ALTO H. Song
Internet-Draft Huawei
Intended status: Standards Track M. Tomsu
Expires: December 28, 2010 Alcatel-lucent Bell Labs
G. Garcia
Telefonica I+D
Y. Wang
Microsoft Corp.
V. Pascual
Tekelec
June 26, 2010
ALTO Service Discovery
draft-song-alto-server-discovery-02
Abstract
Application-Layer Traffic Optimization (ALTO) service aims to provide
distributed applications with information to perform better-than-
random initial peer selection when multiple peers in the network are
available to provide a resource or service. In order to discover an
Application-Layer Traffic Optimization (ALTO) Server, a set of
mechanisms are required. These mechanisms enable applications to
find an information source which provides them with information
regarding the underlying network. This document discusses various
scenarios of ALTO discovery and specifies the use of several
available options such as DHCP or DNS.
Status of this Memo
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 28, 2010.
Copyright Notice
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Copyright (c) 2010 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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. History . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. ALTO Service Deployment . . . . . . . . . . . . . . . . . . . 5
3.1. ISP-Centric vs. Application-Specific ALTO Service
Deployments . . . . . . . . . . . . . . . . . . . . . . . 6
3.2. Cross-domain vs. Localized ALTO Server Discovery . . . . . 8
4. ALTO Service Discovery Scenarios . . . . . . . . . . . . . . . 8
4.1. Discovery Metrics . . . . . . . . . . . . . . . . . . . . 8
4.1.1. Discovery Clients . . . . . . . . . . . . . . . . . . 8
4.1.2. Service Location . . . . . . . . . . . . . . . . . . . 9
4.1.3. Layering Perspective . . . . . . . . . . . . . . . . . 9
4.2. Discovery Scenarios . . . . . . . . . . . . . . . . . . . 9
4.2.1. Local ALTO service discovery by end terminals . . . . 10
4.2.2. Local ALTO service discovery by application
trackers . . . . . . . . . . . . . . . . . . . . . . . 10
5. ALTO Service Discovery Mechanisms . . . . . . . . . . . . . . 11
5.1. ALTO service discovery using Domain Name System (DNS) . . 12
5.1.1. DNS-based ALTO discovery . . . . . . . . . . . . . . . 12
5.1.2. Determine Service Name of Local ALTO servers . . . . . 13
5.1.2.1. Using DHCP option for access domain name . . . . . 13
5.1.2.2. Use IANA Database . . . . . . . . . . . . . . . . 14
5.1.2.3. Reverse DNS lookup . . . . . . . . . . . . . . . . 14
5.2. DHCP . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5.3. XRD . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5.4. Provisioning . . . . . . . . . . . . . . . . . . . . . . . 15
5.5. Manual Configuration . . . . . . . . . . . . . . . . . . . 15
5.6. Multicast and broadcast . . . . . . . . . . . . . . . . . 15
5.7. Caching . . . . . . . . . . . . . . . . . . . . . . . . . 16
6. Security Considerations . . . . . . . . . . . . . . . . . . . 16
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 17
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
9.1. Normative References . . . . . . . . . . . . . . . . . . . 17
9.2. Informative References . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19
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1. Introduction
1.1. History
This document represents a merge of features from two previous
drafts:
(1). draft-wang-alto-discovery-00
(2). draft-song-alto-server-discovery-00
The ALTO service architecture and protocol are currently under
discussion and development within the IETF ALTO working group.
Although it is identified in the charter that a discovery mechanism
is needed, the preference is to adopt one or more existing mechanisms
for ALTO discovery rather than designing a new one. Note though
certain design decisions of the final ALTO framework will affect the
selection of discovery mechanisms. As a result, this document makes
minimum assumptions of the ALTO framework, and presents different
scenarios and available options based on prior and related discovery
mechanisms. This document will be updated to track the progress of
the ALTO requirements and solution.
1.2. Overview
The ALTO problem statement draft [I-D.ietf-alto-problem-statement]
describes that in P2P applications or client/server applications,
resources or services are often available through multiple replicas
and each of those are sometimes provided by different providers.
ALTO service gives guidance to a consumer or directory about which
resource provider(s) to select, in order to optimize the client's
performance or quality of experience while optimizing resource
consumption in the underlying network infrastructure.
In order to query the ALTO server, clients must first know one or
more ALTO servers that might provide useful information. The purpose
of the ALTO discovery mechanism is to find those servers in different
network and application scenarios.
Section 3 and Section 4 discuss various scenarios of ALTO service
deployment and discovery. Section 5 provides a description of
available discovery mechanisms and its application to the ALTO
service discovery use case addressing potential issues and
consideration for each.
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2. Terminology
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 [RFC2119].
The document uses terms defined in [I-D.ietf-alto-problem-statement].
In addition to the generic ALTO descriptions, the following terms are
used to describe the discovery mechanisms in this document:
o ALTO Discovery Client: The logical entity discovering the ALTO
Service. Depending on the scenario, this could be a Peer or a Super-
peer/Tracker.
o ALTO Discovery Server: The logical entity providing information to
locate the ALTO Service. Depending on the discovery mechanism, this
could be another Peer or a dedicated entity in the network.
o ALTO Discovery Domain: The scope of the network handled by a
particular ALTO Discovery Server.
3. ALTO Service Deployment
This section explores the various dimensions of the ALTO service
deployment and access scenarios, and briefly discusses their
implications to the discovery mechanisms. Figure 1 below shows a
generic ALTO framework diagram with discovery. .
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+------+
+-----+ | Peers
+-----+ +------+ +=====| |--+-oo
| |......| |====+ oo+--*--+ o
+-----+ +------+ | o * ooooooo
Source of ALTO | o *
Topological Service | o +--*--+
information +===o=| | Tracker
o +-----+ /Super-peer
ALTO Discovery o o
Service o o
+------+ o o
| |oooooooooo
+------+
Legend:
=== ALTO query protocol
ooo ALTO service discovery protocol
*** Application protocol (out of scope)
... Provisioning or initialization (out of scope)
Figure 1 ALTO Discovery Diagram
3.1. ISP-Centric vs. Application-Specific ALTO Service Deployments
An ALTO Server is the logical entity that provides query interfaces
for ALTO Clients. ALTO servers can be deployed in an ISP-centric
deployment or on the application level by application providers or
other trusted third parties:
1. A network operator which wants to optimize its traffic, e.g. to
reduce its transit traffic volume across the network boundaries; a
third party on behalf of one or even several ISPs.
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+-----------+ +-----------+ +---------+
|ALTO Server| |ALTO Server| |ALTO |
| A | | B | |Service |
+-----------+ +-----------+ |Discovery|
^ ^ +---------+
+---+--+ +---+--+ o o
+|------|-------------------|------|-+ o o
|| | P2P Appication A | | |ooo o
++------+-------------------+------+-+ o
| | | | o
++------+-------------------+------+-+ o
|| | P2P Applcation B | | |oooooooo
++------+-------------------+------+-+
|ISP A | .............. | ISP B|
+------+ +------+
Figure 2: ISP-centric ALTO service deployment example
2. The application provider itself, a trusted third party or a user
community: acting on the application level and spanning different
networks. They run distributed algorithms to measure the overall
network through some mechanisms and provide an ALTO service to
numerous application clients. However in this case, the application
level service may not know the policy of network operators, so with
high probability it will also cause suboptimal result for the network
operator while benefitting the applications. (Haibin: not the main
focus of this WG? Need to update or remove from the spec)
+---------+
+-----------+ |ALTO |
|ALTO Server| |Service |
+-----------+ |Discovery|
^ ^ +---------+
+------+ | | +------+ o o
+|------|--+---------|------|------|-+ o o
|| | P2P Appication A | | |ooo o
++------+------------+------+------+-+ o
| | | | | o
++------+------------|------+------+-+ o
|| | P2P Applcation B | | |oooooooo
++------+-------------------+------+-+
|ISP A | .............. | ISP B|
+------+ +------+
Figure 3: Application-centric ALTO service deployment example
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3.2. Cross-domain vs. Localized ALTO Server Discovery
For cross domain scenarios, the ALTO service includes the ALTO
servers provided by p2p application community as well as the ALTO
servers provided by a third party on behalf of multiple cooperating
network operators.
So there may be several ALTO servers distributed in different
operator's networks.
Each operator may provide the ALTO service using their own ALTO
servers. Each network operator may have its own traffic optimization
policy based on his network topology, however it may not know other
network operator's policies, nor be clear of other network operator's
topologies (e.g. topology hiding). Each of the ALTO servers may have
a FQDN.
The ALTO client (e.g. the Tracker) must be able to discover and
choose the ALTO server that has the information that is specific to
those clients located within that network.
In localized discovery deployments one or several ALTO servers
provide the service only to clients in their own network or
autonomous system.
4. ALTO Service Discovery Scenarios
4.1. Discovery Metrics
4.1.1. Discovery Clients
The ALTO Client can be the Peer in the end-user host or an external
entity like a Super-peer or Resource Directory (aka Tracker) on
behalf of the Peer [I-D.ietf-alto-problem-statement]. If a Super-
Peer or Tracker acts as an ALTO Client it needs to know and select
the suitable ALTO Service for the Peer being served. Possible
mechanisms for third party ALTO discovery have been proposed
in[I-D.kiesel-alto-3pdisc]
In a hybrid model the location of the ALTO Server could be
communicated from the Peer to the Super-Peer using the application
protocol. It could also be discovered by the Super-Peer from other
Peer information received implicitly (like the Peer public IP
address) or received explicitly.
There could be scenarios where only the Peer (and not the Super-Peer/
Tracker) is able to access the ALTO Service, for example if the ALTO
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Server is located in a private network.
4.1.2. Service Location
The ALTO service could be provided in a distributed and cooperative
fashion by the Peers in an overlay, or it can be provided by a
centralized entity (the ALTO Server) for a given scope. In the
former case, a DHT-style key-based routing algorithm could be used to
locate the peers with the target network information in this type of
distributed environment. For the latter case, where a centralized
ALTO Server is implicitly or explicitly assigned to a specific
network scope, an out-of-band discovery mechanism is often required.
All current ALTO solution proposals, ([Infoexp],
[I-D.wang-alto-p4p-specification]), fall into the second category.
The ALTO Server for a Peer could be in the same Local Area Network
(LAN), within the same ISP Network but not on the same LAN, or in the
Global Internet outside the ISP Network. Different network scopes
place different constraints on the discovery mechanisms. Multicast
discovery generally works within a single LAN only, whereas DNS-based
or DHCP-based discovery can span multiple subnets within a single ISP
or a single network administrative domain. Internet scope discovery
usually requires cross-domain indexing or directory services. Note
that peers participating in a single P2P application may reside on
the same or different ISP networks. Scenarios like this may require
hybrid discovery solutions that can adapt to multiple network scopes
at the same time. The discovery mechanisms listed in this document
should take into account possible limitations of the ALTO service
deployment in those network scopes.
4.1.3. Layering Perspective
The discovery process takes place before the first access to the ALTO
server. This discovery process could be done at host network
initialization time, at application initialization time or just
before the first ALTO query is sent.
4.2. Discovery Scenarios
The ALTO service discovery scenarios are classified into two types:
one is the ALTO server providing service to the overall network, and
the other is where the ALTO server is providing service to the local
network.
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4.2.1. Local ALTO service discovery by end terminals
In p2p applications without a tracker like DHTs and other
conventional client/server applications, an end device needs to
discover the local ALTO server by itself.
After the discovery of an ALTO server, the p2p client can get
guidance from the ALTO server directly or through its application
tracker.
+---------------+
| ALTO Server |
+---------------+
^ ^ +-----------+
| | | ALTO |
| +---+---+ | Service |
| |tracker| | Discovery |
| +-------+ +---------+-+
| | o o
+------------+--+ | o o
|P2P Application|ooooo|oooooooooooo o
| Client A | | o
+---------------+ | o
| o
+--+-------------+ o
| P2P Application|oooooo
| Client B |
+----------------+
Figure 4: Local ALTO service discovery by end terminals (Example)
4.2.2. Local ALTO service discovery by application trackers
Some p2p applications have trackers, and these applications don't
need to have their clients looking for the ALTO server guidance.
Trackers query the ALTO servers for guidance, and then return the
final ranked result to the application clients. However, application
clients are distributed among different network operators and
autonomous systems. Trackers must find different ALTO servers for
the clients located in different network operators or autonomous
systems.
Figure 5 shows an example for a tracker's ALTO server discovery. For
client 1, the tracker has not cached yet the mapping between client
1's network operator and its ALTO server address, so it queries the
DNS server for the ALTO server address in that operator's domain.
And then the tracker interacts with the ALTO server on behalf of
client 1, finally, the ranked list is sent back to client 1. For
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client 2, the tracker has cached the mapping between client 2's
network operator and its ALTO server address, so it does not need to
query the DNS for the address of ALTO server 2.
+-------------+ +-------------+
| ALTO Server1| | ALTO Server2|
+-------------+ +-------------+
^ | ^ |
3| 4| b| |c
| | | |
v /----------+-\ v
+---+ ////// \\\\\
| | ||| |||
| |<--->| |
|DNS| 2 | Application Tracker |
| | ||| |||
| | \\\\\\ /////
+---+ ^ | \------------/ |
| |5 ^ |d
1| | a| |
| v | v
+-+---------+ +---+--------+
|Application| |Application |
|client1 | |client2 |
+-----------+ +------------+
Figure 5: Local ALTO service discovery by application trackers (Example)
5. ALTO Service Discovery Mechanisms
One ALTO client should use one or several of the introduced discovery
mechanisms according to its application scenario until it finally
finds an appropriate ALTO server.
The following issues should be considered when designing the ALTO
service discovery mechanism.
Load Balance: When more than one ALTO server provide identical
service for the same area, we must find a mechanism to balance the
processing load between the ALTO servers;
Well known port: If ALTO server provides service through a well
known port, then the discovery mechanism only needs to discover
the IP address of an ALTO server that can provide service for a
client, otherwise, the discovery mechanism must discover both IP
address and port number through which the ALTO server provides the
service.
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Note:It will depend on the ALTO protocol whether a well know
port is used for the ALTO server. If there is no well known
port for the ALTO server, we need to discover the port
information with the discovery process.
IP address change: The IP address of the ALTO server may change in
some circumstances. The ALTO service discovery mechanism must be
well adaptable to this case when necessary.
Mobile Scenarios: When the end terminals are mobile equipments,
the data traffic may route via a roaming client's home agent's
router to the client, or route to the client directly. Which ALTO
server to choose should depend on the routing optimization mode
adopted for mobility. If the data traffic routes via the client's
home agent, it should choose the ALTO server that serves its home
area network, otherwise, it should choose the ALTO server that
serves its current network.
5.1. ALTO service discovery using Domain Name System (DNS)
DNS is widely used on the Internet to discover the server address for
applications. ALTO service is a conventional client/server mode
service, which can use DNS lookup for its service discovery.
NAPTR [RFC2915] and SRV [RFC2782] DNS resource records are
appropriate to provide service discovery mechanisms. The concrete
application of these resource records depends on the final ALTO
requests/response protocol. The use of NAPTR or SRV records is a
trade-off between flexibility and simplicity. S-NAPTR [RFC3958] and
U-NAPTR [RFC4848] mechanisms provide a Dynamic Delegation Discovery
System (DDDS) Application to map domain name, service name and
protocol name to a target host and port or to a target URI. SRV
records provide a mechanism to map domain name, service name and
transport protocol name to a target host and port. The use of a
NAPTR or SRV solution is open to discussion and depends on the
requirements of the ALTO protocol. Next section will asume the use
use of SRV records in the next sections are based on SRV.
5.1.1. DNS-based ALTO discovery
Figure 6. shows a general DNS ALTO server discovery mechanism. A
server must register its SRV resource record with a well known
service name (e.g. _ALTO._TCP.example.com) in the DNS system. The
service name in this document refers to the name used for DNS SRV
query, which includes the service label, protocol name (TCP or UDP)
and domain name. Any ALTO client that wants to get the IP address
and port of the ALTO server sends a DNS SRV query to the DNS server
in that domain .
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+-------------------------------------+
| DNS |
+-------------------------------------+
^ ^
| |
| |
|DNS configuration |DNS queries
|or dynamic update |and responses
| |
v v
+-------------+ +-------------+
| | | ALTO |
| ALTO Server | | Discovery |
| | | Client |
+-------------+ +-------------+
Figure 6: DNS query for well known ALTO servers
5.1.2. Determine Service Name of Local ALTO servers
An ALTO discovery client must know its ALTO service name for it
before sending a query to the DNS system. Some ALTO servers may
provide service to the overall network, they may have well-known
service name. But in most cases, one ALTO server will only provide
service to its own local access network or autonomous system. There
will be multiple ALTO servers in the overall network. An ALTO
discovery client needs to find the service name of its local ALTO
server.
5.1.2.1. Using DHCP option for access domain name
There are DHCP options (OPTION_V4_ACCESS_DOMAIN and
OPTION_V6_ACCESS_DOMAIN) proposed in [I-D.ietf-geopriv-lis-discovery]
to discover the local access domain names. (Haibin: need to read the
new version of this draft, and update this section) The retrieved
access domain name can be used to form a SRV name by prefixing the
ALTO service label to the access domain name. If it failed with the
SRV lookup with this service name, then it will remove one tag from
the left hand of the access domain name and prefix the ALTO service
label to form a new SRV name. It will iterate the process until it
succeeds in getting an ATLO server information or failed.
It should be noticed that there are many residential gateways (RG)
which can act as DHCP servers themselves. RG becomes a hindrance
between the end terminals and the ALTO service provider's DHCP server
if we use DHCP. It should not depend on the update of all these RGs
to support this new DHCP Option for ALTO server discovery. A DHCP
Container Option [I-D.ietf-dhc-container-opt] for server
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configuration should be used here. With the Container Option, the
DHCP server for the consumer domain (e.g. RGs) can just pass the
server configuration to the end terminals without explicit knowledge
of the DHCP options contained in the Container. The DHCP Option for
the access domain name could be contained in the Container Option.
5.1.2.2. Use IANA Database
The service name of a client's local ALTO server could be formed by
adding the service and protocol label before its domain information.
IANA and its subsidiary organizations (e.g. APNIC) database can be
used to lookup the physical domain of a client through its public IP
address, i.e. which network operator and/or autonomous system the
client belongs to. The WHOIS service [WWW.WHOIS] on the Internet is
also available for this purpose. This mechanism requires ISPs assign
the domain names to their ALTO servers according to the AS and ISP
information (e.g. they have a rule to format the domain name,
AS.ISP.COM), then you can rebuid the domain name with the information
retrieved from WHOIS. Otherwise, you can't.
However, the mapping information may be changed due to the business
deals and network adjustment. For example, an ISP could sell some
part of its network (include all equipments, IP addresses, AS number,
and so on) to another ISP, and the ISP does not have the
responsibility to notify the IANA, and then the information in the
IANA database is wrong.
5.1.2.3. Reverse DNS lookup
BEP 22 [BEP-22] framework uses reverse DNS lookup to determine the
domain name of a client through its public address. And then use
service label and the domain name to lookup the local server in DNS.
The following limitations should be considered when use this
mechanism.
(1) This method assumes that the access network provider also
provides the reverse DNS record and they control the domain that is
indicated in the "PTR" record. (In most cases it is true, but not
always)
(2) Furthermore, this method might not apply where a host is given a
domain name that is different from the domain name of the access
network.
(3) In case of NAT and a public ALTO server, it requires the ALTO
client to know its public IP address.
The advantage is that it doesn't require any update/configuration/
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change in the DHCP servers of any residential gateway.
5.2. DHCP
There are other ways using DHCP to locate an ALTO server. One
suggestion is to use DHCP to obtain the ALTO server IP address and
port information directly. New DHCP options are needed for this
purpose. The residential gateways consideration for DHCP option must
be considered as described in . (Section 5.1.2.1)
With this mechanism, the DHCP server needs to support load balance if
there are more than one ALTO servers for this access domain. The
maintenance is costly when the address of ALTO server changes.
5.3. XRD
XRD is described in [XEP-1.0]. In order to begin the XRD discovery
you need the URL (or XRI) of the resource you want to discover links/
services related to. In other XRD use cases like OpenId or
OpenSocial, it is clear that you know that URL (the OpenId url of the
user, or the url of the OS container). But in case of ALTO Server
Discovery, the obtainment of this initial URL also needs to use some
discovery framework.
5.4. Provisioning
A network operator can simply provide a configuration file that
contains the ALTO server address for its clients, provided that there
are only one or a few ALTO servers which provide identical service
for its network. An application can also provide such a
configuration file containing the ALTO server address if an existing
ALTO server provides identical service to the overall network.
5.5. Manual Configuration
Manual configuration of the ALTO service location(s) could work in a
single ISP network scope, but is not scalable when multiple ISPs or
cross-domain ALTO services are required. P2P applications often
connect peers from ISPs that they may not have contacted before, and
manual configuration will not work without any prior knowledge of the
ALTO servers.
5.6. Multicast and broadcast
Multicast or broadcast MAY be used in some scenarios for ALTO
discovery.
IP-multicast-based discovery generally works in two ways:
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1. Clients send out multicast discovery requests and listen for
responses (usually unicast) from available servers or service
providers.
2. Servers or service providers send out multicast announcements
when they become available or periodically, and clients waits for the
next available multicast announcement to identify the servers or
service providers.
The on-demand requests and periodic announcements are not mutually
exclusive. An implementation can choose to utilize both
simultaneously. The configuration effort of multicast discovery is
fairly straightforward, only the multicast address and port are
needed. Service types and additional information are often encoded
in the requests or announcements messages, enabling the same
multicast channel to support discovery of different resources or
services. There are two main constraints of multicast-based
discovery - scopes and flooding messages. Routers disable multicast
forwarding by default, making it practically a single-subnet
solution. Some forms of discovery proxies are needed to extend the
scope of multicast discovery to multiple subnets. The second issue
is the flooding of multicast messages to all hosts on the same
subnet. The total bandwidth consumed by multicast depends on the
arrival rate the client application requests, and/or the frequency of
the service announcements. Older generations of 802.11-based
wireless access points often slow down the transmission of multicast
messages or generally have a higher packet loss rate for those,
causing some multicast discovery implementation to automatically re-
send multicast requests or announcements by default. This mitigation
further increases the amount of flooding messages on the LAN.
Examples of multicast-based discovery include [I-D.cheshire-dnsext-
multicastdns], [I-D.cai-ssdp-v1], [WSD], SLP [RFC2165], and LLMNR
[RFC4795].
5.7. Caching
Once a client has located an ALTO server for the first time, it can
cache it for use as future ALTO server. There are implications in
case of mobility of devices.
6. Security Considerations
As this document mainly proposes to use DNS and DHCP for ALTO service
discovery, it will depend on the DHCP security and DNS security for
this service discovery.
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7. IANA Considerations
The service label for the ALTO service will depend on the final
protocol name for application-layer traffic optimization(TBD).
8. Acknowledgements
The authors would like to give special thanks to Roni Even for his
continuous contribution to this document.
We would also like to thank the following experts for their review
and valuable comments.
Y. Richard Yang
Xingfeng Jiang
Jay Gu
Ning Zong
(To be added)
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
specifying the location of services (DNS SRV)", RFC 2782,
February 2000.
[RFC3958] Daigle, L. and A. Newton, "Domain-Based Application
Service Location Using SRV RRs and the Dynamic Delegation
Discovery Service (DDDS)", RFC 3958, January 2005.
[RFC4848] Daigle, L., "Domain-Based Application Service Location
Using URIs and the Dynamic Delegation Discovery Service
(DDDS)", RFC 4848, April 2007.
[RFC2915] Mealling, M. and R. Daniel, "The Naming Authority Pointer
(NAPTR) DNS Resource Record", RFC 2915, September 2000.
[I-D.ietf-alto-problem-statement]
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Seedorf, J. and E. Burger, "Application-Layer Traffic
Optimization (ALTO) Problem Statement",
draft-ietf-alto-problem-statement-04 (work in progress),
September 2009.
[I-D.ietf-geopriv-lis-discovery]
Thomson, M. and J. Winterbottom, "Discovering the Local
Location Information Server (LIS)",
draft-ietf-geopriv-lis-discovery-15 (work in progress),
March 2010.
[I-D.ietf-dhc-container-opt]
Droms, R., "Container Option for Server Configuration",
draft-ietf-dhc-container-opt-05 (work in progress),
March 2009.
9.2. Informative References
[RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
June 1999.
[RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC
Text on Security Considerations", BCP 72, RFC 3552,
July 2003.
[RFC2165] Veizades, J., Guttman, E., Perkins, C., and S. Kaplan,
"Service Location Protocol", RFC 2165, June 1997.
[RFC4795] Aboba, B., Thaler, D., and L. Esibov, "Link-local
Multicast Name Resolution (LLMNR)", RFC 4795,
January 2007.
[I-D.kiesel-alto-3pdisc]
Kiesel, S., Tomsu, M., Schwan, N., and M. Scharf, "Third-
party ALTO server discovery", draft-kiesel-alto-3pdisc-02
(work in progress), March 2010.
[I-D.cheshire-dnsext-multicastdns]
Cheshire, S. and M. Krochmal, "Multicast DNS",
draft-cheshire-dnsext-multicastdns-11 (work in progress),
March 2010.
[I-D.wang-alto-p4p-specification]
Wang, Y., Alimi, R., Pasko, D., Popkin, L., and Y. Yang,
"P4P Protocol Specification",
draft-wang-alto-p4p-specification-00 (work in progress),
March 2009.
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[I-D.narten-iana-considerations-rfc2434bis]
Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs",
draft-narten-iana-considerations-rfc2434bis-09 (work in
progress), March 2008.
[I-D.cai-ssdp-v1]
Goland, Y., Cai, T., Leach, P., Gu, Y., and S. Albright,
"Simple Service Discovery Protocol/1.0 Operating without
an Arbiter", October 1999, <draft-cai-ssdp-v1-03>.
[WWW.WHOIS]
"http://www.whois.net".
[BEP-22] Harrison, D., Shalunov, S., and G. Hazel, "BitTorrent
Local Tracker Discovery Protocol", October 2008,
<http://bittorrent.org/beps/bep_0022.html>.
[XEP-1.0] Hammer-Lahav, E., "Extensible Resource Descriptor (XRD)
Version 1.0", May 2009, <http://www.oasis-open.org/
committees/download.php/32686/xrd-1.0-wd01.html>.
[WSD] Beatty, J., "Web Services Dynamic Discovery (WS-
Discovery)", April 2005, <http://specs.xmlsoap.org/ws/
2005/04/discovery/ws-discovery.pdf>.
Authors' Addresses
Song Haibin
Huawei
Email: melodysong@huawei.com
Marco Tomsu
Alcatel-lucent Bell Labs
Lorenzstrasse 10
70435 Stuttgart
Germany
Email: marco.tomsu@alcatel-lucent.com
URI: www.alcatel-lucent.com/bell-labs
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Gustavo Garcia
Telefonica I+D
Emilio Vargas
Madrid, Madrid
Spain
Phone: +34 913129826
Email: ggb@tid.es
Yu-Shun Wang
Microsoft Corp.
One Microsoft Way
Redmond, WA 98052
USA
Email: yu-shun.wang@microsoft.com
Victor Pascual
Tekelec
Am Borsigturm 11
Berlin D-13507
Germany
Phone: +49 30 32 51 32 12
Email: victor@iptel.org
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