draft-ietf-rserpool-arch-06.txt   draft-ietf-rserpool-arch-07.txt 
Network Working Group M. Tuexen, Ed. Network Working Group M. Tuexen, Ed.
Internet-Draft Univ. of Applied Sciences Muenster Internet-Draft Univ. of Applied Sciences Muenster
Expires: December 28, 2003 Q. Xie Expires: April 11, 2004 Q. Xie
Motorola, Inc. Motorola, Inc.
R. Stewart R. Stewart
M. Shore M. Shore
Cisco Systems, Inc. Cisco Systems, Inc.
L. Ong
Ciena Corporation
J. Loughney J. Loughney
Nokia Research Center Nokia Research Center
M. Stillman October 12, 2003
Nokia
June 29, 2003
Architecture for Reliable Server Pooling Architecture for Reliable Server Pooling
draft-ietf-rserpool-arch-06.txt draft-ietf-rserpool-arch-07.txt
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that other Task Force (IETF), its areas, and its working groups. Note that other
groups may also distribute working documents as Internet-Drafts. groups may also distribute working documents as Internet-Drafts.
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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."
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www.ietf.org/ietf/1id-abstracts.txt. www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
This Internet-Draft will expire on December 28, 2003. This Internet-Draft will expire on April 11, 2004.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved. Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract Abstract
This document describes an architecture and protocols for the This document describes an architecture and protocols for the
management and operation of server pools supporting highly reliable management and operation of server pools supporting highly reliable
applications, and for client access mechanisms to a server pool. applications, and for client access mechanisms to a server pool.
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2.2.1 Endpoint Name Resolution Protocol . . . . . . . . . . . . . 5 2.2.1 Endpoint Name Resolution Protocol . . . . . . . . . . . . . 5
2.2.2 Aggregate Server Access Protocol . . . . . . . . . . . . . . 6 2.2.2 Aggregate Server Access Protocol . . . . . . . . . . . . . . 6
2.2.3 PU <-> NS Communication . . . . . . . . . . . . . . . . . . 6 2.2.3 PU <-> NS Communication . . . . . . . . . . . . . . . . . . 6
2.2.4 PE <-> NS Communication . . . . . . . . . . . . . . . . . . 7 2.2.4 PE <-> NS Communication . . . . . . . . . . . . . . . . . . 7
2.2.5 PU <-> PE Communication . . . . . . . . . . . . . . . . . . 7 2.2.5 PU <-> PE Communication . . . . . . . . . . . . . . . . . . 7
2.2.6 NS <-> NS Communication . . . . . . . . . . . . . . . . . . 8 2.2.6 NS <-> NS Communication . . . . . . . . . . . . . . . . . . 8
2.2.7 PE <-> PE Communication . . . . . . . . . . . . . . . . . . 9 2.2.7 PE <-> PE Communication . . . . . . . . . . . . . . . . . . 9
2.3 Failover Support . . . . . . . . . . . . . . . . . . . . . . 9 2.3 Failover Support . . . . . . . . . . . . . . . . . . . . . . 9
2.3.1 Business Cards . . . . . . . . . . . . . . . . . . . . . . . 9 2.3.1 Business Cards . . . . . . . . . . . . . . . . . . . . . . . 9
2.3.2 Cookies . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2.3.2 Cookies . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.4 Typical Interactions between RSerPool Components . . . . . . 10 2.4 Typical Interactions between RSerPool Components . . . . . . 11
3. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 12 3. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.1 Two File Transfer Examples . . . . . . . . . . . . . . . . . 12 3.1 Two File Transfer Examples . . . . . . . . . . . . . . . . . 12
3.1.1 The RSerPool Aware Client . . . . . . . . . . . . . . . . . 13 3.1.1 The RSerPool Aware Client . . . . . . . . . . . . . . . . . 13
3.1.2 The RSerPool Unaware Client . . . . . . . . . . . . . . . . 14 3.1.2 The RSerPool Unaware Client . . . . . . . . . . . . . . . . 14
3.2 Telephony Signaling Example . . . . . . . . . . . . . . . . 15 3.2 Telephony Signaling Example . . . . . . . . . . . . . . . . 15
3.2.1 Decomposed GWC and GK Scenario . . . . . . . . . . . . . . . 15 3.2.1 Decomposed GWC and GK Scenario . . . . . . . . . . . . . . . 15
3.2.2 Collocated GWC and GK Scenario . . . . . . . . . . . . . . . 17 3.2.2 Collocated GWC and GK Scenario . . . . . . . . . . . . . . . 17
4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 18 4. Security Considerations . . . . . . . . . . . . . . . . . . 18
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 18
Normative References . . . . . . . . . . . . . . . . . . . . 18 Normative References . . . . . . . . . . . . . . . . . . . . 18
Informative References . . . . . . . . . . . . . . . . . . . 18 Informative References . . . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 19 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 19
Intellectual Property and Copyright Statements . . . . . . . 21 Intellectual Property and Copyright Statements . . . . . . . 21
1. Introduction 1. Introduction
1.1 Overview 1.1 Overview
This document defines an architecture, for providinge a highly This document defines an architecture, for providing a highly
available reliable server function in support of some service. The available reliable server function in support of a service or set of
way this is achieved is by forming a pool of servers, each of which services. This is achieved is by forming a pool of servers, each of
is capable of supporting the desired service, and providing a name which is capable of supporting the desired service(s), and providing
service that will resolve requests from a service user to the a name service that will resolve requests from a service user to the
identity of a working server in the pool. identity of a working server in the pool.
To access a server pool, the pool user consults a name server. The To access a server pool, the pool user consults a name server. The
name service itself can be provided by a pool of name servers using a name service itself can be provided by a pool of name servers using a
shared protocol to make the name resolution function fault-tolerant. shared protocol to make the name resolution function fault-tolerant.
It is assumed that the name space is kept flat and designed for a It is assumed that the name space is kept flat and designed for a
limited scale in order to keep the protocols simple, robust and fast. limited scale in order to keep the protocols simple, robust and fast.
The server pool itself is supported by a shared protocol between The server pool itself is supported by a shared protocol between
servers and the name service allowing servers to enter and exit the servers and the name service allowing servers to enter and exit the
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o Name Servers (NSs). o Name Servers (NSs).
o Pool Users (PUs). o Pool Users (PUs).
A server pool is defined as a set of one or more servers providing A server pool is defined as a set of one or more servers providing
the same application functionality. These servers are called Pool the same application functionality. These servers are called Pool
Elements (PEs). PEs form the first class of entities in the RSerPool Elements (PEs). PEs form the first class of entities in the RSerPool
architecture. Multiple PEs in a server pool can be used to provide architecture. Multiple PEs in a server pool can be used to provide
fault tolerance or load sharing, for example. fault tolerance or load sharing, for example.
Each server pool will be identifiable by a unique name which is Each server pool is identified by a unique name which is simply a
simply a byte string, called the pool handle. This allows binary byte string, called the pool handle. This allows binary names to be
names to be used. used.
These names are not valid in the whole internet but only in smaller These names are not valid in the whole internet but only in smaller
domains, called the operational scope. Furthermore, the namespace is domains, called the operational scope. Furthermore, the namespace is
assumed to be flat, so that multiple levels of query are not assumed to be flat, so that multiple levels of query are not
necessary to resolve a name request. necessary to resolve a name request.
The second class of entities in the RSerPool architecture is the The second class of entities in the RSerPool architecture is the
class of name servers (NSs). These name servers can resolve a pool class of name servers (NSs). These name servers can resolve a pool
handle to a list of information which allows the PU to access a PE of handle to a list of information which allows the PU to access a PE of
the server pool identified by the handle. This information includes: the server pool identified by the handle. This information includes:
o A list of IPv4 and/or IPv6 addresses. o A list of IPv4 and/or IPv6 addresses.
o A protocol field of the IP header specifying the transport layer o A protocol field specifying the transport layer protocol.
protocol or protocols.
o A port number associatiated with the transport protocol, e.g. o A port number associated with the transport protocol, e.g. SCTP,
SCTP, TCP or UDP. TCP or UDP.
Please note that the RSerPool architecture supports both IPv4 and Note that the RSerPool architecture supports both IPv4 and IPv6
IPv6 addressing. A PE can also support multiple transport layers. addressing.
In each operational scope there must be at least one name server. All In each operational scope there must be at least one name server. All
name servers within the operational scope have knowledge of all name servers within the operational scope have knowledge of all
server pools within the operational scope. server pools within the operational scope.
A third class of entities in the architecture is the Pool User (PU) A third class of entities in the architecture is the Pool User (PU)
class, consisting of the clients being served by the PEs of a server class, consisting of the clients being served by the PEs of a server
pool. pool.
2.2 RSerPool Protocol Overview 2.2 RSerPool Protocol Overview
The RSerPool requested features can be obtained with the help of the The RSerPool requested features can be obtained with the help of the
combination of two protocols: ENRP (Endpoint Name Resolution combination of two protocols: ENRP (Endpoint Name Resolution
Protocol) and ASAP (Aggregate Server Access Protocol). Protocol) and ASAP (Aggregate Server Access Protocol).
2.2.1 Endpoint Name Resolution Protocol 2.2.1 Endpoint Name Resolution Protocol
The name servers use a protocol called Endpoint Name Resolution The name servers use a protocol called Endpoint Name Resolution
Protocol (ENRP) for communication with each other to make sure that Protocol (ENRP) for communication with each other to exchange
all have the same information about the server pools. information and updates about the server pools.
ENRP is designed to provide a fully distributed fault-tolerant ENRP is designed to provide a fully distributed fault-tolerant
real-time translation service that maps a name to a set of transport real-time translation service that maps a name to a set of transport
addresses pointing to a specific group of networked communication addresses pointing to a specific group of networked communication
endpoints registered under that name. ENRP employs a client-server endpoints registered under that name. ENRP employs a client-server
model with which an name server will respond to the name translation model in which a name server will respond to the name translation
service requests from endpoint clients running on the same host or service requests from endpoint clients.
running on different hosts.
RFC3237 [7] also requires that the name servers should not resolve a RFC3237 [8] also requires that the name servers should not resolve a
pool handle to a transport layer address of a PE which is not in pool handle to a transport layer address of a PE which is not in
operation. Therefore each PE is supervised by one specific name operation. Therefore each PE is supervised by one specific name
server, called the home NS of that PE. If it detects that the PE is server, called the home NS of that PE. If it detects that the PE is
out of service all other name servers are informed by using ENRP. out of service all other name servers are informed by using ENRP.
2.2.2 Aggregate Server Access Protocol 2.2.2 Aggregate Server Access Protocol
The PU wanting service from the pool uses the Aggregate Server Access The PU wanting service from the pool uses the Aggregate Server Access
Protocol (ASAP) to access members of the pool. Depending on the Protocol (ASAP) to access members of the pool. Depending on the
level of support desired by the application, use of ASAP may be level of support desired by the application, use of ASAP may be
limited to an initial query for an active PE, or ASAP may be used to limited to an initial query for an active PE, or ASAP may be used to
mediate all communication between the PU and PE, so that automatic mediate all communication between the PU and PE, so that automatic
failover from a failed PE to an alternate PE can be supported. failover from a failed PE to an alternate PE can be supported.
ASAP in conjunction with ENRP provides a fault tolerant data transfer ASAP uses a name-based addressing model which isolates a logical
mechanism over IP networks. ASAP uses a name-based addressing model communication endpoint from its IP address(es), thus effectively
which isolates a logical communication endpoint from its IP eliminating the binding between the communication endpoint and its
address(es), thus effectively eliminating the binding between the physical IP address(es) which normally constitutes a single point of
communication endpoint and its physical IP address(es) which normally failure.
constitutes a single point of failure.
In addition, ASAP defines each logical communication destination as a In addition, ASAP provides some mechanisms to support loadsharing
server pool, providing full transparent support for server-pooling between PEs within the same pool and to support the upper layer in
and load sharing. case of a failover between PEs becomes necessary.
ASAP is also used by a server to join or leave a server pool. It ASAP is also used by a PE to join or leave a server pool. It
registers or deregisters itself by communicating with a name server, registers or deregisters itself by communicating with a name server,
which will normally the home NS. ASAP allows dynamic system which will normally the home NS. ASAP allows dynamic system
scalability, allowing the pool membership to change at any time scalability, allowing the pool membership to change at any time.
without interruption of the service.
2.2.3 PU <-> NS Communication 2.2.3 PU <-> NS Communication
The PU <-> NS communication is used for doing name queries. The PU The PU <-> NS communication is used for performing name queries. The
sends a pool handle to the NS and gets back the information necessary PU sends a pool handle to the NS and gets back the information
for accessing a server in a server pool. necessary for accessing a server in a server pool.
This communication can be based on SCTP or TCP if the PU does not
support SCTP. The protocol stack for an SCTP capable PU is given in
Figure 1.
******** ******** ******** ********
* PU * * NS * * PU * * NS *
******** ******** ******** ********
+------+ +------+ +------+ +------+
| ASAP | | ASAP | | ASAP | | ASAP |
+------+ +------+ +------+ +------+
| SCTP | | SCTP | | SCTP | | SCTP |
+------+ +------+ +------+ +------+
| IP | | IP | | IP | | IP |
+------+ +------+ +------+ +------+
Protocol stack between PU and NS Protocol stack between PU and NS
Figure 1 Figure 1
This communication can be based on SCTP or TCP if the PU does not
support SCTP. The protocol stack for an SCTP capable PU is given in
Figure 1.
2.2.4 PE <-> NS Communication 2.2.4 PE <-> NS Communication
The PE <-> NS communication is used for registration and The PE <-> NS communication is used for registration and
deregistration of the PE in one ore more pools and for the deregistration of the PE in one or more pools and for the supervision
supervision of the PE by the home NS. This communication is based on of the PE by the home NS. This communication is based on SCTP, the
SCTP, the protocol stack is shown in the following figure. protocol stack is shown in the following figure.
******** ******** ******** ********
* PE * * NS * * PE * * NS *
******** ******** ******** ********
+------+ +------+ +------+ +------+
| ASAP | | ASAP | | ASAP | | ASAP |
+------+ +------+ +------+ +------+
| SCTP | | SCTP | | SCTP | | SCTP |
+------+ +------+ +------+ +------+
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Figure 2 Figure 2
2.2.5 PU <-> PE Communication 2.2.5 PU <-> PE Communication
The PU <-> PE communication can be divided into two parts: The PU <-> PE communication can be divided into two parts:
o control channel o control channel
o data channel o data channel
The data channel is used for the transmission of the upper layer The data channel is used for the transmission of the upper layer
data, the control channel is used to exchange RSerPool information. data, the control channel is used to exchange RSerPool information.
There are two supported scenarios: There are two supported scenarios:
o Multiplexed data and control channel. Both channels are o Multiplexed data and control channel. Both channels are
transported over one transport connection. This can either be an transported over one transport connection. This can either be an
SCTP association, with data and control channel are seperated by SCTP association, with data and control channel are separated by
the PPID, or an TCP connection, with data and control channel the PPID, or an TCP connection, with data and control channel
being handled by a TCP mapping layer. being handled by a TCP mapping layer.
o Data channel and no control channel. There is no restriction on o Data channel and no control channel. There is no restriction on
the transport protocol in this case. Note that certain enhanced the transport protocol in this case. Note that certain enhanced
failover services (e.g. business cards, state cookies, message failover services (e.g. business cards, state cookies, message
failover) are not available when this method is used. failover) are not available when this method is used.
For a given pool, all PUs and PEs should make the same choice for the For a given pool, all PUs and PEs should make the same choice for the
style of interaction between each other: that is, for a given pool, style of interaction between each other: that is, for a given pool,
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last cookie and send it to the new PE in case of a failover. last cookie and send it to the new PE in case of a failover.
See Section 2.3 for further details. See Section 2.3 for further details.
2.2.6 NS <-> NS Communication 2.2.6 NS <-> NS Communication
The communication between name servers is used to share the knowledge The communication between name servers is used to share the knowledge
about all server pools between all name servers in an operational about all server pools between all name servers in an operational
scope. scope.
For this communication ENRP over SCTP is used and the protocol stack
is shown in Figure 3.
******** ******** ******** ********
* NS * * NS * * NS * * NS *
******** ******** ******** ********
+------+ +------+ +------+ +------+
| ENRP | | ENRP | | ENRP | | ENRP |
+------+ +------+ +------+ +------+
| SCTP | | SCTP | | SCTP | | SCTP |
+------+ +------+ +------+ +------+
| IP | | IP | | IP | | IP |
+------+ +------+ +------+ +------+
Protocol stack between NS and NS Protocol stack between NS and NS
Figure 3
For this communication ENRP over SCTP is used. Figure 3
When a name server boots up a UDP multicast message may be sent out When a name initializes a UDP multicast message may be transmitted
for initial detection of other name servers in the operational scope. for initial detection of other name servers in the operational scope.
The other name servers send an answer using a unicast UDP message. The other name servers send a response using a unicast UDP message.
2.2.7 PE <-> PE Communication 2.2.7 PE <-> PE Communication
This is a special case of the PU <-> PE communication. In this case This is a special case of the PU <-> PE communication. In this case
the PU is also a PE in a server pool. the PU is also a PE in a server pool.
There is one additional point here: The PE acting as a PU can send There is one additional point here: The PE acting as a PU can send
the PE the information that it is acually a PE of pool. This means the PE the information that it is actually a PE of a pool. This means
that the pool handle is transferred via the control channel. See that the pool handle is transferred via the control channel. See
Section 2.3 for further details. Section 2.3 for further details.
2.3 Failover Support 2.3 Failover Support
If the PU detects the failure of a PE it may fail over to a different If the PU detects the failure of a PE it may fail over to a different
PE. The selection to a new PE should be made such that most likely PE. The selection to a new PE should be made such that most likely
the new PE is not affected by the failed one. the new PE is not affected by the failed one.
There are some mechanisms provided by RSerPool to support the There are some mechanisms provided by RSerPool to support the
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2.3.1 Business Cards 2.3.1 Business Cards
A PE can send a business card to its peer containing its pool handle A PE can send a business card to its peer containing its pool handle
and optionally information to which other PEs the peer should and optionally information to which other PEs the peer should
failover. failover.
Presenting the pool handle is important in case of PE <-> PE Presenting the pool handle is important in case of PE <-> PE
communication in which one of the PEs acts as a PU for establishing communication in which one of the PEs acts as a PU for establishing
the communication. The pool handle of the PE which initiated the the communication. The pool handle of the PE which initiated the
communication may not be know by the peer. communication may not be known by the peer.
Providing information to which PE the OU should failover can also be Providing information to which PE the PU should failover can also be
very important. Consider the scenario given in the following figure. very important. Consider the scenario presented in the following
figure.
....................... .......................
. +-------+ . . +-------+ .
. | | . . | | .
. | PE 1 | . . | PE 1 | .
. | | . . | | .
. +-------+ . . +-------+ .
. . . .
. Server Pool . . Server Pool .
. . . .
. . . .
+-------+ . +-------+ . +-------+ +-------+ . +-------+ . +-------+
| | . | | . | | | | . | | . | |
| PU 1 |------.------| PE 2 |------.-------| PU 2 | | PU 1 |------.------| PE 2 |------.-------| PU 2 |
| | . | | . | | | | . | | . | |
+-------+ . +-------+ . +-------+ +-------+ . +-------+ . +-------+
. . . .
. . . .
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. . . .
. . . .
. . . .
. . . .
. +-------+ . . +-------+ .
. | | . . | | .
. | PE 3 | . . | PE 3 | .
. | | . . | | .
. +-------+ . . +-------+ .
....................... .......................
Two PE accessing the same PE Two PUs accessing the same PE
Figure 4 Figure 4
PU 1 is using PE 2 of the server pool. Assume that PE 1 and PE 2 PU 1 is using PE 2 of the server pool. Assume that PE 1 and PE 2
share state but not PE 2 and PE 3. Using the business card of PE 2 it share state but not PE 2 and PE 3. Using the business card of PE 2 it
is possible for PE 2 to inform PU 1 that it should fail over to PE 1 is possible for PE 2 to inform PU 1 that it should fail over to PE 1
in case of a failure. in case of a failure.
A slightly more complicated situation is if two pool users, PU 1 and A slightly more complicated situation is if two pool users, PU 1 and
PU 2, use PE 2 but both, PU 1 and PU 2, need to use the same PE. Then PU 2, use PE 2 but both, PU 1 and PU 2, need to use the same PE. Then
it is important that PU 1 and PU 2 fail over to the same PE. This can it is important that PU 1 and PU 2 fail over to the same PE. This can
be handled in a way such that PE 2 gives the same business card to PU be handled in a way such that PE 2 gives the same business card to PU
1 and PU 2. 1 and PU 2.
2.3.2 Cookies 2.3.2 Cookies
Cookies may be sent from the PE to the PU if the PE wants to do this. Cookies may optionally be sent from the PE to the PU. The PU only
The PU only stores the last received cookie. In case of a fail over stores the last received cookie. In case of fail over the PU sends
it sends this last received cookie to the new PE. This method this last received cookie to the new PE. This method provides a
provides a simple way of state sharing between the PEs. Please note simple way of state sharing between the PEs. Please note that the old
that the old PE should sign the cookie and the receiving PE should PE should sign the cookie and the receiving PE should verify the
verify the signature. For the PU, the cookie has no structure and is signature. For the PU, the cookie has no structure and is only stored
only stored and transmitted to the new PE. and transmitted to the new PE.
2.4 Typical Interactions between RSerPool Components 2.4 Typical Interactions between RSerPool Components
The following drawing shows the typical RSerPool components and their The following drawing shows the typical RSerPool components and their
possible interactions with each other: possible interactions with each other:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~ operation scope ~ ~ operation scope ~
~ ......................... ......................... ~ ~ ......................... ......................... ~
~ . Server Pool 1 . . Server Pool 2 . ~ ~ . Server Pool 1 . . Server Pool 2 . ~
skipping to change at page 12, line 25 skipping to change at page 12, line 34
operation, administration, and maintenance (OAM) functions. operation, administration, and maintenance (OAM) functions.
(f) Other Clients <-> Proxy/Gateway: standard protocols The proxy/ (f) Other Clients <-> Proxy/Gateway: standard protocols The proxy/
gateway enables clients ("other clients"), which are not RSerPool gateway enables clients ("other clients"), which are not RSerPool
aware, to access services provided by an RSerPool based server aware, to access services provided by an RSerPool based server
pool. It should be noted that these proxies/gateways may become a pool. It should be noted that these proxies/gateways may become a
single point of failure. single point of failure.
3. Examples 3. Examples
[Editors note] This section has not been updated. The examples will
be updated after the architecture has been finalized.
In this section the basic concepts of ENRP and ASAP will be In this section the basic concepts of ENRP and ASAP will be
described. First an RSerPool aware FTP server is considered. The described. First an RSerPool aware FTP server is considered. The
interaction with an RSerPool aware and an non-aware client is given. interaction with an RSerPool aware and an non-aware client is given.
Finally, a telephony example is considered. Finally, a telephony example is considered.
3.1 Two File Transfer Examples 3.1 Two File Transfer Examples
In this section we present two separate file transfer examples using In this section we present two separate file transfer examples using
ENRP and ASAP. We present two separate examples demonstrating an ENRP and ASAP. We present two separate examples demonstrating an
ENRP/ASAP aware client and a client that is using a Proxy or Gateway ENRP/ASAP aware client and a client that is using a Proxy or Gateway
to perform the file transfer. In this example we will use a FTP to perform the file transfer. In this example we will use a FTP
RFC959 [3] model with some modifications. The first example (the RFC959 [4] model with some modifications. The first example (the
RSerPool aware one) will modify FTP concepts so that the file RSerPool aware one) will modify FTP concepts so that the file
transfer takes place over SCTP. In the second example we will use TCP transfer takes place over SCTP. In the second example we will use TCP
between the unaware client and the Proxy. The Proxy itself will use between the unaware client and the Proxy. The Proxy itself will use
the modified FTP with RSerPool as illustrated in the first example. the modified FTP with RSerPool as illustrated in the first example.
Please note that in the example we do NOT follow FTP RFC959 [3] Please note that in the example we do NOT follow FTP RFC959 [4]
precisely but use FTP-like concepts and attempt to adhere to the precisely but use FTP-like concepts and attempt to adhere to the
basic FTP model. These examples use FTP for illustrative purposes, basic FTP model. These examples use FTP for illustrative purposes,
FTP was chosen since many of the basic concept are well known and FTP was chosen since many of the basic concept are well known and
should be familiar to readers. should be familiar to readers.
3.1.1 The RSerPool Aware Client 3.1.1 The RSerPool Aware Client
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~ operation scope ~ ~ operation scope ~
~ ......................... ~ ~ ......................... ~
skipping to change at page 14, line 20 skipping to change at page 14, line 25
pool "File Transfer Pool" and a report would also be made that pool "File Transfer Pool" and a report would also be made that
PE(1,B) is non-responsive (this would cause appropriate audits PE(1,B) is non-responsive (this would cause appropriate audits
that may remove PE(1,B) from the pool if the NS had not already that may remove PE(1,B) from the pool if the NS had not already
detected the failure) (using (a)). detected the failure) (using (a)).
3.1.2 The RSerPool Unaware Client 3.1.2 The RSerPool Unaware Client
In this example we investigate the use of a Proxy server assuming the In this example we investigate the use of a Proxy server assuming the
same set of scenario as illustrated above. same set of scenario as illustrated above.
In this example the steps will occur:
1. The FTP client and the Proxy/Gateway are using the TCP-based ftp
protocol. The client sends the login request to the proxy (using
(e)).
2. The proxy behaves like a client and performs the actions
described under (1), (2) and (3) of the above description (using
(a), (b) and (c)).
3. The ftp communication continues and will be translated by the
proxy into the RSerPool aware dialect. This interworking uses (f)
and (c).
Note that in this example high availability is maintained between the
Proxy and the server pool but a single point of failure exists
between the FTP client and the Proxy, i.e. the command TCP connection
and its one IP address it is using for commands.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~ operation scope ~ ~ operation scope ~
~ ......................... ~ ~ ......................... ~
~ . "File Transfer Pool" . ~ ~ . "File Transfer Pool" . ~
~ . +-------+ +-------+ . ~ ~ . +-------+ +-------+ . ~
~ . |PE(1,A)| |PE(1,C)| . ~ ~ . |PE(1,A)| |PE(1,C)| . ~
~ . +-------+ +-------+ . ~ ~ . +-------+ +-------+ . ~
~ . ^ ^ . ~ ~ . ^ ^ . ~
~ . +----------+ | . ~ ~ . +----------+ | . ~
~ . +-------+ | | . ~ ~ . +-------+ | | . ~
skipping to change at page 15, line 4 skipping to change at page 15, line 37
~ +---------------------------------+ | | | ~ ~ +---------------------------------+ | | | ~
~ | v | (a) ~ ~ | v | (a) ~
~ v v ~ ~ v v ~
~ ::::::::::::::::: (e)-> ***************** ~ ~ ::::::::::::::::: (e)-> ***************** ~
~ : FTP Client :<------------->* Proxy/Gateway * ~ ~ : FTP Client :<------------->* Proxy/Gateway * ~
~ ::::::::::::::::: (f) ***************** ~ ~ ::::::::::::::::: (f) ***************** ~
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Architecture for RserPool unaware client. Architecture for RserPool unaware client.
Figure 7 Figure 7
In this example the steps will occur:
1. The FTP client and the Proxy/Gateway are using the TCP-based ftp
protocol. The client sends the login request to the proxy (using
(e)).
2. The proxy behaves like a client and performs the actions
described under (1), (2) and (3) of the above description (using
(a), (b) and (c)).
3. The ftp communication continues and will be translated by the
proxy into the RSerPool aware dialect. This interworking uses (f)
and (c).
Note that in this example high availability is maintained between the
Proxy and the server pool but a single point of failure exists
between the FTP client and the Proxy, i.e. the command TCP connection
and its one IP address it is using for commands.
3.2 Telephony Signaling Example 3.2 Telephony Signaling Example
This example shows the use of ASAP/RSerPool to support server pooling This example shows the use of ASAP/RSerPool to support server pooling
for high availability of a telephony application such as a Voice over for high availability of a telephony application such as a Voice over
IP Gateway Controller (GWC) and Gatekeeper services (GK). IP Gateway Controller (GWC) and Gatekeeper services (GK).
In this example, we show two different scenarios of deploying these In this example, we show two different scenarios of deploying these
services using RSerPool in order to illustrate the flexibility of the services using RSerPool in order to illustrate the flexibility of the
RSerPool architecture. RSerPool architecture.
skipping to change at page 16, line 29 skipping to change at page 16, line 45
Figure 8 Figure 8
As shown in the previous figure, the following sequence takes place: As shown in the previous figure, the following sequence takes place:
1. the Signaling Gateway (SG) receives an incoming signaling message 1. the Signaling Gateway (SG) receives an incoming signaling message
to be forwarded to the GWC. SG(X)'s ASAP layer would send an ASAP to be forwarded to the GWC. SG(X)'s ASAP layer would send an ASAP
request to its "local" NS to request the list of pool elements request to its "local" NS to request the list of pool elements
(PE's) of GWC (using (a)). The key used for this query is the (PE's) of GWC (using (a)). The key used for this query is the
pool handle of the GWC. The ASAP layer queues the data to be sent pool handle of the GWC. The ASAP layer queues the data to be sent
in local buffers until the NS responds. to the GWC in local buffers until the NS responds.
2. the NS would return a list of the three PE's A, B and C to the 2. the NS would return a list of the three PE's A, B and C to the
ASAP layer in SG(X) together with information to be used for ASAP layer in SG(X) together with information to be used for
load-sharing traffic across the gateway controller pool (using load-sharing traffic across the gateway controller pool (using
(b)). (b)).
3. the ASAP layer in SG(X) will select one PE (e.g., PE(2,C)) and 3. the ASAP layer in SG(X) will select one PE (e.g., PE(2,C)) and
send the signaling message to it (using (c)). The selection is send the signaling message to it (using (c)). The selection is
based on the load sharing information of the gateway controller based on the load sharing information of the gateway controller
pool. pool.
skipping to change at page 17, line 28 skipping to change at page 17, line 43
able to correctly handle the call and reply to PE(2, C) and hence able to correctly handle the call and reply to PE(2, C) and hence
progress the call. progress the call.
3.2.2 Collocated GWC and GK Scenario 3.2.2 Collocated GWC and GK Scenario
In this scenario, the GWC and GK services are collocated (e.g., they In this scenario, the GWC and GK services are collocated (e.g., they
are implemented as a single process). In such a case, one can form a are implemented as a single process). In such a case, one can form a
pool that provides both GWC and GK services as shown in the figure pool that provides both GWC and GK services as shown in the figure
below. below.
The same sequence as described in 5.2.1 takes place, except that step
(4) now becomes internal to the PE(3,C) (again, we assume Server C is
selected by SG).
........................................ ........................................
. Gateway Controller/Gatekeeper Pool . . Gateway Controller/Gatekeeper Pool .
. +-------+ . . +-------+ .
. |PE(3,A)| . . |PE(3,A)| .
. +-------+ . . +-------+ .
. +-------+ . . +-------+ .
. |PE(3,C)|<---------------------------+ . |PE(3,C)|<---------------------------+
. +-------+ . | . +-------+ . |
. +-------+ ^ . | . +-------+ ^ . |
. |PE(3,B)| | . | . |PE(3,B)| | . |
skipping to change at page 18, line 4 skipping to change at page 18, line 30
(c)| (e)| (c)| (e)|
v v v v
+++++++++++++++ ********* ***************** +++++++++++++++ ********* *****************
+ NS + * SG(X) * * Media Gateway * + NS + * SG(X) * * Media Gateway *
+++++++++++++++ ********* ***************** +++++++++++++++ ********* *****************
^ ^ ^ ^
| | | |
| <-(a) | | <-(a) |
+-------------------+ +-------------------+
(b)-> (b)->
Deployment of Collocated GWC and GK. Deployment of Collocated GWC and GK.
Figure 9 Figure 9
The same sequence as described in 5.2.1 takes place, except that step 4. Security Considerations
(4) now becomes internal to the PE(3,C) (again, we assume Server C is
selected by SG).
4. Acknowledgements The RSerPool protocol must allow us to secure the RSerPool
infrastructure. There are security and privacy issues that relate to
the namespace, pool element registration and user queries of the
namespace. In [2] a complete threat analysis of RSerPool components
is presented.
5. Acknowledgements
The authors would like to thank Bernard Aboba, Phillip Conrad, Harrie The authors would like to thank Bernard Aboba, Phillip Conrad, Harrie
Hazewinkel, Matt Holdrege, Christopher Ross, Werner Vogels and many Hazewinkel, Matt Holdrege, Christopher Ross, Werner Vogels and many
others for their invaluable comments and suggestions. others for their invaluable comments and suggestions.
Normative References Normative References
[1] Bradner, S., "The Internet Standards Process -- Revision 3", BCP [1] Bradner, S., "The Internet Standards Process -- Revision 3", BCP
9, RFC 2026, October 1996. 9, RFC 2026, October 1996.
[2] Stillman, M., "Threats Introduced by Rserpool and Requirements
for Security in response to Threats",
draft-ietf-rserpool-threats-02 (work in progress), October 2003.
Informative References Informative References
[2] Postel, J., "Transmission Control Protocol", STD 7, RFC 793, [3] Postel, J., "Transmission Control Protocol", STD 7, RFC 793,
September 1981. September 1981.
[3] Postel, J. and J. Reynolds, "File Transfer Protocol", STD 9, RFC [4] Postel, J. and J. Reynolds, "File Transfer Protocol", STD 9, RFC
959, October 1985. 959, October 1985.
[4] Guttman, E., Perkins, C., Veizades, J. and M. Day, "Service [5] Guttman, E., Perkins, C., Veizades, J. and M. Day, "Service
Location Protocol, Version 2", RFC 2608, June 1999. Location Protocol, Version 2", RFC 2608, June 1999.
[5] Ong, L., Rytina, I., Garcia, M., Schwarzbauer, H., Coene, L., [6] Ong, L., Rytina, I., Garcia, M., Schwarzbauer, H., Coene, L.,
Lin, H., Juhasz, I., Holdrege, M. and C. Sharp, "Framework Lin, H., Juhasz, I., Holdrege, M. and C. Sharp, "Framework
Architecture for Signaling Transport", RFC 2719, October 1999. Architecture for Signaling Transport", RFC 2719, October 1999.
[6] Stewart, R., Xie, Q., Morneault, K., Sharp, C., Schwarzbauer, [7] Stewart, R., Xie, Q., Morneault, K., Sharp, C., Schwarzbauer,
H., Taylor, T., Rytina, I., Kalla, M., Zhang, L. and V. Paxson, H., Taylor, T., Rytina, I., Kalla, M., Zhang, L. and V. Paxson,
"Stream Control Transmission Protocol", RFC 2960, October 2000. "Stream Control Transmission Protocol", RFC 2960, October 2000.
[7] Tuexen, M., Xie, Q., Stewart, R., Shore, M., Ong, L., Loughney, [8] Tuexen, M., Xie, Q., Stewart, R., Shore, M., Ong, L., Loughney,
J. and M. Stillman, "Requirements for Reliable Server Pooling", J. and M. Stillman, "Requirements for Reliable Server Pooling",
RFC 3237, January 2002. RFC 3237, January 2002.
Authors' Addresses Authors' Addresses
Michael Tuexen (editor) Michael Tuexen (editor)
Univ. of Applied Sciences Muenster Univ. of Applied Sciences Muenster
Stegerwaldstr. 39 Stegerwaldstr. 39
48565 Steinfurt 48565 Steinfurt
Germany Germany
skipping to change at page 20, line 4 skipping to change at page 20, line 31
EMail: rrs@cisco.com EMail: rrs@cisco.com
Melinda Shore Melinda Shore
Cisco Systems, Inc. Cisco Systems, Inc.
809 Hayts Rd 809 Hayts Rd
Ithaca, NY 14850 Ithaca, NY 14850
USA USA
Phone: +1 607 272 7512 Phone: +1 607 272 7512
EMail: mshore@cisco.com EMail: mshore@cisco.com
Lyndon Ong
Ciena Corporation
10480 Ridgeview Drive
Cupertino, CA 95014
USA
EMail: lyong@ciena.com
John Loughney John Loughney
Nokia Research Center Nokia Research Center
PO Box 407 PO Box 407
FIN-00045 Nokia Group FIN-00045 FIN-00045 Nokia Group FIN-00045
Finland Finland
EMail: john.loughney@nokia.com EMail: john.loughney@nokia.com
Maureen Stillman
Nokia
127 W. State Street
Ithaca, NY 14850
USA
Phone: +1-607-273-0724
EMail: maureen.stillman@nokia.com
Intellectual Property Statement Intellectual Property Statement
The IETF takes no position regarding the validity or scope of any The IETF takes no position regarding the validity or scope of any
intellectual property or other rights that might be claimed to intellectual property or other rights that might be claimed to
pertain to the implementation or use of the technology described in pertain to the implementation or use of the technology described in
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might or might not be available; neither does it represent that it might or might not be available; neither does it represent that it
has made any effort to identify any such rights. Information on the has made any effort to identify any such rights. Information on the
IETF's procedures with respect to rights in standards-track and IETF's procedures with respect to rights in standards-track and
 End of changes. 

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