than link-local, and the associated address
range is defined as 239.255.0.0 to 239.255.255.255 inclusive (for IPv4,
FF03::/16 for IPv6). RFC 2365 specifies:
"239.255.0.0/16 is defined to be the IPv4 Local Scope. The Local
Scope is the minimal enclosing scope, and hence is not further
divisible. Although the exact extent of a Local Scope is site
dependent, locally scoped regions must obey certain topological
constraints. In particular, a Local Scope must not span any other
scope boundary. Further, a Local Scope must be completely contained
within or equal to any larger scope. In the event that scope regions
overlap in area, the area of overlap must be in its own Local Scope.
This implies that any scope boundary is also a boundary for the Local
Scope."
A multicast scope Zone Border Router (ZBR) is a router that is A multicast scope Zone Boundary Router (ZBR) is a router that is
configured to be a zone border on one or more of its interfaces. Any configured with a boundary for a particular multicast scope on one or
interface that is configured to be a border for any administrative scope more of its interfaces. Any interface that is configured with a boundary
zone MUST also be a border for the Local Scope zone, as defined in [1]. for any administrative scope zone MUST also have a boundary for the
Local Scope zone, as described above.
Routers SHOULD be configured so that the router itself is within the Such routers SHOULD be configured so that the router itself is within
scope zone. This is should in figure 1(a), where router A is inside the the scope zone. This is shown in Figure 1(a), where router A is inside
scope zone and has the border configuration. It is possible for the the scope zone and has the boundary configuration.
first router outside the scope zone to be configured with the border, as
illustrated in figure 1(b) where routers B and C are outside the zone
and have the border configuration, but this is NOT RECOMMENDED.
............ ................ ............ ................
. . +B+--> . *B+--> . . +B+--> . *B+-->
. . / . / . . . / . / .
. * . + . . * . + .
. <---+A*---+C+-> . <---+A+---*C+-> . <---+A*---+C+-> . <---+A+---*C+->
. + . . + . . + . . + .
. / . . / . . / . . / .
. zone X <-- . . zone X <-- . . zone X <-- . . zone X <-- .
.............. .................. .............. ..................
A,B,C - routers * - border interface + - interface A,B,C - routers * - boundary interface + - interface
(a) Correct zone border (b) Incorrect zone border
Figure 1: Administrative scope zone border placement
This rule does not apply for Local Scope borders, but applies for all
other administrative scope border routers.
Draft MZAP February 1998 (a) Correct zone boundary (b) Incorrect zone boundary
When a ZBR is configured correctly, it can deduce which side of the Figure 1: Administrative scope zone boundary placement
boundary is inside the scope zone and which side is outside it. It can
also send messages into the scope zone, which it SHOULD NOT be able to
do if the router itself is considered outside the scope zone.
Such a ZBR should then send periodic Zone Announcement Messages (ZAMs) It is possible for the first router outside the scope zone to be
for the zone for which it is configured as a border from one of its configured with the boundary, as illustrated in Figure 1(b) where
interfaces that go into that scope zone. These messages are multicast
to the address [MZAP-LOCAL-GROUP] in the Local Scope.
Each ZBR also listens for messages from other ZBRs for the same border. Draft MZAP June 1999
The ZBR with the lowest interface IP address within the zone from those
ZBRs forming the zone border becomes the zone-id router for the zone.
The combination of this IP address and the first multicast address in
the scoped range serve to uniquely identify the scope zone.
When a ZBR receives a ZAM for some scope zone: routers B and C are outside the zone and have the boundary
configuration, whereas A does not, but this is NOT RECOMMENDED. This
rule does not apply for Local Scope boundaries, but applies for all
other boundary routers.
o If the ZAM was received on an interface with a boundary for the given We next define the term "Zone ID" to mean the lowest IP address used by
scope, the ZAM is not forwarded. For example, router D in figure 2 any ZBR for a particular zone for sourcing MZAP messages into that scope
will not forward the ZAM. zone. The combination of this IP address and the first multicast
address in the scope range serve to uniquely identify the scope zone.
Each ZBR listens for messages from other ZBRs for the same boundary, and
can determine the Zone ID based on the source addresses seen. The Zone
ID may change over time as ZBRs come up and down.
o If the ZAM was received on an interface which is NOT a Local Scope The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
boundary, and the last Local Zone ID Address in the path list is 0, "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
the ZBR fills in the Local Zone ID Address of the local zone from document are to be interpreted as described in RFC 2119 [2].
which the ZAM was received.
o If a ZAM for the same scope (as identified by the origin Zone ID and Constants used by this protocol are shown as [NAME-OF-CONSTANT], and
first multicast address) was received in the last [ZAM-DUP-TIME] summarized in section 7.
seconds, the ZAM is not forwarded. For example, when router C in
figure 2 receives the ZAM via B, it will not be forwarded, since it
has just forwarded the ZAM from E.
o Otherwise, the ZAM is cached for at least [ZAM-DUP-TIME] seconds. 3. Overview
o If the Zone ID of the Local Scope zone in which the ZBR resides is When a ZBR is configured correctly, it can deduce which side of the
not already in the ZAM's path list, then the ZAM is immediately re- boundary is inside the scope zone and which side is outside it.
originated within the Local Scope zone. It adds its own address and
the zone-id of the Local Scope zone into which the message is being
forwarded to the ZAM path list before doing so. A ZBR receiving a ZAM
with a non-null path list MUST NOT forward that ZAM back into a Local
Scope zone that is contained in the path list. For example, in
figure 2, router F, which did not get the ZAM via A due to packet
loss, will not forward the ZAM from B back into Zone 2 since the path
list has { (E,1), (A,2), (B,3) } and hence Zone 2 already appears.
Draft MZAP February 1998 Such a ZBR then sends periodic Zone Announcement Messages (ZAMs) for
each zone for which it is configured as a boundary into that scope zone,
containing information on the scope zone's address range, Zone ID, and
textual names. These messages are multicast to the well-known address
[MZAP-LOCAL-GROUP] in the Local Scope, and are relayed across Local
Scope boundaries into all Local Scope zones within the scope zone
referred to by the ZAM message, as shown in Figure 2.
o In addition, the ZBR re-originates the ZAM out each interface with a Draft MZAP June 1999
Local Scope boundary (except that it is not sent back out the
interface over which it was received, nor is it sent into any local
scope zone whose ID is known and appears in the path list). In each
such ZAM re-originated, the ZBR adds its own IP address to the path
list, as well as the Zone ID Address of the Local Scope Zone into
which the ZAM is being sent, or 0 if the ID is unknown. (For example,
if the other end of a point-to-point link also has a boundary on the
interface, then the link has no Local Scope Zone ID.)
########################### ###########################
# Zone1 = Zone2 # ##### = large scope zone border # Zone1 = Zone2 # ##### = large scope zone boundary
*E-----+--->A*-----+-x # *E-----+--->A*-----+-x #
# | = v # ===== = Local Scope boundaries # | = v # ===== = Local Scope boundaries
# | ======*===*==# # | ======*===*==#
# | = B F # ----> = path of ZAM originated by E # | = B F # ----> = path of ZAM originated by E
# +--->C*-> | ^ # G*<-----+--->C*-> | ^ #
# v = <-+---+ # ABCDE = ZBRs # v = <-+---+ # ABCDE = ZBRs
# D = Zone3 # # D = Zone3 #
#######*################### * = border interface #######*################### * = boundary interface
Figure 2: ZAM Flooding Example Figure 2: ZAM Flooding Example
The packet also contains a Zones Traveled Limit. If the number of Local Any entity can thus listen on a single well-known group address and
Zone IDs in the ZAM path becomes equal to the Zones Traveled Limit, the learn about all scopes in which it resides.
packet should be dropped. Zones Traveled Limit is set when the packet is
first sent, and defaults to 32, but can be set to a lower value if a
network administrator knows the expected size of the zone.
Additional messages called Zone Convexity Messages (ZCMs) SHOULD also be
sent to the [ZCM-RELATIVE-GROUP] in the scoped range itself. As these
are not locally scoped packets, they are simply multicast across the
scope zone itself, and require no path to be built up, nor any special
processing by Local Scope zone ZBRs. These messages are used to detect
non-convex administrative scope zones, as illustrated in figure 3, where
the path between B and D goes outside the scope (through A and E). Here
Router B and Router C originates ZCMs, each reporting each other's
presence. Router D cannot see Router B's messages, but can see C's
report of B, and so can conclude the zone is not convex.
Draft MZAP February 1998
#####*####========
# B # = ##### = non-convex scope boundary
# |->A* =
# | # = ===== = other scope boundaries
# | ####*####
# | E # ----> = path of B's ZAM
# v D*
# C # * = border interface
#####*############
Figure 3: Non-convexity detection
2.1. Nesting 3.1. Scope Nesting
MZAP also provides the ability to discover the nesting relationships MZAP also provides the ability to discover the nesting relationships
between scope zones. Two zones are nested if one is comprised of a between scope zones. Two zones are nested if one is comprised of a
subset of the routers in the other, as shown in Figure 4. subset of the routers in the other, as shown in Figure 3.
+-----------+ +-----------+ +-------------+ +-----------+ +-----------+ +-------------+
| Zone 1 | | Zone 3 | | Zone 5 | | Zone 1 | | Zone 3 | | Zone 5 |
| +------+| | +------+ | .........|.. | +------+| | +------+ | .........|..
| |Zone 2|| | |Zone 4| | : Zone 6 | : | |Zone 2|| | |Zone 4| | : Zone 6 | :
| +--A---+| | C | | D | : | +--A---+| | C | | D | :
+-----------+ +----+--B---+ +--------E----+ : +-----------+ +----+--B---+ +--------E----+ :
:..........: :..........:
(a) "Contained" (b) "Common Border" (c) "Overlap" (a) "Contained" (b) "Common Border" (c) "Overlap"
Zone 2 nests Zone 4 nests Zones 5 and 6 Zone 2 nests Zone 4 nests Zones 5 and 6
inside Zone 1 inside Zone 3 do not nest inside Zone 1 inside Zone 3 do not nest
Figure 4: Zone nesting examples Figure 3: Zone nesting examples
Nested scopes provide the ability to perform "expanding-scope" searches
in a similar, but better behaved, manner to the well-known expanding
ring search where the TTL of a query is steadily increased until a
replier can be found. Studies have also shown that nested scopes can be
useful in localizing multicast repair traffic [8].
A ZBR cannot independently determine whether one zone is nested inside A ZBR cannot independently determine whether one zone is nested inside
another. However, they can determine that one zone does NOT nest inside another. However, it can determine that one zone does NOT nest inside
another. For example, in figure 4: another. For example, in figure 4:
Draft MZAP February 1998
o ZBR A will pass ZAMs for zone 1 but will prevent ZAMs from zone 2 o ZBR A will pass ZAMs for zone 1 but will prevent ZAMs from zone 2
from leaving zone 2. ZBR A can thus determine that zone 1 does not from leaving zone 2. When ZBR A first receives a ZAM for zone 1, it
nest within zone 2, but it cannot, however, determine whether zone 2
nests within zone 1. Draft MZAP June 1999
then knows that zone 1 does not nest within zone 2, but it cannot,
however, determine whether zone 2 nests within zone 1.
o ZBR B acts as ZBR for both zones 3 and 4, and hence cannot determine o ZBR B acts as ZBR for both zones 3 and 4, and hence cannot determine
if one is nested inside the other. However, ZBR C can determine that if one is nested inside the other. However, ZBR C can determine that
zone 3 does not nest inside zone 4 since it is a ZBR for zone 4 and zone 3 does not nest inside zone 4 when it receives a ZAM for zone 3,
not zone 3. since it is a ZBR for zone 4 but not zone 3.
o ZBR D only acts as ZBR zone 6 and not 5, hence ZBR D can deduce that o ZBR D only acts as ZBR zone 6 and not 5, hence ZBR D can deduce that
zone 6 does not nest inside zone 5. Similarly, ZBR E only acts as zone 5 does not nest inside zone 6 upon hearing a ZAM for zone 5.
ZBR zone 5 and not 6, hence ZBR E can deduce that zone 5 does not Similarly, ZBR E only acts as ZBR zone 5 and not 6, hence ZBR E can
nest inside zone 6. deduce that zone 6 does not nest inside zone 5 upon hearing a ZAM for
zone 6.
The fact that ZBRs can determine that one zone does not nest inside The fact that ZBRs can determine that one zone does not nest inside
another, but not that a zone does nest inside another, means that another, but not that a zone does nest inside another, means that
nesting must be determined in a distributed fashion. nesting must be determined in a distributed fashion. This is done by
sending Not-Inside Messages (NIMs) which express the fact that a zone X
When a ZBR receives a ZAM for a scope X for which it is NOT a border, it is not inside a zone Y. Such messages are sent to the well-known
creates a local "X not inside" state entry, if such an entry does not [MZAP-LOCAL-GROUP] and are thus seen by the same entities listening to
already exist. It then restarts the entry's timer at [ZAM-HOLDTIME]. ZAM messages (e.g., MADCAP servers). Such entities can then determine
Existence of this state indicates that the ZBR knows that X does not the nesting relationship between two scopes based on a sustained absence
nest inside any scope for which it is a border. If the entry's timer of any evidence to the contrary.
expires (because no more ZAMs for X are heard for [ZAM-HOLDTIME]), the
entry is deleted.
Periodically, at an interval of [NIM-INTERVAL], a router originates a
Not-Inside Message (NIM) for each "X not inside" entry, for each scope
zone Y for which it is a border. Like a ZAM, this message is multicast
to the address [MZAP-LOCAL-GROUP] from one of its interfaces in Y.
When a ZBR receives a NIM saying that "X is not inside Y", it is 3.2. Other Messages
forwarded, unmodified, in a manner similar to ZAMs:
o If the NIM was received on an interface with a boundary for either X Two other message types, Zone Convexity Messages (ZCMs) and Zone Limit
or Y, the NIM is discarded. Exceeded (ZLE) messages, are used only by routers, and enable them to
compare their configurations for consistency and detect
misconfigurations. These messages are sent to MZAP's relative address
within the scope range associated with the scope zone to which they
refer, and hence are typically not seen by entities other than routers.
Their use in detecting specific misconfiguration scenarios will be
covered in the next section.
o Unlike ZAMs, if the NIM was not received on the interface towards the Packet formats for all messages are described in Section 5.
message origin (according to the Multicast RIB), the NIM is
discarded.
o If a NIM for the same X and Y (where each is identified by its first 3.3. Zone IDs
multicast address) was received in the last [ZAM-DUP-TIME] seconds,
the NIM is not forwarded.
Draft MZAP February 1998 When a boundary router first starts up, it uses its lowest IP address
which it considers to be inside a given zone, and which is routable
everywhere within the zone (for example, not a link-local address), as
the Zone ID for that zone. It then schedules ZCM and ZAM messages to be
o Otherwise, the NIM is cached for at least [ZAM-DUP-TIME] seconds. Draft MZAP June 1999
o The ZBR then re-originates the NIM (unchanged) into each local scope sent in the future (it does not send them immediately). When a ZAM or
zone in which it has interfaces, except that it is not sent back into ZCM is received for the given scope, the sender is added to the local
the local scope zone from which the message was received, nor is it list of ZBRs (including itself) for that scope, and the Zone ID is
sent out any interface with a boundary for either X or Y. updated to be the lowest IP address in the list. Entries in the list
are eventually timed out if no further messages are received from that
ZBR, such that the Zone ID will converge to the lowest address of any
active ZBR for the scope.
3. Usage 4. Detecting Router Misconfigurations
In this section, we summarize how to inform internal entities of scopes In this section, we cover how to detect various error conditions. If any
in which they reside, as well as how to detect various error conditions. error is detected, the router should attempt to alert a network
If any error is detected, the router should attempt to alert a network
administrator to the nature of the misconfiguration. The means to do administrator to the nature of the misconfiguration. The means to do
this lies outside the scope of MZAP. this lies outside the scope of MZAP.
3.1. Zone IDs 4.1. Detecting non-convex scope zones
When a border router first starts up, it uses its lowest IP address
which it considers to be inside a given zone as the Zone ID for that
zone, and schedules the ZCM and ZAM messages to be sent in the future
(it does not send them immediately). When a ZAM or ZCM is received for
the given scope, the sender is added to the local list of ZBRs
(including itself) for that scope, and the Zone ID is updated to be the
lowest IP address in the list. Entries in the list are eventually timed
out if no further messages are received from that ZBR, such that the
Zone ID will converge to the lowest address of any active ZBR for the
scope.
3.2. Informing internal entities of scopes
Any host or application may join the [MZAP-LOCAL-GROUP] to listen for
Zone Announcement Messages to build up a list of the scope zones that
are relevant locally, and for Not-Inside Messages if it wishes to learn
nesting information. However, listening for to such messages is not the
recommended method for regular applications to discover this
information. These applications will normally query a local Multicast
Address Allocation Server [3], which in turn listens to Zone
Announcement Messages and Not-Inside Messages to maintain scope
information.
Draft MZAP February 1998 Zone Convexity Messages (ZCMs) are used by routers to detect non-convex
administrative scope zones, which are one possible misconfiguration.
Non-convex scope zones can cause problems for applications since a
receiver may never see administratively-scoped packets from a sender
within the same scope zone, since packets travelling between them may be
dropped at the boundary.
An internal entity may assume that X nests within Y if: In the example illustrated in Figure 4, the path between B and D goes
outside the scope (through A and E). Here, Router B and Router C send
ZCMs within a given scope zone for which they each have a boundary, with
each reporting the other boundary routers of the zone from which they
have heard. In Figure 4, Router D cannot see Router B's messages, but
can see C's report of B, and so can conclude the zone is not convex.
a) it first heard ZAMs for both X and Y at least [NIM-HOLDTIME] #####*####========
seconds ago, AND # B # = ##### = non-convex scope boundary
# |->A* =
# | # = ===== = other scope boundaries
# | ####*####
# | E # ----> = path of B's ZCM
# v D*
# C # * = boundary interface
#####*############
b) it has not heard a NIM indicating that "X not inside Y" for at Figure 4: Non-convexity detection
least [NIM-HOLDTIME] seconds.
3.3. Detecting non-convex scope zones Draft MZAP June 1999
Non-convex scope zones can be detected via two methods: Non-convex scope zones can be detected via two methods:
(1) If a ZBR is listed in ZCMs received, but the next-hop interface (1) If a ZBR is listed in ZCMs received, but the next-hop interface
(according to the multicast RIB) towards that ZBR is outside the (according to the multicast RIB) towards that ZBR is outside the
scope zone, or scope zone, or
(2) If a ZBR is listed in ZCMs received, but no ZCM is received from (2) If a ZBR is listed in ZCMs received, but no ZCM is received from
that ZBR for [ZCM-HOLDTIME] seconds, as illustrated in figure 3. that ZBR for [ZCM-HOLDTIME] seconds, as illustrated in Figure 3.
Zone Convexity Messages MAY also be sent and received by correctly Zone Convexity Messages MAY also be sent and received by correctly
configured ordinary hosts within a scope region, which may be a useful configured ordinary hosts within a scope region, which may be a useful
diagnostic facility that does not require privileged access. diagnostic facility that does not require privileged access.
3.4. Detecting leaky boundaries for non-local scopes 4.2. Detecting leaky boundaries for non-local scopes
A "leaky" boundary is one which logically has a "hole" due to some
router not having a boundary applied on an interface where one ought to
exist. Hence, the boundary does not completely surround a piece of the
network, resulting in scoped data leaking outside.
Leaky scope boundaries can be detected via two methods: Leaky scope boundaries can be detected via two methods:
(1) If it receives ZAMs originating inside the scope boundary on an (1) If it receives ZAMs originating inside the scope boundary on an
interface that points outside the zone boundary. Such a ZAM interface that points outside the zone boundary. Such a ZAM
message must have escaped the zone through a leak, and flooded back message must have escaped the zone through a leak, and flooded back
around behind the boundary. This is illustrated in Figure 5. around behind the boundary. This is illustrated in Figure 5.
=============#####*######## =============#####*########
= Zone1 # A Zone2 # C = misconfigured router = Zone1 # A Zone2 # C = misconfigured router
= +---->*E v # = +---->*E v #
= | # B # ##### = leaky scope boundary = | # B # ##### = leaky scope boundary
=======*=====#====*=======# =======*=====#====*=======#
= D # | # ===== = other scope boundaries = D # | # ===== = other scope boundaries
= ^-----*C<--+ # = ^-----*C<--+ #
= Zone4 # Zone3 # ----> = path of ZAMs = Zone4 # Zone3 # ----> = path of ZAMs
=============############## =============##############
Figure 5: ZAM Leaking Figure 5: ZAM Leaking
Draft MZAP February 1998 (2) If a Zone Length Exceeded (ZLE) message is received. The ZAM
packet also contains a Zones Traveled Limit. If the number of
Local Scope zones traversed becomes equal to the Zones Traveled
Limit, a ZLE message is generated (the suppression mechanism for
preventing implosion is described later in the Processing Rules
(2) If a ZLE message is received. Draft MZAP June 1999
section). ZLEs detect leaks where packets do not return to another
part of the same scope zone, but instead reach other Local Scope
zones far away from the ZAM originator.
In either case, the misconfigured router will be either the message In either case, the misconfigured router will be either the message
origin, or one of the routers in the path list included in the message origin, or one of the routers in the ZBR path list which is included in
received. the message received (or perhaps a router on the path between two such
ZBRs which ought to have been a ZBR itself).
3.5. Detecting a leaky Local Scope zone 4.3. Detecting a leaky Local Scope zone
A local scope is leaky if a router has an administrative scope boundary A local scope is leaky if a router has an administrative scope boundary
on some interface, but does not have a Local Scope boundary on that on some interface, but does not have a Local Scope boundary on that
interface as specified in RFC 2365. This can be detected via the interface as specified in RFC 2365. This can be detected via the
following method: following method:
o If a ZAM for a given scope is received by a ZBR which is a border for o If a ZAM for a given scope is received by a ZBR which is a boundary
that scope, it compares the Origin's Scope Zone ID in the ZAM with for that scope, it compares the Origin's Scope Zone ID in the ZAM
its own Zone ID for the given scope. If the two do not match, this with its own Zone ID for the given scope. If the two do not match,
is evidence of a misconfiguration. Since a temporary mismatch may this is evidence of a misconfiguration. Since a temporary mismatch
result immediately after a recent change in the reachability of the may result immediately after a recent change in the reachability of
lowest-addressed ZBR, misconfiguration should be assumed only if the the lowest-addressed ZBR, misconfiguration should be assumed only if
mismatch is persistent. the mismatch is persistent.
The exact location of the problem can be found by doing an mtrace [5] The exact location of the problem can be found by doing an mtrace [5]
from the router detecting the problem, back to the ZAM origin, for any from the router detecting the problem, back to the ZAM origin, for any
group within the address range identified by the ZAM. The router at group within the address range identified by the ZAM. The router at
fault will be the one reporting that a boundary was reached. fault will be the one reporting that a boundary was reached.
3.6. Detecting conflicting scope zones 4.4. Detecting conflicting scope zones
Conflicting address ranges can be detected via the following method: Conflicting address ranges can be detected via the following method:
o If a ZBR receives a ZAM for a given scope, and the included start and o If a ZBR receives a ZAM for a given scope, and the included start and
end addresses overlap with, but are not identical to, the start and end addresses overlap with, but are not identical to, the start and
end addresses of a locally-configured scope. end addresses of a locally-configured scope.
Conflicting scope names can be detected via the following method: Conflicting scope names can be detected via the following method:
o If a ZBR is configured with a non-empty scope name for a given scope, o If a ZBR is configured with a textual name for a given scope and
and it receives a ZAM with a non-empty scope name for the same scope, language, and it receives a ZAM or ZCM with a name for the same scope
and the scope names do not match. and language, but the scope names do not match.
Draft MZAP June 1999
Detecting either type of conflict above indicates that either the local Detecting either type of conflict above indicates that either the local
router or router originating the message is misconfigured. router or the router originating the message is misconfigured.
Configuration tools SHOULD strip white space from the beginning and end Configuration tools SHOULD strip white space from the beginning and end
Draft MZAP February 1998
of each name to avoid accidental misconfiguration. of each name to avoid accidental misconfiguration.
3.7. Packet Formats 5. Packet Formats
All MZAP messages are sent over UDP, with a destination port of [MZAP- All MZAP messages are sent over UDP, with a destination port of [MZAP-
PORT]. The common MZAP message header (which follows the UDP header), PORT] and an IPv4 TTL or IPv6 Hop Limit of 255.
is shown below:
When sending an MZAP message referring to a given scope zone, a ZBR MUST
use a source address which will have significance everywhere within the
scope zone to which the message refers. For example, link-local
addresses MUST NOT be used.
The common MZAP message header (which follows the UDP header), is shown
below:
0 1 2 3 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 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 |B| PTYPE |Address Family | NameCount | | Version |B| PTYPE |Address Family | NameCount |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message Origin | | Message Origin |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Zone ID Address | | Zone ID Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Zone Start Address | | Zone Start Address |
skipping to change at page 11, line 41 skipping to change at page 12, line 4
| . . . | Encoded Zone Name-N (variable length) | | . . . | Encoded Zone Name-N (variable length) |
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Padding (if needed) | | | Padding (if needed) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Version: Version:
The version defined in this document is version 0. The version defined in this document is version 0.
"Big" scope bit (B): "Big" scope bit (B):
If clear, indicates that the addresses in the scoped range are not If clear, indicates that the addresses in the scoped range are not
Draft MZAP June 1999
subdividable, and that address allocators may utilize the entire subdividable, and that address allocators may utilize the entire
range. If set, address allocators should not use the entire range, range. If set, address allocators should not use the entire range,
but should learn an appropriate sub-range via another mechanism but should learn an appropriate sub-range via another mechanism
(e.g., AAP [7]). (e.g., AAP [7]).
Draft MZAP February 1998
Packet Type (PTYPE): Packet Type (PTYPE):
The packet types defined in this document are: The packet types defined in this document are:
0: Zone Announcement Message (ZAM) 0: Zone Announcement Message (ZAM)
1: Zone Limit Exceeded (ZLE) 1: Zone Limit Exceeded (ZLE)
2: Zone Convexity Message (ZCM) 2: Zone Convexity Message (ZCM)
3: Not-Inside Message (NIM) 3: Not-Inside Message (NIM)
Address Family: Address Family:
The IANA-assigned address family number identifying the address The IANA-assigned address family number [10,11] identifying the
family for all addresses in the packet. The families defined for IP address family for all addresses in the packet. The families defined
are: for IP are:
1: IPv4 1: IPv4
2: IPv6 2: IPv6
Name Count: Name Count:
The number of encoded zone name blocks in this packet. The count may The number of encoded zone name blocks in this packet. The count may
be zero. be zero.
Zone Start Address: 32 bits (IPv4) or 128 bits (IPv6) Zone Start Address: 32 bits (IPv4) or 128 bits (IPv6)
This gives the start address for the scope zone border. For example, This gives the start address for the scope zone boundary. For
if the zone is a border for 239.1.0.0 to 239.1.0.255, then Zone Start example, if the zone is a boundary for 239.1.0.0 to 239.1.0.255, then
Address is 239.1.0.0. Zone Start Address is 239.1.0.0.
Zone End Address: 32 bits (IPv4) or 128 bits (IPv6) Zone End Address: 32 bits (IPv4) or 128 bits (IPv6)
This gives the ending address for the scope zone border. For This gives the ending address for the scope zone boundary. For
example, if the zone is a border for 239.1.0.0 to 239.1.0.255, then example, if the zone is a boundary for 239.1.0.0 to 239.1.0.255, then
Zone End Address is 239.1.0.255. Zone End Address is 239.1.0.255.
Message Origin: 32 bits (IPv4) or 128 bits (IPv6) Message Origin: 32 bits (IPv4) or 128 bits (IPv6)
This gives the IP address of the interface that originated the This gives the IP address of the interface that originated the
message. message.
Zone ID Address: 32 bits (IPv4) or 128 bits (IPv6) Zone ID Address: 32 bits (IPv4) or 128 bits (IPv6)
This gives the lowest IP address of a boundary router that has been This gives the lowest IP address of a boundary router that has been
observed in the zone originating the message. Together with Zone observed in the zone originating the message. Together with Zone
Start Address and Zone End Address, it forms a unique ID for the Start Address and Zone End Address, it forms a unique ID for the
zone. Note that this ID is NOT the ID of the Local Scope zone in zone. Note that this ID is usually different from the ID of the
which the origin resides. Local Scope zone in which the origin resides.
Draft MZAP February 1998
Encoded Zone Name: Encoded Zone Name:
Draft MZAP June 1999
+--------------------+ +--------------------+
|D| Reserved (7 bits)| |D| Reserved (7 bits)|
+--------------------+ +--------------------+
| LangLen (1 byte) | | LangLen (1 byte) |
+--------------------+-----------+ +--------------------+-----------+
| Language Tag (variable size) | | Language Tag (variable size) |
+--------------------+-----------+ +--------------------+-----------+
| NameLen (1 byte) | | NameLen (1 byte) |
+--------------------+-----------+ +--------------------+-----------+
| Zone Name (variable size) | | Zone Name (variable size) |
skipping to change at page 13, line 43 skipping to change at page 13, line 42
Name Len: Name Len:
The length, in bytes, of the Zone Name field. The length MUST NOT be The length, in bytes, of the Zone Name field. The length MUST NOT be
zero. zero.
Zone Name: multiple of 8 bits Zone Name: multiple of 8 bits
The Zone Name is an ISO 10646 character string in UTF-8 encoding [4] The Zone Name is an ISO 10646 character string in UTF-8 encoding [4]
indicating the name given to the scope zone (eg: ``ISI-West Site''). indicating the name given to the scope zone (eg: ``ISI-West Site'').
It should be relatively short and MUST be less than 256 bytes in It should be relatively short and MUST be less than 256 bytes in
length. White space SHOULD be stripped from the beginning and end of length. White space SHOULD be stripped from the beginning and end of
each name before encoding, to avoid accidental conflicts. All the each name before encoding, to avoid accidental conflicts.
border routers to the same region SHOULD be configured to give the
same Zone Name, or a zero length string MAY be given. A zero length
string is taken to mean that another router is expected to be
configured with the zone name. Having ALL the ZBRs for a scope zone
announce zero length names should be considered an error.
Padding (if needed): Padding (if needed):
The end of the MZAP header is padded with null bytes until it is 4- The end of the MZAP header is padded with null bytes until it is 4-
Draft MZAP February 1998
byte aligned. byte aligned.
Draft MZAP February 1998 Draft MZAP June 1999
3.7.1. Zone Announcement Message 5.1. Zone Announcement Message
A Zone Announcement Message has PTYPE=0, and is periodically sent by a A Zone Announcement Message has PTYPE=0, and is periodically sent by a
ZBR for each scope for which it is a border, EXCEPT: ZBR for each scope for which it is a boundary, EXCEPT:
o the Global Scope
o the Local Scope o the Local Scope
o the Link-local scope o the Link-local scope
The format of a Zone Announcement Message is shown below: The format of a Zone Announcement Message is shown below:
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
MZAP Header MZAP Header
skipping to change at page 15, line 38 skipping to change at page 14, line 36
| Router Address 1 | | Router Address 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Zone ID Address 1 | | Local Zone ID Address 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
..... .....
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Router Address N | | Router Address N |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Zone ID Address N | | Local Zone ID Address N |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Authentication Block (optional)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields are defined as follows: The fields are defined as follows:
Zones Traveled (ZT): 8 bits Zones Traveled (ZT): 8 bits
This gives the number of Local Zone IDs contained in this message This gives the number of Local Zone IDs contained in this message
path. path.
Zones Traveled Limit (ZTL): 8 bits Zones Traveled Limit (ZTL): 8 bits
This gives the limit on number of local zones that the packet can This gives the limit on number of local zones that the packet can
traverse before it MUST be dropped. A value of 0 indicates that no traverse before it MUST be dropped. A value of 0 indicates that no
limit exists. limit exists.
Draft MZAP February 1998
Hold Time: Hold Time:
The time, in seconds, after which the receiver may assume the scope The time, in seconds, after which the receiver may assume the scope
no longer exists, if no subsequent ZAM is received. This should be no longer exists, if no subsequent ZAM is received. This should be
set to [ZAM-HOLDTIME]. set to [ZAM-HOLDTIME].
Draft MZAP June 1999
Zone Path: multiple of 64 bits (IPv4) or 256 bits (IPv6) Zone Path: multiple of 64 bits (IPv4) or 256 bits (IPv6)
The zone path is a list of Local Zone ID Addresses (the Zone ID The zone path is a list of Local Zone ID Addresses (the Zone ID
Address of a local zone) through which the ZAM has passed, and IP Address of a local zone) through which the ZAM has passed, and IP
addresses of the router that forwarded the packet. The origin router addresses of the router that forwarded the packet. The origin router
fills in the "Local Zone ID Address 0" field when sending the ZAM. fills in the "Local Zone ID Address 0" field when sending the ZAM.
Every Local Scope router that forwards the ZAM across a Local Scope Every Local Scope router that forwards the ZAM across a Local Scope
boundary MUST add the Local Zone ID Address of the local zone that boundary MUST add the Local Zone ID Address of the local zone that
the packet of the zone into which the message is being forwarded, and the packet of the zone into which the message is being forwarded, and
its own IP address to the end of this list, and increment ZT its own IP address to the end of this list, and increment ZT
accordingly. The zone path is empty which the ZAM is first sent. accordingly. The zone path is empty which the ZAM is first sent.
Authentication Block: 5.2. Zone Limit Exceeded (ZLE)
If present, this provides information which can be used to
authenticate the sender of the ZAM (i.e. Router Address N, if ZT is
non-zero, or Message Origin, if ZT is zero). (TBD: any reason not to
re-use SAP's "Authentication Header" here?)
3.7.2. Zone Limit Exceeded (ZLE)
This packet is sent by a local-zone border router that would have
exceeded the Zone Traveled Limit if it had forwarded a ZAM packet. To
avoid ZLE implosion, ZLEs are multicast with a random delay and
suppressed by other ZLEs. It is only scheduled if at least [ZLE-MIN-
INTERVAL] seconds have elapsed since it previously sent a ZLE to any
destination. To schedule a ZLE, the router sets a random delay timer
within the interval [ZLE-SUPPRESSION-INTERVAL], and listens to the
[MZAP-RELATIVE-GROUP] within the included scope for other ZLEs. If any
are received before the random delay timer expires, the timer is cleared
and the ZLE is not sent. If the timer expires, the router sends a ZLE
to the [MZAP-RELATIVE-GROUP] within the indicated scope.
The method used to choose a random delay (T) is as follows:
Choose a random value X from the uniform random interval [0:1]
Let C = 256
Set T = [ZLE-SUPPRESSION-INTERVAL] log( C*X + 1) / log(C)
This method ensures that close to one ZBR will respond.
The format of a ZLE is shown below: The format of a ZLE is shown below:
Draft MZAP February 1998
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
MZAP Header MZAP Header
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ZT | ZTL | unused | | ZT | ZTL | Hold Time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Zone ID Address 0 | | Local Zone ID Address 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Router Address 1 | | Router Address 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Zone ID Address 1 | | Local Zone ID Address 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
..... .....
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Router Address N | | Router Address N |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Zone ID Address N | | Local Zone ID Address N |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
All fields are copied from the ZAM, except PTYPE which is set to one. All fields are copied from the ZAM, except PTYPE which is set to one.
A router receiving ZLE messages SHOULD log them and attempt to alert the 5.3. Zone Convexity Message
network administrator that the scope zone is misconfigured.
3.7.3. Zone Convexity Message
A Zone Announcement Message has PTYPE=2, and is periodically sent by a A Zone Announcement Message has PTYPE=2, and is periodically sent by a
ZBR for each scope for which it is a border, EXCEPT: ZBR for each scope for which it is a boundary (except the Link-local
scope). Note that ZCM's ARE sent in the Local Scope.
o the Global Scope
o the Link-local scope Draft MZAP June 1999
(Note that ZCM's ARE sent in the Local Scope.)
Unlike Zone Announcement Messages which are sent to the [MZAP-LOCAL- Unlike Zone Announcement Messages which are sent to the [MZAP-LOCAL-
GROUP], Zone Convexity Messages are sent to the [ZCM-RELATIVE-GROUP] in GROUP], Zone Convexity Messages are sent to the [ZCM-RELATIVE-GROUP] in
the scope zone itself. The format of a ZCM is shown below: the scope zone itself. The format of a ZCM is shown below:
Draft MZAP February 1998
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
MZAP Header MZAP Header
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ZNUM | unused | Hold Time | | ZNUM | unused | Hold Time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ZBR Address 1 | | ZBR Address 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
..... .....
skipping to change at page 18, line 38 skipping to change at page 16, line 41
is no longer reachable, if no subsequent ZCM is received. This is no longer reachable, if no subsequent ZCM is received. This
should be set to [ZCM-HOLDTIME]. should be set to [ZCM-HOLDTIME].
ZBR Address: 32 bits (IPv4) or 128 bits (IPv6) ZBR Address: 32 bits (IPv4) or 128 bits (IPv6)
These fields give the addresses of the other ZBRs from which the These fields give the addresses of the other ZBRs from which the
Message Origin ZBR has received ZCMs but whose hold time has not Message Origin ZBR has received ZCMs but whose hold time has not
expired. The router should include all such addresses which fit in expired. The router should include all such addresses which fit in
the packet, preferring those which it has not included recently if the packet, preferring those which it has not included recently if
all do not fit. all do not fit.
3.7.4. Not-Inside Message 5.4. Not-Inside Message
A Not-Inside Message (NIM) has PTYPE=3, and is periodically sent by a A Not-Inside Message (NIM) has PTYPE=3, and is periodically sent by a
ZBR which knows that a scope X does not nest within another scope Y ("X ZBR which knows that a scope X does not nest within another scope Y ("X
not inside Y"): not inside Y"):
The format of a Not Inside Message is shown below: The format of a Not-Inside Message is shown below:
Draft MZAP February 1998 Draft MZAP June 1999
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
MZAP Header MZAP Header
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Not-Inside Zone Start Address | | Not-Inside Zone Start Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Authentication Block (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields are as follows: The fields are as follows:
MZAP Header: MZAP Header:
Header fields identifying the scope X. The Name Count may be 0. Header fields identifying the scope X. The Name Count may be 0.
Not-Inside Zone Start Address: 32 bits (IPv4) or 128 bits (IPv6) Not-Inside Zone Start Address: 32 bits (IPv4) or 128 bits (IPv6)
This gives the start address for the scope Y. This gives the start address for the scope Y.
Authentication Block: 6. Message Processing Rules
If present, this provides information which can be used to
authenticate the sender of the NIM (i.e. Message Origin in the MZAP
Header).
4. Message Timing 6.1. Internal entities listening to MZAP messages
Any host or application may join the [MZAP-LOCAL-GROUP] to listen for
Zone Announcement Messages to build up a list of the scope zones that
are relevant locally, and for Not-Inside Messages if it wishes to learn
nesting information. However, listening to such messages is not the
recommended method for regular applications to discover this
information. These applications will normally query a local Multicast
Address Allocation Server (MAAS) [3], which in turn listens to Zone
Announcement Messages and Not-Inside Messages to maintain scope
information, and can be queried by clients via MADCAP messages.
An entity (including a MAAS) lacking any such information can only
assume that it is within the Global Scope, and the Local Scope, both of
which have well-known address ranges defined in [1].
An internal entity (e.g., an MAAS) receiving a ZAM will parse the
information that is relevant to it, such as the address range, and the
names. An address allocator receiving such information MUST also use
the "B" bit to determine whether it can add the address range to the set
of ranges from which it may allocate addresses (specifically, it may add
them only if the bit is zero). Even if the bit is zero, an MAAS SHOULD
still store the range information so that clients who use relative-
addresses can still obtain the ranges by requesting them from the MAAS.
An internal entity (e.g., an MAAS) may assume that X nests within Y if:
Draft MZAP June 1999
a) it first heard ZAMs for both X and Y at least [NIM-HOLDTIME]
seconds ago, AND
b) it has not heard a NIM indicating that "X not inside Y" for at
least [NIM-HOLDTIME] seconds.
6.2. Sending ZAMs
Each ZBR should send a Zone Announcement Message for each scope zone for Each ZBR should send a Zone Announcement Message for each scope zone for
which it is a boundary every [ZAM-INTERVAL] seconds, +/- 30% of [ZAM- which it is a boundary every [ZAM-INTERVAL] seconds, +/- 30% of [ZAM-
INTERVAL] each time to avoid message synchronisation. INTERVAL] each time to avoid message synchronisation.
Each ZBR should send a Zone Convexity Message for each scope zone for The ZAM packet also contains a Zones Traveled Limit (ZTL). If the
which it is a boundary every [ZCM-INTERVAL] seconds, +/- 30% of [ZCM- number of Local Zone IDs in the ZAM path becomes equal to the Zones
INTERVAL] each time to avoid message synchronisation. Traveled Limit, the packet will be dropped. The ZTL field is set when
the packet is first sent, and defaults to 32, but can be set to a lower
value if a network administrator knows the expected size of the zone.
6.3. Receiving ZAMs
When a ZBR receives a ZAM for some scope zone X, it uses the following
rules.
If the local ZBR does NOT have any configuration for scope X:
(1) Check to see if the included start and end addresses overlap with,
but are not identical to, the start and end addresses of any
locally-configured scope Y, and if so, signal an address range
conflict to a local administrator.
(2) Create a local "X not inside" state entry, if such an entry does
not already exist. The ZBR then restarts the entry's timer at
[ZAM-HOLDTIME]. Existence of this state indicates that the ZBR
knows that X does not nest inside any scope for which it is a
boundary. If the entry's timer expires (because no more ZAMs for X
are heard for [ZAM-HOLDTIME]), the entry is deleted.
If the local ZBR does have configuration for scope X:
(1) If the ZAM originated from OUTSIDE the scope (i.e., received over a
boundary interface for scope X):
Draft MZAP June 1999
a)
If the Scope Zone ID in the ZAM matches the ZBR's own Scope Zone
ID, then signal a leaky scope misconfiguration.
b)
Drop the ZAM (perform no further processing below). For
example, router G in Figure 2 will not forward the ZAM. This
rule is primarily a safety measure, since the placement of G in
Figure 2 is not a recommended configuration, as discussed
earlier.
(2) If the ZAM originated from INSIDE the scope:
a)
Add the Origin to the local list of ZBRs (including the local
ZBR) for scope X, and update the Zone ID is to be the lowest IP
address in the list. Set the ZBR list entry added to time out
after [ZAM-HOLDTIME] if no further messages are received from
that ZBR, so that the Zone ID will converge to the lowest
address of any active ZBR for the scope.
b)
If the Origin's Scope Zone ID in the ZAM does not match the
Scope Zone ID kept by the local ZBR, and this mismatch continues
to occur, then signal a possible leaky scope warning.
c)
For each textual name in the ZAM, see if a name for the same
scope and language is locally-configured; if so, but the scope
names do not match, signal a scope name conflict to a local
administrator.
d)
If the ZAM was received on an interface which is NOT a Local
Scope boundary, and the last Local Zone ID Address in the path
list is 0, the ZBR fills in the Local Zone ID Address of the
local zone from which the ZAM was received.
If a ZAM for the same scope (as identified by the origin Zone ID and
first multicast address) was received in the last [ZAM-DUP-TIME]
seconds, the ZAM is then discarded. Otherwise, the ZAM is cached for at
least [ZAM-DUP-TIME] seconds. For example, when router C in Figure 2
receives the ZAM via B, it will not be forwarded, since it has just
forwarded the ZAM from E.
Draft MZAP June 1999
The Zones Travelled count in the message is then incremented, and if the
updated count is equal to or greater than the ZTL field, schedule a ZLE
to be sent as described in the next subsection and perform no further
processing below.
If the Zone ID of the Local Scope zone in which the ZBR resides is not
already in the ZAM's path list, then the ZAM is immediately re-
originated within the Local Scope zone. It adds its own address and the
Zone ID of the Local Scope zone into which the message is being
forwarded to the ZAM path list before doing so. A ZBR receiving a ZAM
with a non-null path list MUST NOT forward that ZAM back into a Local
Scope zone that is contained in the path list. For example, in Figure
2, router F, which did not get the ZAM via A due to packet loss, will
not forward the ZAM from B back into Zone 2 since the path list has {
(E,1), (A,2), (B,3) } and hence Zone 2 already appears.
In addition, the ZBR re-originates the ZAM out each interface with a
Local Scope boundary (except that it is not sent back out the interface
over which it was received, nor is it sent into any local scope zone
whose ID is known and appears in the path list). In each such ZAM re-
originated, the ZBR adds its own IP address to the path list, as well as
the Zone ID Address of the Local Scope Zone into which the ZAM is being
sent, or 0 if the ID is unknown. (For example, if the other end of a
point-to-point link also has a boundary on the interface, then the link
has no Local Scope Zone ID.)
6.4. Sending ZLEs
This packet is sent by a local-zone boundary router that would have
exceeded the Zone Traveled Limit if it had forwarded a ZAM packet. To
avoid ZLE implosion, ZLEs are multicast with a random delay and
suppressed by other ZLEs. It is only scheduled if at least [ZLE-MIN-
INTERVAL] seconds have elapsed since it previously sent a ZLE to any
destination. To schedule a ZLE, the router sets a random delay timer
within the interval [ZLE-SUPPRESSION-INTERVAL], and listens to the
[MZAP-RELATIVE-GROUP] within the included scope for other ZLEs. If any
are received before the random delay timer expires, the timer is cleared
and the ZLE is not sent. If the timer expires, the router sends a ZLE
to the [MZAP-RELATIVE-GROUP] within the indicated scope.
The method used to choose a random delay (T) is as follows:
Choose a random value X from the uniform random interval [0:1]
Let C = 256
Set T = [ZLE-SUPPRESSION-INTERVAL] log( C*X + 1) / log(C)
Draft MZAP June 1999
This equation results in an exponential random distribution which
ensures that close to one ZBR will respond. Using a purely uniform
distribution would begin to exhibit scaling problems as the number of
ZBRs rose. Since ZLEs are only suppressed if a duplicate ZLE arrives
before the time chosen, two routers choosing delays which differ by an
amount less than the propagation delay between them will both send
messages, consuming excess bandwidth. Hence it is desirable to minimize
the number of routers choosing a delay close to the lowest delay chosen,
and an exponential distribution is suitable for this purpose.
A router SHOULD NOT send more than one Zone Limit Exceeded message every A router SHOULD NOT send more than one Zone Limit Exceeded message every
[ZLE-MIN-INTERVAL] regardless of destination. [ZLE-MIN-INTERVAL] regardless of destination.
Each ZBR should send a Zone State Session Message for each scope zone 6.5. Receiving ZLEs
for which it is a boundary every [ZNSM-INTERVAL] seconds, +/- 30% of
[ZNSM- INTERVAL] each time to avoid message synchronization.
5. Constants When a router receives a ZLE, it performs the following actions:
[MZAP-PORT]: The well-known UDP port to which all MZAP messages are (1) If the router has a duplicate ZLE message scheduled to be sent, it
sent. Value: TBD by IANA. unschedules its own message so another one will not be sent.
Draft MZAP February 1998 (2) If the ZLE contains the router's own address in the Origin field,
it signals a leaky scope misconfiguration.
6.6. Sending ZCMs
Each ZBR should send a Zone Convexity Message (ZCM) for each scope zone
for which it is a boundary every [ZCM-INTERVAL] seconds, +/- 30% of
[ZCM-INTERVAL] each time to avoid message synchronisation.
ZCMs are sent to the [ZCM-RELATIVE-GROUP] in the scoped range itself.
(For example, if the scope range is 239.1.0.0 to 239.1.0.255, then these
messages should be sent to 239.1.0.252.) As these are not Locally-Scoped
packets, they are simply multicast across the scope zone itself, and
require no path to be built up, nor any special processing by
intermediate Local Scope ZBRs.
6.7. Receiving ZCMs
When a ZCM is received for a given scope X, on an interface which is
inside the scope, it follows the rules below:
Draft MZAP June 1999
(1) The Origin is added to the local list of ZBRs (including itself)
for that scope, and the Zone ID is updated to be the lowest IP
address in the list. The new entry is scheduled to be timed out
after [ZCM-HOLDTIME] if no further messages are received from that
ZBR, so that the Zone ID will converge to the lowest address of any
active ZBR for the scope.
(2) If a ZBR is listed in ZCMs received, but the next-hop interface
(according to the multicast RIB) towards that ZBR is outside the
scope zone, or if no ZCM is received from that ZBR for [ZCM-
HOLDTIME] seconds, as in the example in Figure 3, then signal a
non-convexity problem.
(3) For each textual name in the ZCM, see if a name for the same scope
and language is locally-configured; if so, but the scope names do
not match, signal a scope name conflict to a local administrator.
6.8. Sending NIMs
Periodically, for each scope zone Y for which it is a boundary, a router
originates a Not-Inside Message (NIM) for each "X not inside" entry it
has created when receiving ZAMs. Like a ZAM, this message is multicast
to the address [MZAP-LOCAL-GROUP] from one of its interfaces inside Y.
Each ZBR should send such a Not-Inside Message every [NIM-INTERVAL]
seconds, +/- 30% of [NIM-INTERVAL] to avoid message synchronization.
6.9. Receiving NIMs
When a ZBR receives a NIM saying that "X is not inside Y", it is
forwarded, unmodified, in a manner similar to ZAMs:
(1) If the NIM was received on an interface with a boundary for either
X or Y, the NIM is discarded.
(2) Unlike ZAMs, if the NIM was not received on the interface towards
the message origin (according to the Multicast RIB), the NIM is
discarded.
(3) If a NIM for the same X and Y (where each is identified by its
first multicast address) was received in the last [ZAM-DUP-TIME]
seconds, the NIM is not forwarded.
Draft MZAP June 1999
(4) Otherwise, the NIM is cached for at least [ZAM-DUP-TIME] seconds.
(5) The ZBR then re-originates the NIM (i.e., with the original UDP
payload) into each local scope zone in which it has interfaces,
except that it is not sent back into the local scope zone from
which the message was received, nor is it sent out any interface
with a boundary for either X or Y.
7. Constants
[MZAP-PORT]: The well-known UDP port to which all MZAP messages are
sent. Value: 2106.
[MZAP-LOCAL-GROUP]: The well-known group in the Local Scope to which [MZAP-LOCAL-GROUP]: The well-known group in the Local Scope to which
ZAMs are sent. All Multicast Address Allocation servers and Zone Border ZAMs are sent. All Multicast Address Allocation servers and Zone
Routers listen to this group. Value: TBD by IANA. Boundary Routers listen to this group. Value: 239.255.255.252 for IPv4;
FF03:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFC for IPv6.
[ZCM-RELATIVE-GROUP]: The relative group in each scope zone, to which [ZCM-RELATIVE-GROUP]: The relative group in each scope zone, to which
ZCMs are sent. A Zone Border Router listens to the relative group in ZCMs are sent. A Zone Boundary Router listens to the relative group in
each scope for which it is a border. Value: TBD by IANA. each scope for which it is a boundary. Value: (last IP address in scope
range) - 3. For example, in the Local Scope, the relative group is the
same as the [MZAP-LOCAL-GROUP] address.
[ZAM-INTERVAL]: The interval at which a Zone Border Router originates [ZAM-INTERVAL]: The interval at which a Zone Boundary Router originates
Zone Announcement Messages. Default value: 600 seconds (10 minutes). Zone Announcement Messages. Default value: 600 seconds (10 minutes).
[ZAM-HOLDTIME]: The holdtime to include in a ZAM. This SHOULD be set [ZAM-HOLDTIME]: The holdtime to include in a ZAM. This SHOULD be set
to at least 3 * [ZAM-INTERVAL]. Default value: 1860 seconds (31 to at least 3 * [ZAM-INTERVAL]. Default value: 1860 seconds (31
minutes). minutes).
[ZAM-DUP-TIME]: The time interval after forwarding a ZAM, during which [ZAM-DUP-TIME]: The time interval after forwarding a ZAM, during which
ZAMs for the same scope will not be forwarded. Default value: 30 ZAMs for the same scope will not be forwarded. Default value: 30
seconds. seconds.
[ZCM-INTERVAL]: The interval at which a Zone Border Router originates [ZCM-INTERVAL]: The interval at which a Zone Boundary Router originates
Zone Convexity Messages. Default value: 600 seconds (10 minutes). Zone Convexity Messages. Default value: 600 seconds (10 minutes).
[ZCM-HOLDTIME]: The holdtime to include in a ZCM. This SHOULD be set [ZCM-HOLDTIME]: The holdtime to include in a ZCM. This SHOULD be set
to at least 3 * [ZCM-INTERVAL]. Default value: 1860 seconds (31 to at least 3 * [ZCM-INTERVAL]. Default value: 1860 seconds (31
minutes). minutes).
[ZLE-SUPPRESSION-INTERVAL]: The interval over which to choose a random [ZLE-SUPPRESSION-INTERVAL]: The interval over which to choose a random
delay before sending a ZLE message. Default value: 300 seconds (5 delay before sending a ZLE message. Default value: 300 seconds (5
Draft MZAP June 1999
minutes). minutes).
[ZLE-MIN-INTERVAL]: The minimum interval between sending ZLE messages, [ZLE-MIN-INTERVAL]: The minimum interval between sending ZLE messages,
regardless of destination. Default value: 300 seconds (5 minutes). regardless of destination. Default value: 300 seconds (5 minutes).
[NIM-INTERVAL]: The interval at which a Zone Border Router originates [NIM-INTERVAL]: The interval at which a Zone Boundary Router originates
Zone Not Inside Messages. Default value is 1800 seconds (30 minutes) Not-Inside Messages. Default value: 1800 seconds (30 minutes).
[NIM-HOLDTIME]: The holdtime to include the state within a NIM. This [NIM-HOLDTIME]: The holdtime to include the state within a NIM. This
SHOULD be set to at least 3 * [NIM-INTERVAL]. Default value: 5460 (91 SHOULD be set to at least 3 * [NIM-INTERVAL]. Default value: 5460 (91
minutes) minutes)
6. Security Considerations 8. Security Considerations
MZAP does not include authentication in its messages. Thus it is open While unauthorized reading of MZAP messages is relatively innocuous (so
to misbehaving hosts sending spoof ZAMs, ZCMs, or NIMs. encryption is generally not an issue), accepting unauthenticated MZAP
messages can be problematic. Authentication of MZAP messages can be
provided by using the IPsec Authentication Header (AH) [12].
Draft MZAP February 1998 In the case of ZCMs and ZLEs, an attacker can cause false logging of
convexity and leakage problems. It is likely that is would be purely an
annoyance, and not cause any significant problem. (Such messages could
be authenticated, but since they may be sent within large scopes, the
receiver may not be able to authenticate a non-malicious sender.)
In the case of ZCMs, these spoof messages can cause false logging of ZAMs and NIMs, on the other hand, are sent within the Local Scope, where
convexity problems. It is likely that is would be purely an annoyance, assuming a security relationship between senders and receivers is more
and not cause any significant problem. practical.
In the case of ZAMs, spoof messages can also cause false logging of In the case of NIMs, accepting unauthenticated messages can cause the
configuration problems. This is also considered to not be a significant false cancellation of nesting relationships. This would cause a section
problem. of the hierarchy of zones to flatten. Such a flattening would lessen
the efficiency benefits afforded by the hierarchy but would not cause it
to become unusable.
In the case of NIMs, spoof messages can also cause the false Accepting unauthenticated ZAM messages, however, could cause
cancellation of nesting relationships. This would cause a section of the applications to believe that a scope zone exists when it does not. If
hierarchy of zones to flatten. Such a flattening would lessen the these were believed, then applications may choose to use this non-
efficiency benefits afforded by the hierarchy but would not cause it to existent administrative scope for their uses. Such applications would
become unusable. be able to communicate successfully, but would be unaware that their
traffic may be traveling further than they expected. As a result, any
application accepting unauthenticated ZAMs MUST only take scope names as
a guideline, and SHOULD assume that their traffic sent to non-local
scope zones might travel anywhere. The confidentiality of such traffic
Spoofed zone announcements however might cause applications to believe Draft MZAP June 1999
that a scope zone exists when it does not. If these were believed, then
applications may choose to use this non-existent administrative scope CANNOT be assumed from the fact that it was sent to a scoped address
zone for their uses. Such applications would be able to communicate that was discovered using MZAP.
successfully, but would be unaware that their traffic may be traveling
further than they expected. As a result, applications MUST only take
scope names as a guideline, and SHOULD assume that their traffic sent to
non-local scope zones might travel anywhere. The confidentiality of
such traffic CANNOT be assumed from the fact that it was sent to a
scoped address that was discovered using MZAP.
In addition, ZAMs are used to inform Multicast Address Allocation In addition, ZAMs are used to inform Multicast Address Allocation
Servers of names of scopes, and spoofed ZAMs would result in false names Servers (MAASs) of names and address ranges of scopes, and accepting
being presented to users. To counter this, ZAMs may be authenticated as unauthenticated ZAMs could result in false names being presented to
follows: users, and in wrong addresses being allocated to users. To counter
this, MAAS's authenticate ZAMs as follows:
(1) A ZBR signs all ZAMs it originates. (1) A ZBR signs all ZAMs it originates (using an AH).
(2) A ZBR signs a ZAM it forwards if and only if it can authenticate (2) A ZBR signs a ZAM it relays if and only if it can authenticate the
the previous sender. A ZBR MUST still forward un-authenticated previous sender. A ZBR MUST still forward un-authenticated ZAMs
ZAMs (to provide leak detection), but should propagate an (to provide leak detection), but should propagate an authenticated
authenticated ZAM even if an un-authenticated one was received with ZAM even if an un-authenticated one was received with the last
the last [ZAM-DUP-TIME] seconds. [ZAM-DUP-TIME] seconds.
(3) A MAAS SHOULD be configured with the public key of the local zone (3) A MAAS SHOULD be configured with the public key of the local zone
in which it resides. A MAAS thus configured SHOULD ignore an in which it resides. A MAAS thus configured SHOULD ignore an
unauthenticated ZAM if an authenticated one for the same scope has unauthenticated ZAM if an authenticated one for the same scope has
been received, and MAY ignore all unauthenticated ZAMs. been received, and MAY ignore all unauthenticated ZAMs.
Draft MZAP February 1998 9. Acknowledgements
7. References This document is a product of the MBone Deployment Working Group, whose
members provided many helpful comments and suggestions. The Multicast
Address Allocation Working Group also provided useful feedback regarding
scope names and interactions with applications.
10. References
[1] Meyer, D., "Administratively Scoped IP Multicast", RFC 2365, July [1] Meyer, D., "Administratively Scoped IP Multicast", RFC 2365, July
1998. 1998.
[2] Bradner, S., "Key words for use in RFCs to Indicate Requirement [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", RFC 2119, March 1997. Levels", RFC 2119, March 1997.
[3] Handley, M., Thaler, D., and D. Estrin, "The Internet Multicast [3] Handley, M., Thaler, D., and D. Estrin, "The Internet Multicast
Address Allocation Architecture", Internet Draft, Dec 1997. Address Allocation Architecture", Internet Draft, Dec 1997.
[4] Yergeau, F., "UTF-8, a transformation format of ISO 10646", RFC [4] Yergeau, F., "UTF-8, a transformation format of ISO 10646", RFC
2279, January 1998. 2279, January 1998.
Draft MZAP June 1999
[5] Fenner, W., and S. Casner, "A ''traceroute'' facility for IP [5] Fenner, W., and S. Casner, "A ''traceroute'' facility for IP
Multicast", draft-ietf-idmr-traceroute-ipm-02.txt, Internet Draft, Multicast", draft-ietf-idmr-traceroute-ipm-02.txt, Internet Draft,
November 1997. November 1997.
[6] Alvestrand, H., "Tags for the Identification of Languages", RFC [6] Alvestrand, H., "Tags for the Identification of Languages", RFC
1766, March 1995. 1766, March 1995.
[7] Handley, M., "Multicast Address Allocation Protocol (AAP)", draft- [7] Handley, M., "Multicast Address Allocation Protocol (AAP)", draft-
handley-aap-01.txt, Internet Draft, July 1998. handley-aap-01.txt, Internet Draft, July 1998.
[8] Kermode, R. "Scoped Hybrid Automatic Repeat reQuest with Forward [8] Kermode, R. "Scoped Hybrid Automatic Repeat reQuest with Forward
Error Correction (SHARQFEC)", ACM SIGCOMM 98, September 1998, Error Correction (SHARQFEC)", ACM SIGCOMM 98, September 1998,
Vancouver, Canada. Vancouver, Canada.
8. Acknowledgements [9] Patel, B., Shah, M., and S. Hanna. "Multicast Address Dynamic
Client Allocation Protocol (MADCAP)", Work in progress, May 1999.
This document is a product of the MBone Deployment Working Group, whose [10] J. Postel, "Assigned Numbers", RFC 1700, STD 2, October 1994.
members provided many helpful comments and suggestions. The Multicast
Address Allocation Working Group also provided useful feedback regarding
scope names and interactions with applications.
9. Authors' Addresses [11] IANA, "Address Family Numbers", http://www.isi.edu/in-
notes/iana/assignments/address-family-numbers
[12] Kent, S., and R. Atkinson, "IP Authentication Header", RFC 2402,
November 1998.
Draft MZAP June 1999
11. Authors' Addresses
Mark Handley Mark Handley
AT&T Center for Internet Research at ICSI AT&T Center for Internet Research at ICSI
1947 Center St, Suite 600 1947 Center St, Suite 600
Berkely, CA 94704 Berkely, CA 94704
USA USA
Email: mjh@aciri.org Email: mjh@aciri.org
Draft MZAP February 1998
David Thaler David Thaler
Microsoft Microsoft
One Microsoft Way One Microsoft Way
Redmond, WA 98052 Redmond, WA 98052
USA USA
Email: dthaler@microsoft.com Email: dthaler@microsoft.com
Roger Kermode Roger Kermode
Motorola Australian Research Centre Motorola Australian Research Centre
12 Lord St, 12 Lord St,
Botany, NSW 2109 Botany, NSW 2109
Australia Australia
Email: Roger_Kermode@email.mot.com Email: Roger_Kermode@email.mot.com
10. Full Copyright Statement 12. Full Copyright Statement
Copyright (C) The Internet Society (1998). All Rights Reserved. Copyright (C) The Internet Society (1999). All Rights Reserved.
This document and translations of it may be copied and furnished to This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it or others, and derivative works that comment on or otherwise explain it or
assist in its implementation may be prepared, copied, published and assist in its implementation may be prepared, copied, published and
distributed, in whole or in part, without restriction of any kind, distributed, in whole or in part, without restriction of any kind,
provided that the above copyright notice and this paragraph are included provided that the above copyright notice and this paragraph are included
on all such copies and derivative works. However, this document itself on all such copies and derivative works. However, this document itself
may not be modified in any way, such as by removing the copyright notice may not be modified in any way, such as by removing the copyright notice
or references to the Internet Society or other Internet organizations, or references to the Internet Society or other Internet organizations,
except as needed for the purpose of developing Internet standards in except as needed for the purpose of developing Internet standards in
which case the procedures for copyrights defined in the Internet which case the procedures for copyrights defined in the Internet
languages other than English. languages other than English.
The limited permissions granted above are perpetual and will not be The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns. revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an "AS This document and the information contained herein is provided on an "AS
IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK
Draft MZAP June 1999
FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT
LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT
INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR
FITNESS FOR A PARTICULAR PURPOSE." FITNESS FOR A PARTICULAR PURPOSE.
Draft MZAP February 1998
Table of Contents Table of Contents
1 Introduction .................................................... 2 1 Introduction .................................................... 2
2 Overview ........................................................ 3 2 Terminology ..................................................... 4
2.1 Nesting ....................................................... 6 3 Overview ........................................................ 5
3 Usage ........................................................... 8 3.1 Scope Nesting ................................................. 6
3.1 Zone IDs ...................................................... 8 3.2 Other Messages ................................................ 7
3.2 Informing internal entities of scopes ......................... 8 3.3 Zone IDs ...................................................... 7
3.3 Detecting non-convex scope zones .............................. 9 4 Detecting Router Misconfigurations .............................. 8
3.4 Detecting leaky boundaries for non-local scopes ............... 9 4.1 Detecting non-convex scope zones .............................. 8
3.5 Detecting a leaky Local Scope zone ............................ 10 4.2 Detecting leaky boundaries for non-local scopes ............... 9
3.6 Detecting conflicting scope zones ............................. 10 4.3 Detecting a leaky Local Scope zone ............................ 10
3.7 Packet Formats ................................................ 11 4.4 Detecting conflicting scope zones ............................. 10
3.7.1 Zone Announcement Message ................................... 15 5 Packet Formats .................................................. 11
3.7.2 Zone Limit Exceeded (ZLE) ................................... 16 5.1 Zone Announcement Message ..................................... 14
3.7.3 Zone Convexity Message ...................................... 17 5.2 Zone Limit Exceeded (ZLE) ..................................... 15
3.7.4 Not-Inside Message .......................................... 18 5.3 Zone Convexity Message ........................................ 15
4 Message Timing .................................................. 19 5.4 Not-Inside Message ............................................ 16
5 Constants ....................................................... 19 6 Message Processing Rules ........................................ 17
6 Security Considerations ......................................... 20 6.1 Internal entities listening to MZAP messages .................. 17
7 References ...................................................... 22 6.2 Sending ZAMs .................................................. 18
8 Acknowledgements ................................................ 22 6.3 Receiving ZAMs ................................................ 18
9 Authors' Addresses .............................................. 22 6.4 Sending ZLEs .................................................. 20
10 Full Copyright Statement ....................................... 23 6.5 Receiving ZLEs ................................................ 21
6.6 Sending ZCMs .................................................. 21
6.7 Receiving ZCMs ................................................ 21
6.8 Sending NIMs .................................................. 22
6.9 Receiving NIMs ................................................ 22
7 Constants ....................................................... 23
8 Security Considerations ......................................... 24
9 Acknowledgements ................................................ 25
10 References ..................................................... 25
11 Authors' Addresses ............................................. 27
12 Full Copyright Statement ....................................... 27
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