draft-ietf-cdni-request-routing-extensions-05.txt   draft-ietf-cdni-request-routing-extensions-06.txt 
Network Working Group O. Finkelman Network Working Group O. Finkelman
Internet-Draft Qwilt Internet-Draft Qwilt
Intended status: Standards Track S. Mishra Intended status: Standards Track S. Mishra
Expires: February 10, 2020 Verizon Expires: March 26, 2020 Verizon
August 9, 2019 September 23, 2019
CDNI Request Routing Extensions CDNI Request Routing Extensions
draft-ietf-cdni-request-routing-extensions-05 draft-ietf-cdni-request-routing-extensions-06
Abstract Abstract
The Open Caching working group of the Streaming Video Alliance is Open Caching is a use case of Content Delivery Networks
focused on the delegation of video delivery requests from commercial Interconnetion (CDNI) in which the commercial Content Delivery
CDNs to a caching layer at the ISP. In that aspect, Open Caching is Network (CDN) is the upstream CDN (uCDN) and the ISP caching layer
a specific use case of CDNI, where the commercial CDN is the upstream serves as the downstream CDN (dCDN). The extensions specified in
CDN (uCDN) and the ISP caching layer is the downstream CDN (dCDN). this document to the CDNI Metadata and FCI interfaces are derived
The extensions specified in this document to the CDNI Metadata and from requirements raised by Open Caching but are also applicable to
FCI interfaces are derived from requirements raised by Open Caching CDNI use cases in general.
but are applicable to CDNI use cases in general.
Requirements Language Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
document are to be interpreted as described in RFC 2119 [RFC2119]. "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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 February 10, 2020. This Internet-Draft will expire on March 26, 2020.
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.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Redirect Target Capability Object . . . . . . . . . . . . . . 3 2. Redirect Target Capability . . . . . . . . . . . . . . . . . 3
2.1. Properties of Redirect Target Capability Object . . . . . 4 2.1. Properties of Redirect Target Capability Object . . . . . 5
2.2. DnsTarget . . . . . . . . . . . . . . . . . . . . . . . . 6 2.2. DnsTarget . . . . . . . . . . . . . . . . . . . . . . . . 6
2.3. HttpTarget . . . . . . . . . . . . . . . . . . . . . . . 6 2.3. HttpTarget . . . . . . . . . . . . . . . . . . . . . . . 7
3. Fallback Target Address Metadata . . . . . . . . . . . . . . 8 2.4. Usage Example . . . . . . . . . . . . . . . . . . . . . . 9
3.1. Properties Fallback Target Address Metadata Object . . . 9 3. Fallback Target Address Metadata . . . . . . . . . . . . . . 10
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 3.1. Properties of Fallback Target Address Metadata Object . . 11
4.1. CDNI Payload Types . . . . . . . . . . . . . . . . . . . 9 3.2. Usage Example . . . . . . . . . . . . . . . . . . . . . . 12
4.1.1. CDNI FCI RedirectTarget Payload Type . . . . . . . . 10 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
4.1.2. CDNI MI FallbackTarget Payload Type . . . . . . . . . 10 4.1. CDNI Payload Types . . . . . . . . . . . . . . . . . . . 14
5. Security Considerations . . . . . . . . . . . . . . . . . . . 10 4.1.1. CDNI FCI RedirectTarget Payload Type . . . . . . . . 14
5.1. Confidentiality and Privacy . . . . . . . . . . . . . . . 10 4.1.2. CDNI MI FallbackTarget Payload Type . . . . . . . . . 14
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10 5. Security Considerations . . . . . . . . . . . . . . . . . . . 14
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 5.1. Confidentiality and Privacy . . . . . . . . . . . . . . . 15
7.1. Normative References . . . . . . . . . . . . . . . . . . 11 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 15
7.2. Informative References . . . . . . . . . . . . . . . . . 11 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12 7.1. Normative References . . . . . . . . . . . . . . . . . . 15
7.2. Informative References . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction 1. Introduction
This document defines objects needed for Open Caching request The Open Caching working group of the Streaming Video Alliance (SVA)
routing. For that purpose it extends CDNI metadata [RFC8006] and is focused on the delegation of video delivery requests from
CDNI Footprint and Capabilities [RFC8008]. For consistency, this commercial CDNs to a caching layer at the Internet Service Provider's
document follows the CDNI notation of uCDN (the commercial CDN) and (ISP) network. Open Caching is a specific use case of CDNI where the
dCDN (the ISP caching layer). commercial CDN is the upstream CDN (uCDN) and the ISP caching layer
is the downstream CDN (dCDN). This document defines and registers
CDNI generic metadata object [RFC8006] and CDNI Footprint and
Capabilities object [RFC8008] that are required for Open Caching
request routing. For consistency with other CDNI documents this
document follows the CDNI convention of uCDN (upstream CDN) and dCDN
(downstream CDN) to represent the commerical CDN and ISP caching
layer respectively.
This document also registers CDNI Payload Types [RFC7736] for the This document also registers CDNI Payload Types [RFC7736] for the
defined objects: defined objects:
o Redirect Target Capability (for dCDN advertising redirect target o Redirect Target Capability (for dCDN advertising redirect target
address) address)
o Fallback Target Metadata (for uCDN configuring fallback target o Fallback Target Metadata (for uCDN configuring fallback target
address) address)
1.1. Terminology 1.1. Terminology
This document reuses the terminology defined in [RFC6707], [RFC8006], The following terms are used throughout this document:
[RFC8007], and [RFC8008].
Additionally, the following terms are used throughout this document o FQDN - Fully Qualified Domain Name
and are defined as follows:
o RR - Request Router o CDN - Content Delivery Network
o CP - Content Provider Additionaly, this document reuses the terminology defined in
[RFC6707], [RFC7336], [RFC8006], [RFC8007], and [RFC8008].
Specifically, we use the following CDNI acronyms:
2. Redirect Target Capability Object o FCI - Footprint and Capability Interface (see [RFC8008])
Iterative request redirect as defined in section 1.1 of [RFC7336] o MI - Metadata Interface (see [RFC8006])
requries the provisioning of a redirect target address to be used by
the uCDN in order to redirect to the dCDN. Redirect target addresses o uCDN, dCDN - Upstream CDN and Downstream CDN respectively (see
can vary between different footprints, for example, between different [RFC7336])
regions, and they may also change over time, for example as a result
of network problems. Given this variable and dynamic nature of the o RT - Redirection Target. Endpoint for redirection from uCDN to
redirect target, it may not be suitable to advertise it during dCDN.
bootstrap. A more dynamic and footprint oriented interface is
required. Therefore, we have chosen to use the CDNI Footprint and o RR - Request Router. An element responsible for routing user
Capabilities interface for redirect target advertisement. requests.
2. Redirect Target Capability
Iterative request redirection is defined in Section 1.1 of [RFC7336]
and elaborated by examples in Sections 3.2 and 3.4 of [RFC7336]. A
Redirection Target (RT) is defined in Section 2 of [RFC7975] for
Recursive Request Redirection as:
"The endpoint to which the User Agent is redirected. In CDNI, a
RT may point to a number of different components, some examples
include a surrogate in the same CDN as the request router, a
request router in a dCDN, or a surrogate in a dCDN".
In this document we adopt the same defintion of the RT for the
Iterative Request Redirect use case. This use case requires the
provisioning of the RT address to be used by the uCDN in order to
redirect to the dCDN. RT addresses can vary between different
footprints, for example, between different regions, and they may also
change over time, for example as a result of network problems. Given
this variable and dynamic nature of the redirect target address, it
may not be suitable to advertise it during bootstrap. A more dynamic
and footprint oriented interface is required. Section 4.3 of
[RFC7336] suggests that it could be one of the roles of the FCI
[RFC8008]. Following this suggestion we have, therefore, chosen to
use the CDNI Footprint and Capabilities interface for redirect target
address advertisement.
Use cases Use cases
o Footprint: The dCDN may want to have a different target per o Footprint: The dCDN may want to have a different target per
footprint. Note that a dCDN may spread across multiple footprint. Note that a dCDN may spread across multiple
geographies. This makes it easier to route client requests to a geographies. This makes it easier to route client requests to a
nearby request router. Though this can be achieved using a single nearby request router. Though this can be achieved using a single
canonical name and Geo DNS, that approach has limitations; for canonical name and Geo DNS, that approach has limitations; for
example a client may be using a third party DNS resolver, making example a client may be using a third party DNS resolver, making
it impossible for the redirector to detect where the client is it impossible for the redirector to detect where the client is
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by deploying more request routers in new locations and advertise by deploying more request routers in new locations and advertise
them via an updatable interface like the FCI. them via an updatable interface like the FCI.
The Redirect Target capability object is used to indicate the target The Redirect Target capability object is used to indicate the target
address the uCDN should use in order to redirect a client to the address the uCDN should use in order to redirect a client to the
dCDN. A target may be attached to a specific uCDN host, a list of dCDN. A target may be attached to a specific uCDN host, a list of
uCDN hosts, or used globally for all the hosts of the uCDN. uCDN hosts, or used globally for all the hosts of the uCDN.
When a dCDN is attaching the redirect target to a specific uCDN host When a dCDN is attaching the redirect target to a specific uCDN host
or a list of uCDN hosts, the dCDN MUST advertise the hosts within the or a list of uCDN hosts, the dCDN MUST advertise the hosts within the
Redirect Target capability object as "redirecting-hosts". In that Redirect Target capability object as "redirecting-hosts". In this
case, the uCDN can redirect to that dCDN address, only if the request case, the uCDN can redirect to that dCDN address, only if the User
was directed to one of those uCDN hosts. Agent request was to one of these uCDN hosts.
A redirect target for DNS redirection is an IP address used as an A A redirect target for DNS redirection is an IPv4 address used as an A
record response or a FQDN used as an alias in a CNAME record response record response, an IPv6 address used as an AAAA record response or a
(see [RFC1034]) of the uCDN DNS router. Note that DNS routers make FQDN used as an alias in a CNAME record response (see [RFC1034]) of
routing decisions based on either the DNS resolver's IP address or the uCDN DNS router. Note that DNS routers make routing decisions
the client IP address when EDNS0 client-subnet is used (see based on either the DNS resolver's IP address or the client IP
[RFC7871]). The dCDN may choose to advertise redirect targets and address when EDNS0 client-subnet is used (see [RFC7871]). The dCDN
footprints to cover both cases. A uCDN DNS router implemenation may choose to advertise redirect targets and footprints to cover both
SHOULD prefer routing based on client IP address when it is cases. A uCDN DNS router implemenation SHOULD prefer routing based
available. on client IP address when it is available.
A redirect target for HTTP redirection is the URI to be used as the A redirect target for HTTP redirection is the URI to be used as the
value for the Location header of a HTTP redirect 3xx response, value for the Location header of a HTTP redirect 3xx response,
typically a 302 (Found) (see section 7.1.2 of [RFC7231] and section typically a 302 (Found) (see Section 7.1.2 of [RFC7231] and section
6.4 of [RFC7231]). 6.4 of [RFC7231]).
If the redirect target capability object does not contain a target or
the target is empty, the uCDN MUST interpret it as "no target
available for these uCDN hosts for the specified footprint". In case
such a target was already advertised in a previous FCI object, the
uCDN MUST interperet it as an update that deletes the previous
redirect target.
2.1. Properties of Redirect Target Capability Object 2.1. Properties of Redirect Target Capability Object
The Redirect Target capability object consists of the following The Redirect Target capability object consists of the following
properties: properties:
Property: redirecting-hosts Property: redirecting-hosts
Description: One or more uCDN hosts to which this redirect Description: One or more uCDN hosts to which this redirect
target is attached. A redirecting host SHOULD be a host that target is attached. A redirecting host SHOULD be a host that
was published in a HostMatch object by the uCDN as defined in was published in a HostMatch object by the uCDN as defined in
section 4.1.2 of [RFC8006]. Section 4.1.2 of [RFC8006].
Type: A list of Endpoint objects (see section 4.3.3 of Type: A list of Endpoint objects (see Section 4.3.3 of
[RFC8006]) [RFC8006])
Mandatory-to-Specify: No. If not present, or empty, the Mandatory-to-Specify: No. If not present, or empty, the
redirect target applies to all hosts of the redirecting uCDN. redirect target applies to all hosts of the redirecting uCDN.
Property: dns-target Property: dns-target
Description: Target address for a DNS A record or CNAME record. Description: Target address for a DNS A record, AAAA record or
CNAME record.
Type: DnsTarget object (see Section 2.2) Type: DnsTarget object (see Section 2.2)
Mandatory-to-Specify: No. but at least one of "dns-target" or Mandatory-to-Specify: No. If the dns-target is not present or
"http-target" MUST be present and non-empty. empty the uCDN MUST interpret it as "no dns-target available".
Property: http-target Property: http-target
Description: Target URI for a HTTP redirect. Description: Target URI for a HTTP redirect.
Type: HttpTarget object (see Section 2.3) Type: HttpTarget object (see Section 2.3)
Mandatory-to-Specify: No, but at least one of "dns-target" or Mandatory-to-Specify: No. If the http-target is not present or
"http-target" MUST be present and non-empty. empty the uCDN MUST interpret it as "no http-target available".
The following is an example of a Redirect Target capability object The following is an example of a Redirect Target capability object
serialization that advertises a dCDN target address that is attached serialization that advertises a dCDN target address that is attached
to a specific list of uCDN "redirecting-hosts". A uCDN host that is to a specific list of uCDN "redirecting-hosts". A uCDN host that is
included in that list can redirect to the advertised dCDN redirect included in that list can redirect to the advertised dCDN redirect
target. target. The capabilities object is serialized as a JSON object as
defined in Section 5 of [RFC8008]
{ {
"capabilities": [ "capabilities": [
{ {
"capability-type": "FCI.RedirectTarget", "capability-type": "FCI.RedirectTarget",
"capability-value": { "capability-value": {
"redirecting-hosts": [ "redirecting-hosts": [
"a.service123.ucdn.example.com", "a.service123.ucdn.example.com",
"b.service123.ucdn.example.com" "b.service123.ucdn.example.com"
], ],
skipping to change at page 6, line 11 skipping to change at page 7, line 4
} }
] ]
} }
2.2. DnsTarget 2.2. DnsTarget
The DnsTarget object gives the target address for the DNS response to The DnsTarget object gives the target address for the DNS response to
delegate from the uCDN to the dCDN. delegate from the uCDN to the dCDN.
Property: host Property: host
Description: The host property is a hostname or an IP address, Description: The host property is a hostname or an IP address,
without a port number. without a port number.
Type: Endpoint object as defined in section 4.3.3 of [RFC8006] Type: Endpoint object as defined in Section 4.3.3 of [RFC8006]
with the limitation that it SHOULD NOT include a port number with the limitation that it SHOULD NOT include a port number
and, in case a port number is present, the uCDN MUST ignore it. and, in case a port number is present, the uCDN MUST ignore it.
Mandatory-to-Specify: Yes. Mandatory-to-Specify: Yes.
The following is an example of DnsTarget object: The following is an example of DnsTarget object:
{ {
"host": "service123.ucdn.dcdn.example.com" "host": "service123.ucdn.dcdn.example.com"
} }
skipping to change at page 6, line 48 skipping to change at page 7, line 40
2.3. HttpTarget 2.3. HttpTarget
The HttpTarget object gives the necessary information to construct The HttpTarget object gives the necessary information to construct
the target Location URI for HTTP redirection. the target Location URI for HTTP redirection.
Property: host Property: host
Description: Hostname or IP address and an optional port, i.e., Description: Hostname or IP address and an optional port, i.e.,
the host and port of the authority component of the URI as the host and port of the authority component of the URI as
described in section 3.2 of [RFC3986]. described in Section 3.2 of [RFC3986].
Type: Endpoint object as defined in section 4.3.3 of [RFC8006]. Type: Endpoint object as defined in Section 4.3.3 of [RFC8006].
Mandatory-to-Specify: Yes. Mandatory-to-Specify: Yes.
Property: path-prefix Property: path-prefix
Description: A path prefix for the HTTP redirect Location Description: A path prefix for the HTTP redirect Location
header. The original path is appended after this prefix. header. The original path is appended after this prefix.
Type: A prefix of a path-absolute as defined in section 3.3 of Type: A prefix of a path-absolute as defined in Section 3.3 of
[RFC3986]. The prefix MUST end with a trailing slash, to [RFC3986]. The prefix MUST end with a trailing slash, to
indicate the end of the last path segment in the prefix. indicate the end of the last path segment in the prefix.
Mandatory-to-Specify: No. If this property is absent or empty, Mandatory-to-Specify: No. If this property is absent or empty,
the uCDN MUST NOT prepend a path prefix to the original content the uCDN MUST NOT prepend a path prefix to the original content
path, i.e., the original path MUST appear in the location URI path, i.e., the original path MUST appear in the location URI
right after the authority component. right after the authority component.
Property: include-redirecting-host Property: include-redirecting-host
skipping to change at page 8, line 14 skipping to change at page 9, line 5
Request: Request:
GET /vod/1/movie.mp4 HTTP/1.1 GET /vod/1/movie.mp4 HTTP/1.1
Host: a.service123.ucdn.example.com Host: a.service123.ucdn.example.com
Response: Response:
HTTP/1.1 302 Found HTTP/1.1 302 Found
Location: http://us-east1.dcdn.example.com/cache/1/ Location: http://us-east1.dcdn.example.com/cache/1/
a.service123.ucdn.example.com/vod/1/movie.mp4 a.service123.ucdn.example.com/vod/1/movie.mp4
2.4. Usage Example
Before requests can be routed from the uCDN to the dCDN the CDNs must
exchange service configurations between them. Using the MI the uCDN
advertises out-of-band its hosts to the dCDN, each host is designated
by a host name and has its own specific metadata (see Section 4.1.2
of [RFC8006]. The dCDN, using the FCI, advertises, also out-of-band,
the redirect target address object defined in Section 2.1 for the
relevant uCDN hosts. The following is a generalized example of the
message flow between an upstream CDN and a downstream dCDN. For
simplicity, we focus on the sequence of messages between the uCDN and
dCDN and not on how they are passed.
dCDN uCDN
+ +
| |
(1) | MI: host: s123.ucdn.example.com |
| host-metadata: < metadata > |
<-------------------------------------------------------+
| |
(2) | FCI: capability-type: FCI.RedirectTarget |
| redirecting-hosts: us-east1.dcdn.example.com |
| target host: s123.ucdn.example.com |
+------------------------------------------------------->
| |
| |
+ +
Figure 1: Redirect target address advertisement
1. The uCDN advertises a host (s123.ucdn.example.com) with the host
metadata.
2. The dCDN adveritses its FCI objects to the uCDN including a
FCI.RedirectTarget object that contains the redirect target
address (us-east1.dcdn.example.com) specified for that uCDN host.
Once the redirect target has been set, the uCDN can start redirecting
user requests to the dCDN. The following is a generic sequence of
redirection using the host and redirect target that were advertised
in Figure 1 above.
End User dCDN uCDN RR
+ + +
| | |
(1) | Request sent s123.ucdn.example.com |
+-----------------------+----------------------->
| | |
(2) | Redirect to us-east1.dcdn.example.com |
<-----------------------+-----------------------+
| | |
(3) | Request us-east1.dcdn.example.com |
+-----------------------> |
| | |
(4) | Response | |
<-----------------------+ |
| | |
+ + +
Figure 2: Generic requests redirection sequence
1. The End User sends a request (DNS or HTTP) to the uCDN Request
Router (RR).
2. Using the previously advertised Redirect Target, the uCDN
redirects the request to the dCDN.
3. The End User sends a request to the dCDN.
4. The dCDN either sends a response or reroutes it, for example, to
a dCDN surrogate.
3. Fallback Target Address Metadata 3. Fallback Target Address Metadata
Open Caching requires that the uCDN provide a fallback target server Open Caching requires that the uCDN provides a fallback target server
to the dCDN, to be used in cases where the dCDN cannot properly to the dCDN, to be used in cases where the dCDN cannot properly
handle the request. To avoid redirect loops, the fallback target handle the request. To avoid redirect loops, the fallback target
server's address at the uCDN MUST be differnet from the original uCDN server's address at the uCDN MUST be different from the original uCDN
address from which the client was redirected to the dCDN. The uCDN address from which the client was redirected to the dCDN. The uCDN
MUST avoid further redirection when receiving the client request at MUST avoid further redirection when receiving the client request at
the fallback target. The fallback target is defined as a generic the fallback target. The fallback target is defined as a generic
metadata object (see section 3.2 of [RFC8006]) metadata object (see Section 3.2 of [RFC8006])
Use cases Use cases
o Failover: A dCDN request router receives a request but has no o Failover: A dCDN request router receives a request but has no
caches to which it can route the request. This can happen in the caches to which it can route the request. This can happen in the
case of failures or temporary network overload. case of failures or temporary network overload.
o No coverage: A dCDN request router receives a request from a o No coverage: A dCDN request router receives a request from a
client located in an area inside the footprint but not covered by client located in an area inside the footprint but not covered by
the dCDN caches or outside the dCDN footprint coverage. In such the dCDN caches or outside the dCDN footprint coverage. In such
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o Error: A cache may receive a request that it cannot properly o Error: A cache may receive a request that it cannot properly
serve, for example, some of the metadata objects for that service serve, for example, some of the metadata objects for that service
were not properly acquired. In this case, the cache may resolve were not properly acquired. In this case, the cache may resolve
to redirect back to uCDN. to redirect back to uCDN.
The Fallback target metadata object is used to indicate the target The Fallback target metadata object is used to indicate the target
address the dCDN should use in order to redirect a client back to the address the dCDN should use in order to redirect a client back to the
uCDN. Fallback target is represented as endpoint objects as defined uCDN. Fallback target is represented as endpoint objects as defined
in section 4.3.3 of [RFC8006]. in section 4.3.3 of [RFC8006].
The uCDN fallback target address may be used as a DNS A record or The uCDN fallback target address may be used as a DNS A record, AAAA
CNAME record in case of DNS redirection or a hostname for HTTP record or CNAME record in case of DNS redirection or a hostname for
redirect. HTTP redirect.
When using HTTP redirect to route a client request back to the uCDN, When using HTTP redirect to route a client request back to the uCDN,
it is the dCDN's responsibility to use the original URL path as the it is the dCDN's responsibility to use the original URL path as the
client would have used for the original uCDN request, stripping, if client would have used for the original uCDN request, stripping, if
needed, the dCDN path-prefix and/or the uCDN hostname from the needed, the dCDN path-prefix and/or the uCDN hostname from the
redirect URL that may have been used to request the content from the redirect URL that may have been used to request the content from the
dCDN. dCDN.
3.1. Properties Fallback Target Address Metadata Object 3.1. Properties of Fallback Target Address Metadata Object
The MI.FallbackTarget Metadata object consists of the following The MI.FallbackTarget Metadata object consists of the following
single property: single property:
Property: host Property: host
Description: Target address to which the dCDN can redirect the Description: Target address to which the dCDN can redirect the
client. client.
Type: Endpoint object as defined in section 4.3.3 of [RFC8006] Type: Endpoint object as defined in Section 4.3.3 of [RFC8006]
with the limitation that in case of DNS delegation it SHOULD with the limitation that in case of DNS delegation it SHOULD
NOT include a port number and, in case a port number is NOT include a port number and, in case a port number is
present, the dCDN MUST ignore it. present, the dCDN MUST ignore it.
Mandatory-to-Specify: Yes. Mandatory-to-Specify: Yes.
Example of a MI.FallbackTarget Metadata object that designates the Example of a MI.FallbackTarget Metadata object that designates the
host address the dCDN should use as fallback address to redirect back host address the dCDN should use as fallback address to redirect back
to the uCDN. to the uCDN.
{ {
"generic-metadata-type": "MI.FallbackTarget", "generic-metadata-type": "MI.FallbackTarget",
"generic-metadata-value": "generic-metadata-value":
{ {
"host": "fallback-a.service123.ucdn.example" "host": "fallback-a.service123.ucdn.example"
} }
} }
3.2. Usage Example
The uCDN advertises out-of-band the fallback target address to the
dCDN, so that the dCDN may redirect a request back to the uCDN in
case the dCDN cannot serve it. Using the MI the uCDN advertises its
hosts to the dCDN, along with their specific host metadata (see
Section 4.1.2 of [RFC8006]. The Fallback Target generic metadata
object is encapsulated within the "host-metadata" property of each
host. The following is an example of a message flow between an
upstream CDN and a downstream dCDN. For simplicity, we focus on the
sequence of messages between the uCDN and dCDN, not on how they are
passed.
dCDN uCDN
+ +
| |
(1) | MI: host: s123.ucdn.example.com |
| host-metadata: |
| < metadata objects > |
| < MI.FallbackTarget |
| host: fallback-a.service123.ucdn.example > |
| < metadata objects > |
<-------------------------------------------------------+
| |
(2) | FCI: capability-type: FCI.RedirectTarget |
| redirecting-hosts: us-east1.dcdn.example.com |
| target host: s123.ucdn.example.com |
+------------------------------------------------------->
| |
| |
+ +
Figure 3: Advertisement of host metadata with Fallback Target
1. The uCDN advertises a host (s123.ucdn.example.com) with the host
metadata. The host-metadata property contains a
MI.FallbackTarget object.
2. The dCDN adveritses its FCI objects to the uCDN including a
FCI.RedirectTarget object that contains the redirect target
address (us-east1.dcdn.example.com) specified for that uCDN host.
The following is a generic sequence of redirection using the
configurations that were advertised in Figure 3 above. In this case
the dCDN redirects back to the uCDN fallback target address.
End User dCDN uCDN fallback uCDN RR
+ + + +
| | | |
(1) | Request sent s123.ucdn.example.com | |
+-------------------+-------------------+------------------->
| | | |
(2) | Redirect to us-east1.dcdn.example.com | |
<-------------------+-------------------+-------------------+
| | | |
(3) | Request us-east1.dcdn.example.com | |
+-------------------> | |
| | | |
(4) | Redirect back to fallback-a.service123.ucdn.example |
<-------------------+ | |
| | | |
(5) | Request fallback-a.service123.ucdn.example |
+---------------------------------------> |
| | | |
(6) | Response | | |
<-------------------+-------------------+ |
| | | |
+ + + +
Figure 4: Redirection to Fallback Target
1. The End User sends a request (DNS or HTTP) to the uCDN Request
Router (RR).
2. Using the previously advertised Redirect Target, the uCDN
redirects the request to the dCDN.
3. The End User sends a request to the dCDN.
4. The dCDN cannot handled the request and, therefore, redirects it
back to the uCDN fallback target address.
5. The End User sends the request to the uCDN fallback target
address.
6. The uCDN either sends a response or reroutes it, for example, to
a uCDN surrogate.
4. IANA Considerations 4. IANA Considerations
4.1. CDNI Payload Types 4.1. CDNI Payload Types
This document requests the registration of the following CDNI Payload This document requests the registration of the following CDNI Payload
Types under the IANA "CDNI Payload Types" registry defined in Types under the IANA "CDNI Payload Types" registry defined in
[RFC7736]: [RFC7736]:
+--------------------+---------------+ +--------------------+---------------+
| Payload Type | Specification | | Payload Type | Specification |
skipping to change at page 10, line 47 skipping to change at page 15, line 17
The redirect Target FCI object potentially exposes information about The redirect Target FCI object potentially exposes information about
the internal strcture of the dCDN network. A third party could the internal strcture of the dCDN network. A third party could
intercept the FCI transactions and use the information to attack the intercept the FCI transactions and use the information to attack the
dCDN. An implemenation of the FCI MUST therefore use strong dCDN. An implemenation of the FCI MUST therefore use strong
authentication and encryption and strictly follow the directions for authentication and encryption and strictly follow the directions for
securing the interface as defined for the Metadata Interface in securing the interface as defined for the Metadata Interface in
Section 8.3 of [RFC8006]. Section 8.3 of [RFC8006].
6. Acknowledgements 6. Acknowledgements
The authors thank Nir B. Sopher for reality checks against The authors thank Nir B. Sopher for reality checks against production
production use cases, his contribution is significant to this use cases, his contribution is significant to this document. The
document. The authors also thank Ben Niven-Jenkins for his review authors also thank Ben Niven-Jenkins for his review and feedback and
and feedback and Kevin J. Ma for his guidance throughout the Kevin J. Ma for his guidance throughout the development of this
development of this document including his regular reviews. document including his regular reviews.
7. References 7. References
7.1. Normative References 7.1. Normative References
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities", [RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987, STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
<https://www.rfc-editor.org/info/rfc1034>. <https://www.rfc-editor.org/info/rfc1034>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
skipping to change at page 11, line 28 skipping to change at page 15, line 46
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66, Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005, RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/info/rfc3986>. <https://www.rfc-editor.org/info/rfc3986>.
[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer [RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Semantics and Content", RFC 7231, Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
DOI 10.17487/RFC7231, June 2014, DOI 10.17487/RFC7231, June 2014,
<https://www.rfc-editor.org/info/rfc7231>. <https://www.rfc-editor.org/info/rfc7231>.
[RFC7975] Niven-Jenkins, B., Ed. and R. van Brandenburg, Ed.,
"Request Routing Redirection Interface for Content
Delivery Network (CDN) Interconnection", RFC 7975,
DOI 10.17487/RFC7975, October 2016,
<https://www.rfc-editor.org/info/rfc7975>.
[RFC8006] Niven-Jenkins, B., Murray, R., Caulfield, M., and K. Ma, [RFC8006] Niven-Jenkins, B., Murray, R., Caulfield, M., and K. Ma,
"Content Delivery Network Interconnection (CDNI) "Content Delivery Network Interconnection (CDNI)
Metadata", RFC 8006, DOI 10.17487/RFC8006, December 2016, Metadata", RFC 8006, DOI 10.17487/RFC8006, December 2016,
<https://www.rfc-editor.org/info/rfc8006>. <https://www.rfc-editor.org/info/rfc8006>.
[RFC8007] Murray, R. and B. Niven-Jenkins, "Content Delivery Network [RFC8007] Murray, R. and B. Niven-Jenkins, "Content Delivery Network
Interconnection (CDNI) Control Interface / Triggers", Interconnection (CDNI) Control Interface / Triggers",
RFC 8007, DOI 10.17487/RFC8007, December 2016, RFC 8007, DOI 10.17487/RFC8007, December 2016,
<https://www.rfc-editor.org/info/rfc8007>. <https://www.rfc-editor.org/info/rfc8007>.
[RFC8008] Seedorf, J., Peterson, J., Previdi, S., van Brandenburg, [RFC8008] Seedorf, J., Peterson, J., Previdi, S., van Brandenburg,
R., and K. Ma, "Content Delivery Network Interconnection R., and K. Ma, "Content Delivery Network Interconnection
(CDNI) Request Routing: Footprint and Capabilities (CDNI) Request Routing: Footprint and Capabilities
Semantics", RFC 8008, DOI 10.17487/RFC8008, December 2016, Semantics", RFC 8008, DOI 10.17487/RFC8008, December 2016,
<https://www.rfc-editor.org/info/rfc8008>. <https://www.rfc-editor.org/info/rfc8008>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
7.2. Informative References 7.2. Informative References
[RFC6707] Niven-Jenkins, B., Le Faucheur, F., and N. Bitar, "Content [RFC6707] Niven-Jenkins, B., Le Faucheur, F., and N. Bitar, "Content
Distribution Network Interconnection (CDNI) Problem Distribution Network Interconnection (CDNI) Problem
Statement", RFC 6707, DOI 10.17487/RFC6707, September Statement", RFC 6707, DOI 10.17487/RFC6707, September
2012, <https://www.rfc-editor.org/info/rfc6707>. 2012, <https://www.rfc-editor.org/info/rfc6707>.
[RFC7336] Peterson, L., Davie, B., and R. van Brandenburg, Ed., [RFC7336] Peterson, L., Davie, B., and R. van Brandenburg, Ed.,
"Framework for Content Distribution Network "Framework for Content Distribution Network
Interconnection (CDNI)", RFC 7336, DOI 10.17487/RFC7336, Interconnection (CDNI)", RFC 7336, DOI 10.17487/RFC7336,
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