Network Working Group O. Finkelman
Internet-Draft Qwilt
Intended status: Standards Track S. Mishra
Expires: October 2, 2019 Verizon
March 31, 2019
CDNI Request Routing Extensions
draft-ietf-cdni-request-routing-extensions-02
Abstract
The Open Caching working group of the Streaming Video Alliance is
focused on the delegation of video delivery requests from commercial
CDNs to a caching layer at the ISP. In that aspect, Open Caching is
a specific use case of CDNI, where the commercial CDN is the upstream
CDN (uCDN) and the ISP caching layer is the downstream CDN (dCDN).
The extensions specified in this document to the CDNI Metadata and
FCI interfaces are derived from requirements raised by Open Caching
but are applicable to CDNI use cases in general.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 2, 2019.
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Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Redirect Target Address Capability Object . . . . . . . . . . 3
2.1. DnsTarget . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2. HttpTarget . . . . . . . . . . . . . . . . . . . . . . . 6
3. Fallback Target Address Metadata . . . . . . . . . . . . . . 7
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
4.1. CDNI Payload Types . . . . . . . . . . . . . . . . . . . 9
4.1.1. CDNI FCI RedirectTarget Payload Type . . . . . . . . 9
4.1.2. CDNI MI FallbackTarget Payload Type . . . . . . . . . 9
5. Security Considerations . . . . . . . . . . . . . . . . . . . 10
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10
7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 10
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
8.1. Normative References . . . . . . . . . . . . . . . . . . 10
8.2. Informative References . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
This document defines objects needed for Open Caching request
routing. For that purpose it extends CDNI metadata [RFC8006] and
CDNI Footprint and Capabilities [RFC8008]. For consistency, this
document follows the CDNI notation of uCDN (the commercial CDN) and
dCDN (the ISP caching layer).
This document also registers CDNI Payload Types [RFC7736] for the
defined objects:
o Redirect Target Capability (for dCDN advertising redirect target
address)
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o Fallback Target Metadata (for uCDN configuring fallback target
address)
1.1. Terminology
This document reuses the terminology defined in [RFC6707], [RFC8006],
[RFC8007], and [RFC8008].
Additionally, the following terms are used throughout this document
and are defined as follows:
o RR - Request Router
o CP - Content Provider
2. Redirect Target Address Capability Object
Iterative request redirect as defined in section 1.1 of [RFC7336]
requries the provisioning of a redirect target address to be used by
the uCDN in order to redirect to the dCDN. Redirect target addresses
can vary between different footprints, for example between different
regions, and they may also change over time, for example due to
scaling issues a dCDN may need to split different regions over
multiple targets, or due to network problems the dCDN may have to
change the target address. Due to this variable and dynamic nature
of the redirect target, it may not be suitable to advertise it during
bootstrap, and a more dynamic, and footprint oriented interface is
required. Therefore, we have chosen to use the CDNI Footprint and
Capabilities interface for redirect target advertisement.
Use cases
o Footprint: The dCDN may want to have a different target per
footprint. Note that a dCDN may spread across multiple
geographies. This makes it easier to route client requests to a
nearby request router. Though this can be achieved using a single
canonical name and Geo DNS, that approach has limitations; for
example a client may be using third party DNS resolver, making it
impossible for the redirector to detect where the client is
located, or Geo DNS granularity may be too rough for the
requirement of the application.
o Scaling: The dCDN may choose to scale its request routing service
by deploying more request routers in new locations and advertise
them via an updatable interface like the FCI.
The Redirect Target capability object is used to indicate the target
address the uCDN should use in order to redirect a client to the
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dCDN. A target may be attached to a specific uCDN host, a list of
uCDN hosts, or it can be set globally for all the hosts of the uCDN.
When 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
Redirect Target Capability object as "redirecting-hosts". In that
case, the uCDN can redirect to that dCDN address, only if the request
was directed to one of these uCDN hosts.
A redirect target for DNS redirection is an IP address used as an A
record response or a FQDN used as an alias in a CNAME record response
(see [RFC1034]) of the uCDN DNS router. Note that DNS routers take
routing decisions based on either the DNS resolver's IP address or
the client IP address when EDNS0 client-subnet is used (see
[RFC7871]). The dCDN may choose to advertise redirect targets and
footprints to cover both cases. A uCDN DNS router implemenation
SHOULD prefer routing based on client IP address when it is
available.
A redirect target for HTTP redirection is the URI to be used as a
value of the Location header of a HTTP redirect 3xx response,
typically a 302 (Found) (see section 7.1.2 of [RFC7231] and section
6.4 of [RFC7231]).
Property: redirecting-hosts
Description: One or more uCDN hosts to which this redirect
target is attached. A redirecting host SHOULD be a host that
was published in a HostMatch object by the uCDN as defined in
section 4.1.2 of [RFC8006].
Type: A list of Endpoint objects (see section 4.3.3 of
[RFC8006])
Mandatory-to-Specify: No. If not present, or empty, the
redirect target applies to all hosts of the redirecting uCDN.
Property: dns-target
Description: Target address for DNS A record or CNAME record.
Type: DnsTarget object (see Section 2.1)
Mandatory-to-Specify: No. but at least one of "dns-target" or
"http-target" MUST be present and non empty.
Property: http-target
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Description: Target URI for HTTP redirect.
Type: HttpTarget object (see Section 2.2)
Mandatory-to-Specify: No. but at least one of "dns-target" or
"http-target" MUST be present and non empty.
Example of Redirect Target Capability object that advertises a dCDN
target address that is attached to a specific list of uCDN
"redirecting-hosts". A uCDN host that is included in that list can
redirect to the advertised dCDN redirect target.
{
"capabilities": [
{
"capability-type": "FCI.RedirectTarget",
"capability-value": {
"redirecting-hosts": [
"a.service123.ucdn.example.com",
"b.service123.ucdn.example.com"
]
"dns-target": {
"host": "service123.ucdn.example.dcdn.com"
}
"http-target": {
<Properties of an HttpTarget object>
}
},
"footprints": [
<Footprint objects>
]
}
]
}
2.1. DnsTarget
The DnsTarget object gives the instructions to construct the target
address for the DNS response for delegation from the uCDN to the
dCDN.
Property: host
Description: The host property is a hostname or an IP address,
without a port number.
Type: Endpoint object as defined in section 4.3.3 of [RFC8006]
with the limitation that it MUST NOT include a port number.
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Mandatory-to-Specify: Yes.
Example of DnsTarget object:
{
"host": "service123.ucdn.example.dcdn.com"
}
Example of a DNS query for uCDN address
"a.service123.ucdn.example.com" and the corresponding CNAME
redirection response:
Query:
a.service123.ucdn.example.com:
type A, class IN
Response:
a.service123.ucdn.example.com:
type CNAME, class IN, cname service123.ucdn.example.dcdn.com
2.2. HttpTarget
The HttpTarget object gives the instructions to construct the target
Location URI for http redirection from the uCDN to the dCDN.
Property: host
Description: Hostname or IP address and an optional port, i.e.,
the host and port of the authority component of the URI as
described in section 3.2 of [RFC3986].
Type: Endpoint object as defined in section 4.3.3 of [RFC8006].
Mandatory-to-Specify: Yes.
Property: path-prefix
Description: A path prefix for the HTTP redirect Location
header. The original path is appended after this prefix.
Type: A prefix of a path-absolute as defined in section 3.3 of
[RFC3986]. The prefix MUST end with a trailing slash, to
indicate the end of the last path segment in the prefix.
Mandatory-to-Specify: No. If this property is absent or empty,
the uCDN MUST NOT prepend a path prefix to the original content
path, i.e. the original path MUST appear in the location URI
right after the authority component.
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Property: include-redirecting-host
Description: A flag indicating whether or not to include the
redirecting host as the first path segment after the path-
prefix. In case this flag is true and a "path-prefix" is used,
the uCDN redirecting host MUST be added as a separate path
segment after the path-prefix and before the original URL path.
In case this flag is true and there is no path-prefix, the uCDN
redirecting host MUST be prepended as the first path segment in
the redirect URL.
Type: Boolean.
Mandatory-to-Specify: No. Default value is False.
Example of HttpTarget object with a path-prefix and include-
redirecting-host:
{
"host": "us-east1.dcdn.com",
"path-prefix": "/cache/1/",
"include-redirecting-host": true
}
Example of a HTTP request for content at uCDN host
"a.service123.ucdn.example.com" and the corresponding HTTP response
with Location header used for redirecting the client to the dCDN
using the the http-target in the above example:
Request:
GET /vod/1/movie.mp4 HTTP/1.1
Host: a.service123.ucdn.example.com
Response:
HTTP/1.1 302 Found
Location: http://us-east1.dcdn.com/cache/1/
a.service123.ucdn.example.com/vod/1/movie.mp4
3. Fallback Target Address Metadata
Open Caching requires that the uCDN should provide fallback target
server to the dCDN to be used in cases where the dCDN cannot properly
handle the request. To avoid redirect loops, the fallback target
server's address at the uCDN MUST be differnet than the original
address at the uCDN from which the client was redirected to the dCDN.
The uCDN MUST avoid further redirection when receiving the client
request at the fallback target. The fallback target is defined as a
generic metadata object (see section 3.2 of [RFC8006])
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Use cases
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
case of failures or temporary network overload.
o No coverage: A dCDN request router receives a request from a
client located in an area inside the footprint but not covered by
the dCDN caches, or a client located outside the dCDN footprint
coverage. In such cases, the router may choose to redirect the
request back to the uCDN fallback address.
o Error: A cache may receive a request that it cannot properly
serve, for example, some of the metadata objects for that service
were not properly acquired. In this case, the cache may resolve
to redirect back to uCDN.
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
uCDN. Fallback target is represented as endpoint objects as defined
in section 4.3.3 of [RFC8006].
The uCDN fallback target address may be used as a DNS A record or
CNAME record in case of DNS redirection mode or a host name for HTTP
redirect.
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
client would have used for the original uCDN request, stripping, if
needed, the dCDN path-prefix and the uCDN host name from the redirect
URL that may have been used to request the content from the dCDN.
Property: host
Description: Target address to which the dCDN can redirect the
client.
Type: Endpoint object as defined in section 4.3.3 of [RFC8006]
with the limitation that in case of DNS delegation, it MUST NOT
include a port number.
Mandatory-to-Specify: Yes.
Example of a MI.FallbackTarget Metadata object that designates the
host address the dCDN should use as fallback address to redirect back
to the uCDN.
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{
"generic-metadata-type": "MI.FallbackTarget",
"generic-metadata-value":
{
"host": "fallback-a.service123.ucdn.example"
}
}
4. IANA Considerations
4.1. CDNI Payload Types
This document requests the registration of the following CDNI Payload
Types under the IANA CDNI Payload Type registry defined in [RFC7736]:
+--------------------+---------------+
| Payload Type | Specification |
+--------------------+---------------+
| FCI.RedirectTarget | RFCthis |
| MI.FallbackTarget | RFCthis |
+--------------------+---------------+
[RFC Editor: Please replace RFCthis with the published RFC number for
this document.]
4.1.1. CDNI FCI RedirectTarget Payload Type
Purpose: The purpose of this payload type is to distinguish
RedirectTarget FCI objects
Interface: FCI
Encoding: see Section 2
4.1.2. CDNI MI FallbackTarget Payload Type
Purpose: The purpose of this payload type is to distinguish
FallbackTarget MI objects (and any associated capability
advertisement)
Interface: MI/FCI
Encoding: see Section 3
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5. Security Considerations
This specification is in accordance with the CDNI Metadata Interface
and the CDNI Request Routing: Footprint and Capabilities Semantics.
As such, it is subject to the security considerations as defined in
[RFC8006] and [RFC8008] respectively.
6. Acknowledgements
TBD.
7. Contributors
TBD.
8. References
8.1. Normative References
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
<https://www.rfc-editor.org/info/rfc1034>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/info/rfc3986>.
[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
DOI 10.17487/RFC7231, June 2014,
<https://www.rfc-editor.org/info/rfc7231>.
[RFC8006] Niven-Jenkins, B., Murray, R., Caulfield, M., and K. Ma,
"Content Delivery Network Interconnection (CDNI)
Metadata", RFC 8006, DOI 10.17487/RFC8006, December 2016,
<https://www.rfc-editor.org/info/rfc8006>.
[RFC8007] Murray, R. and B. Niven-Jenkins, "Content Delivery Network
Interconnection (CDNI) Control Interface / Triggers",
RFC 8007, DOI 10.17487/RFC8007, December 2016,
<https://www.rfc-editor.org/info/rfc8007>.
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[RFC8008] Seedorf, J., Peterson, J., Previdi, S., van Brandenburg,
R., and K. Ma, "Content Delivery Network Interconnection
(CDNI) Request Routing: Footprint and Capabilities
Semantics", RFC 8008, DOI 10.17487/RFC8008, December 2016,
<https://www.rfc-editor.org/info/rfc8008>.
8.2. Informative References
[RFC6707] Niven-Jenkins, B., Le Faucheur, F., and N. Bitar, "Content
Distribution Network Interconnection (CDNI) Problem
Statement", RFC 6707, DOI 10.17487/RFC6707, September
2012, <https://www.rfc-editor.org/info/rfc6707>.
[RFC7336] Peterson, L., Davie, B., and R. van Brandenburg, Ed.,
"Framework for Content Distribution Network
Interconnection (CDNI)", RFC 7336, DOI 10.17487/RFC7336,
August 2014, <https://www.rfc-editor.org/info/rfc7336>.
[RFC7736] Ma, K., "Content Delivery Network Interconnection (CDNI)
Media Type Registration", RFC 7736, DOI 10.17487/RFC7736,
December 2015, <https://www.rfc-editor.org/info/rfc7736>.
[RFC7871] Contavalli, C., van der Gaast, W., Lawrence, D., and W.
Kumari, "Client Subnet in DNS Queries", RFC 7871,
DOI 10.17487/RFC7871, May 2016,
<https://www.rfc-editor.org/info/rfc7871>.
Authors' Addresses
Ori Finkelman
Qwilt
6, Ha'harash
Hod HaSharon 4524079
Israel
Phone: +972-72-2221647
Email: ori.finkelman.ietf@gmail.com
Sanjay Mishra
Verizon
13100 Columbia Pike
Silver Spring, MD 20904
USA
Email: sanjay.mishra@verizon.com
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