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Content DistributionInternetworking
IETF BOF
December 12, 2000
Phil RzewskiGary Tomlinson
Content Networking
• Using IETF “application layer” protocols as transport– e.g. HTTP, RTSP
• Routing & forwarding of requests & responses instead of packets
Example Content Network: Hierarchical caching
ISP
client
“edge” / “access”caches
“parent”cache(s)
• Typically static forwarding rules– HTTP parenting– ICP
• Example request forwarding– Single path– Redundant– URL partitioning
foo.combar.com
Example Content Network:Content Distribution Network (CDN)s
CDN
client
“surrogates”
“request-routing”system(s)
• Request routing systems map a client to a surrogate– e.g. DNS
• Example request forwarding– Ask another surrogate– Seek origin
Local DNS
Content Distribution Internetworking
CDN
ISP
• Interconnect Content Networks• Different administrative domains• Different technologies
Content Distribution Internetworking
• Area of CDI interest lies in communication across these boundaries• Details within each Content Network should be irrelevant
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Key Terms&
Concepts
Surrogate“A delivery server, other than the origin. Receives a mapped
request and delivers the corresponding content.”
client
Content Network
surrogate
origin
Delivery“The activity of presenting a
publisher’s content forconsumption by a client.”
delivery
Distribution“The activity of moving a publisher’s content from
its origin to one or more surrogates.
CNorigin
CN
CN
Injection(aka “origin distribution peering”)
“Publishing of content into one-or-moreContent Networks by origins.”
Content Signal“A message delivered through a distribution systemthat specifies information about an item of content.”
e.g. to indicate the origin has a new version ofsome piece of content
Request-Routing“The activity of steering or directing a request from a
client to a suitable surrogate.”
CN
CN
client
Accounting“Measurement and recording of distribution and delivery activities,
especially when the information recorded is ultimately used as a basis for the subsequent transfer of money, goods, or obligations”
CN
CN
CN
Drafting teams
• Two design teams produced 8 of the 9 drafts
• The two teams were aligned with Content Bridge & Content Alliance
• Sharing and cooperation developed late so there is some overlap
Understandingthe Strawman
Drafts
draft-day-cdnp-model-04.txt• Introduction, background, & vocabulary on
CDNs– CDN examples provided
• Introduction & vocabulary on developing CDN interconnection technology– CDN peering examples provided
– Content Peering Gateways (CPG) defined
• Some high-level operational considerations included
draft-day-cdnp-scenarios-02.txt• Used to collect the communities of interest
requirements• Describes representative configurations that
can be realized when internetworking CDNs.
• Framed by the concepts:– CONTENT has value– DISTRIBUTION has value– CLIENTS have value
draft-green-cdnp-gen-arch-02.txt
• Presents three main architectural elements– Request-Routing Peering System– Distribution Peering System– Accounting Peering System
• For each architectural element, presents:– Known requirements– Problems that need further investigation
• Security considerations
draft-green-cdnp-gen-arch-02.txtConceptual View of Peered CDNs
CPG CPG
CPG
CDN ARequest-Routing
Distribution
Accounting
CDN BRequest-Routing
Distribution
Accounting
CDN CRequest-Routing
Distribution
Accounting
surrogatessurrogates
surrogates
clients
draft-green-cdnp-gen-arch-02.txtRequest-Routing Peering System Architecture
Surrogates
CDN A
client
AuthoritativeRequest-Routing
System
Request-RoutingSystem
CDN C
Request-RoutingCPG
Request-RoutingSystem
Request-RoutingCPG
Request-RoutingCPG
Surrogate Surrogates
CDN B
Request-RoutingCPG
Request-RoutingSystem
Surrogate Surrogates
(1st Level)
(2nd Level)
Inter-CDN Request-Routing
Inter-CDN Recursive Request-Routing
draft-cain-cdnp-known-request-routing-00.txt• Presents known mechanisms to direct client
requests to surrogate servers.– DNS request-routing– Transport-layer request-routing– Application-layer request-routing
• Discusses measurements, metrics, and feedback
draft-deleuze-cdnp-dnsmap-peer-00.txt• Proposes a DNS-based Mapping
System• Focused on determining the next hop
toward the appropriate surrogate• Describes an approach using CNAME• Proposes naming criteria to describe
– Delivery service– Delivery Footprint
draft-green-cdnp-gen-arch-02.txtDistribution Peering System Architecture
Surrogates
CDN A
Origin
DistributionSystem
CDN C
DistributionCPG
DistributionSystem
DistributionCPG
DistributionCPG
Surrogate Surrogates
CDN B
DistributionCPG
DistributionSystem
Surrogates
Origin Distribution Peering
Inter-CDN Distribution Peering
DistributionCPG
draft-green-cdnp-gen-arch-02.txtAccounting Peering System Architecture
Surrogates
CDN A
Origin
AccountingSystem
CDN C
AccountingCPG
AccountingSystem
AccountingCPG
AccountingCPG
Surrogate Surrogates
CDN B
AccountingCPG
AccountingSystem
Surrogates
Origin Accounting Peering
Inter-CDN Accounting Peering
AccountingCPG
BillingOrganization
Billing Accounting Peering
draft-gilletti-cdnp-aaa-reqs-00.txt• Requirements for CDN Accounting Peering
– Framed against ongoing work of AAA WG• Details on CDN Accounting Peering models
– Additional terminology– Transaction models– Accounting messaging
• Lists problems to be solved
draft-rzewski-oacp-00.txt
• Origin/Access Content Peering for HTTP
• Specific (“vertical”) implementation proposal of a way to pass control & accounting between origin & access endpoints.
– Roles described for specific types of content networks (Hoster/CDN, Operator, Access Provider)
• Note Request- Routing is a “null case” in the implementation
New Content Published by Content Provider Content signals for changed URLs sent to Content Relay at Hoster/CDN Content signals for changed URLs forwarded to Content Relay at Operator Content signals for changed URLs forwarded to Content Relay Surrogate at Access
Provider Changed content may be retrieved by Content Relay at Access Provider (HTTP GET) Content signals for changed URLs forwarded to Access Caches Access clients request content from Access Caches, if it is not in Access Cache, content is
pulled from Content Gateway Surrogate (parent cache)
draft-rzewski-oacp-00.txtAccess Provider (ISP)Hoster/CDN
Content Relay
ContentInjector
ContentRelay
Surrogate
AccessCaches
Origin
Content Relay
Operator
www.com
AccessClients
draft-rzewski-cndistcs-00.txt• Proposes specific content signals
– HTTP DELETE method for “invalidation”
– Also additional “CND: GET” header to kick off pre-load
Log info is collected and summarized at Access Caches in regular intervals
Access log info is collated at Accounting Relay at Access Provider
Access log information centralized & passed through Operator for settlement and billing
Near real-time summaries are forwarded to Accounting Gateway at Hoster/CDN
draft-rzewski-oacp-00.txtISP 1
Hoster/CDN
AccountingRelay
AccountingRelay
SummaryLogging
AccessCachesOrigin
ISP 2
AccountingRelay
SummaryLogging
AccessCaches
OperatorAccounting
Relay
Settlement& Billing
Access Providers (ISPs)
AccessClients
draft-rzewski-cnacct-00.txt• Proposes SQUID-like summary log
format• Proposes using HTTP POST to pass
log information between networks
OrganizationGoing Forward
Possible Informal StructureModels
ScenariosArchitectureFramework
“umbrella”
AccountingKnown methods
Requirement specificationsProposed protocols
Implementation debate
DistributionKnown methods
Requirement specificationsProposed protocols
Implementation debate
Request-RoutingKnown methods
Requirement specificationsProposed protocols
Implementation debate
“communities of interest”
Other WGs
AAA
WEBI
DNSext
.
.
.