draft-ietf-mboned-driad-amt-discovery-03.txt		draft-ietf-mboned-driad-amt-discovery-04.txt
	Mboned J. Holland		Mboned J. Holland
	Internet-Draft Akamai Technologies, Inc.		Internet-Draft Akamai Technologies, Inc.
	Updates: 7450 (if approved) April 04, 2019		Updates: 7450 (if approved) April 22, 2019
	Intended status: Standards Track		Intended status: Standards Track
	Expires: October 6, 2019		Expires: October 24, 2019
	DNS Reverse IP AMT Discovery		DNS Reverse IP AMT Discovery
	draft-ietf-mboned-driad-amt-discovery-03		draft-ietf-mboned-driad-amt-discovery-04
	Abstract		Abstract
	This document updates RFC 7450 (Automatic Multicast Tunneling, or		This document updates RFC 7450 (Automatic Multicast Tunneling, or
	AMT) by extending the relay discovery process to use a new DNS		AMT) by extending the relay discovery process to use a new DNS
	resource record named AMTRELAY when discovering AMT relays for		resource record named AMTRELAY when discovering AMT relays for
	source-specific multicast channels. The reverse IP DNS zone for a		source-specific multicast channels. The reverse IP DNS zone for a
	multicast sender's IP address is configured to use AMTRELAY resource		multicast sender's IP address is configured to use AMTRELAY resource
	records to advertise a set of AMT relays that can receive and forward		records to advertise a set of AMT relays that can receive and forward
	multicast traffic from that sender over an AMT tunnel.		multicast traffic from that sender over an AMT tunnel.
	skipping to change at page 1, line 37 ¶		skipping to change at page 1, line 37 ¶
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at https://datatracker.ietf.org/drafts/current/.		Drafts is at https://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	This Internet-Draft will expire on October 6, 2019.		This Internet-Draft will expire on October 24, 2019.
	Copyright Notice		Copyright Notice
	Copyright (c) 2019 IETF Trust and the persons identified as the		Copyright (c) 2019 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(https://trustee.ietf.org/license-info) in effect on the date of		(https://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	skipping to change at page 9, line 29 ¶		skipping to change at page 9, line 29 ¶
	However, the concept of an AMT connection in the context of a Happy		However, the concept of an AMT connection in the context of a Happy
	Eyeballs algorithm is a useful one, and so this section provides the		Eyeballs algorithm is a useful one, and so this section provides the
	following normative definition:		following normative definition:
	o An AMT connection is completed successfully when the gateway		o An AMT connection is completed successfully when the gateway
	receives from a newly discovered relay a valid Membership Query		receives from a newly discovered relay a valid Membership Query
	message (Section 5.1.4 of [RFC7450]) that does not have the L flag		message (Section 5.1.4 of [RFC7450]) that does not have the L flag
	set.		set.
	See Section 2.5.5 for further information about the relevance of the		See Section 2.5.5 of this document for further information about the
	L flag to the establishment of a Happy Eyeballs connection.		relevance of the L flag to the establishment of a Happy Eyeballs
			connection.
	2.4. Optimal Relay Selection		2.4. Optimal Relay Selection
	2.4.1. Overview		2.4.1. Overview
	The reverse source IP DNS query of an AMTRELAY RR is a good way for a		The reverse source IP DNS query of an AMTRELAY RR is a good way for a
	gateway to discover a relay that is known to the sender.		gateway to discover a relay that is known to the sender.
	However, it is NOT necessarily a good way to discover the best relay		However, it is NOT necessarily a good way to discover the best relay
	for that gateway to use, because the RR will only provide information		for that gateway to use, because the RR will only provide information
	skipping to change at page 11, line 17 ¶		skipping to change at page 11, line 17 ¶
	a Happy Eyeballs algorithm to reduce the join latency, while still		a Happy Eyeballs algorithm to reduce the join latency, while still
	prioritizing network efficiency considerations over Address Selection		prioritizing network efficiency considerations over Address Selection
	considerations.		considerations.
	Section 4 of [RFC8305] requires a Happy Eyeballs algorithm to sort		Section 4 of [RFC8305] requires a Happy Eyeballs algorithm to sort
	the addresses with the Destination Address Selection defined in		the addresses with the Destination Address Selection defined in
	Section 6 of [RFC6724], but for the above reasons, that requirement		Section 6 of [RFC6724], but for the above reasons, that requirement
	is superseded in the AMT discovery use case by the following		is superseded in the AMT discovery use case by the following
	considerations:		considerations:
	1. Prefer Local Relays		o Prefer Local Relays
	Figure 5 and Section 3.1.2 provide a motivating example to prefer		Figure 5 and Section 3.1.2 provide a motivating example to prefer
	DNS-SD [RFC6763] for discovery strictly ahead of using the		DNS-SD [RFC6763] for discovery strictly ahead of using the
	AMTRELAY RR controlled by the sender for AMT discovery.		AMTRELAY RR controlled by the sender for AMT discovery.
	For this reason, it's RECOMMENDED that AMT gateways by default		For this reason, it's RECOMMENDED that AMT gateways by default
	perform service discovery using DNS Service Discovery (DNS-SD)		perform service discovery using DNS Service Discovery (DNS-SD)
	[RFC6763] for _amt._udp.<domain> (with <domain> chosen as		[RFC6763] for _amt._udp.<domain> (with <domain> chosen as
	described in Section 11 of [RFC6763]) and use the AMT relays		described in Section 11 of [RFC6763]) and use the AMT relays
	discovered that way in preference to AMT relays discoverable via		discovered that way in preference to AMT relays discoverable via
	the mechanism defined in this document (DRIAD).		the mechanism defined in this document (DRIAD).
	2. Prefer Relays Managed by the Containing Network		o Prefer Relays Managed by the Containing Network
	When no local relay is discoverable with DNS-SD, it still may be		When no local relay is discoverable with DNS-SD, it still may be
	the case that a relay local to the receiver is operated by the		the case that a relay local to the receiver is operated by the
	network providing transit services to the receiver.		network providing transit services to the receiver.
	In this case, when the network cannot make the relay discoverable		In this case, when the network cannot make the relay discoverable
	via DNS-SD, the network SHOULD use the well-known anycast		via DNS-SD, the network SHOULD use the well-known anycast
	addresses from Section 7 of [RFC7450] to route discovery traffic		addresses from Section 7 of [RFC7450] to route discovery traffic
	to the relay most appropriate to the receiver's gateway.		to the relay most appropriate to the receiver's gateway.
	Accordingly, the gateway SHOULD by default discover a relay with		Accordingly, the gateway SHOULD by default discover a relay with
	the well-known AMT anycast addresses as the second preference		the well-known AMT anycast addresses as the second preference
	after DNS-SD when searching for a local relay.		after DNS-SD when searching for a local relay.
	3. Let Sender Manage Relay Provisioning		o Let Sender Manage Relay Provisioning
	A related motivating example in the sending-side network is		A related motivating example in the sending-side network is
	provided by considering a sender which needs to instruct the		provided by considering a sender which needs to instruct the
	gateways on how to select between connecting to Figure 6 or		gateways on how to select between connecting to Figure 6 or
	Figure 7 (from Section 3.2), in order to manage load and failover		Figure 7 (from Section 3.2), in order to manage load and failover
	scenarios in a manner that operates well with the sender's		scenarios in a manner that operates well with the sender's
	provisioning strategy for horizontal scaling of AMT relays.		provisioning strategy for horizontal scaling of AMT relays.
	In this example about the sending-side network, the precedence		In this example about the sending-side network, the precedence
	field described in Section 4.2.1 is a critical method of control		field described in Section 4.2.1 is a critical method of control
	so that senders can provide the appropriate guidance to gateways		so that senders can provide the appropriate guidance to gateways
	during the discovery process.		during the discovery process.
	Therefore, after DNS-SD, the precedence from the RR MUST be used		Therefore, after DNS-SD, the precedence from the RR MUST be used
	for sorting preference ahead of the Destination Address Selection		for sorting preference ahead of the Destination Address Selection
	ordering from Section 6 of [RFC6724], so that only relay IPs with		ordering from Section 6 of [RFC6724], so that only relay IPs with
	the same precedence are directly compared according to the		the same precedence are directly compared according to the
	Destination Address Selection ordering.		Destination Address Selection ordering.
	Accordingly, AMT gateways SHOULD by default prefer relays first by		Accordingly, AMT gateways SHOULD by default prefer relays in this
	DNS-SD if available, then with the anycast addresses defined in		order:
	Section 7 of [RFC7450] (namely: 192.52.193.1 and 2001:3::1), then by
	DRIAD as described in this document (in precedence order, as		1. DNS-SD
	described in Section 4.2.1).		2. Anycast addresses from Section 7 of [RFC7450]
			3. DRIAD
	This default behavior MAY be overridden by administrative		This default behavior MAY be overridden by administrative
	configuration where other behavior is more appropriate for the		configuration where other behavior is more appropriate for the
	gateway within its network.		gateway within its network.
	Among relay addresses that have an equivalent preference as described		Among relay addresses that have an equivalent preference as described
	above, a Happy Eyeballs algorithm for AMT MUST use the Destination		above, a Happy Eyeballs algorithm for AMT MUST use the Destination
	Address Selection defined in Section 6 of [RFC6724], as required by		Address Selection defined in Section 6 of [RFC6724], as required by
	[RFC8305].		[RFC8305].
	Among relay addresses that still have an equivalent preference after		Among relay addresses that still have an equivalent preference after
	the above orderings, a gateway MUST make a non-deterministic choice		the above orderings, a gateway MUST make a non-deterministic choice
	for relay preference ordering, in order to support load balancing by		for relay preference ordering, in order to support load balancing by
	DNS configurations that provide many relay options. (Note that		DNS configurations that provide many relay options.
	gateways not implementing a Happy Eyeballs algorithm are not required
	to use the Destination Address Selection ordering, but are still		The gateway MAY introduce a bias in the non-deterministic choice
	required to use non-deterministic ordering among equally preferred		according to network topology or timing information obtained out of
	relays.)		band or from a historical record. The collection of this information
			is out of scope for this document, but a gateway in possession of
			such information MAY use it to prefer topologically closer relays.
	Note also that certain relay addresses may be excluded from		Note also that certain relay addresses may be excluded from
	consideration by the hold-down timers described in Section 2.5.4.1 or		consideration by the hold-down timers described in Section 2.5.4.1 or
	Section 2.5.5. These relays constitute "unusable destinations" under		Section 2.5.5. These relays constitute "unusable destinations" under
	Rule 1 of the Destination Address Selection, and are also not part of		Rule 1 of the Destination Address Selection, and are also not part of
	the superseding considerations described above.		the superseding considerations described above.
	The discovery and connection process for the relay addresses in the		The discovery and connection process for the relay addresses in the
	above described ordering MAY operate in parallel, subject to delays		above described ordering MAY operate in parallel, subject to delays
	prescribed by the Happy Eyeballs requirements described in Section 5		prescribed by the Happy Eyeballs requirements described in Section 5
	skipping to change at page 13, line 14 ¶		skipping to change at page 13, line 16 ¶
	2.4.3. Connecting to Multiple Relays		2.4.3. Connecting to Multiple Relays
	In some deployments, it may be useful for a gateway to connect to		In some deployments, it may be useful for a gateway to connect to
	multiple upstream relays and subscribe to the same traffic, in order		multiple upstream relays and subscribe to the same traffic, in order
	to support an active/active failover model. A gateway SHOULD NOT be		to support an active/active failover model. A gateway SHOULD NOT be
	configured to do so without guaranteeing that adequate bandwidth is		configured to do so without guaranteeing that adequate bandwidth is
	available.		available.
	A gateway configured to do this SHOULD still use the same preference		A gateway configured to do this SHOULD still use the same preference
	ordering logic from Section 2.4.2 for both connections. (Note that		ordering logic from Section 2.4.2 for each connection. (Note that
	this ordering allows for overriding by explicit administrative		this ordering allows for overriding by explicit administrative
	configuration where required.)		configuration where required.)
	2.5. Guidelines for Restarting Discovery		2.5. Guidelines for Restarting Discovery
	2.5.1. Overview		2.5.1. Overview
	It's expected that gateways deployed in different environments will		It's expected that gateways deployed in different environments will
	use a variety of heuristics to decide when it's appropriate to		use a variety of heuristics to decide when it's appropriate to
	restart the relay discovery process, in order to meet different		restart the relay discovery process, in order to meet different
	skipping to change at page 22, line 48 ¶		skipping to change at page 22, line 48 ¶
	capabilities of the network in Figure 3.		capabilities of the network in Figure 3.
	3.2. Example Sending Networks		3.2. Example Sending Networks
	3.2.1. Sender-controlled Relays		3.2.1. Sender-controlled Relays
	When a sender network is also operating AMT relays to distribute		When a sender network is also operating AMT relays to distribute
	multicast traffic, as in Figure 6, each address could appear as an		multicast traffic, as in Figure 6, each address could appear as an
	AMTRELAY RR for the reverse IP of the sender, or one or more domain		AMTRELAY RR for the reverse IP of the sender, or one or more domain
	names could appear in AMTRELAY RRs, and the AMT relay addresses can		names could appear in AMTRELAY RRs, and the AMT relay addresses can
	be discovered by finding a A or AAAA records from those domain names.		be discovered by finding A or AAAA records from those domain names.
	Sender Network		Sender Network
	+-----------------------------------+		+-----------------------------------+
	| |		| |
	| +--------+ +=======+ +=======+ |		| +--------+ +=======+ +=======+ |
	| | Sender | | AMT | | AMT | |		| | Sender | | AMT | | AMT | |
	| +--------+ | relay | | relay | |		| +--------+ | relay | | relay | |
	| | +=======+ +=======+ |		| | +=======+ +=======+ |
	| | | | |		| | | | |
	| +-----+------+----------+ |		| +-----+------+----------+ |
End of changes. 20 change blocks.
	55 lines changed or deleted		59 lines changed or added
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