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Internet Draft Jim Boyle
Expiration: December 25, 1997 MCI
File: draft-ietf-rsvp-cidr-ext-01.txt
RSVP Extensions for CIDR Aggregated Data Flows
June 25, 1997
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
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.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet- Drafts
Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe),
munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or
ftp.isi.edu (US West Coast).
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Abstract
This document presents extensions to Version 1 of the Resource
Reservation Setup Protocol (RSVP). These extensions ameliorate RSVP
support of Large Scale Multicast Applications (LSMA) and Virtual
Private Networks (VPN). With these types of applications, several
hosts at any particular site are participating in a session.
Efficient RSVP use requires aggregation of their addresses into a
single entry for classification purposes. The extensions allow such
aggregation of state in a simple manner that requires no changes to
the base RSVP specification.
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Table of Contents
1 Introduction 4
2 Object Overview 5
2.1 Examples of Use 5
2.2 Special Considerations 6
3 Object Definition 8
3.1 SESSION Class 8
3.2 FILTER_SPEC Class 9
3.3 SENDER_TEMPLATE Class 9
4 Additional Processing Rules for CIDR Extensions 10
5 Security Considerations 11
6 References 11
7 Acknowledgments and Authors' Information 12
7.1 Acknowledgments 12
7.2 Authors' Information 12
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1 Introduction
Two of the main applications that have been focused on in development
of the Resource Reservation Protocol [RSVP] are mbone video tele-
conferencing (VTC) and point-to-multipoint media distribution.
Though an important set of applications, they are distinctive in that
they assume a small number of originators of data per geographic
vicinity. Other applications such as the simulation network
applications described in in the LSMA working group [LSMA] have
different architectures that includes multiple sites (i.e. LANs)
inter-communicating with several workstations per site originating
network traffic. For the case of LSMAs, RSVP can be used to protect
the simulation traffic over the WAN, which is desirable since the
multicast transport protocols currently used can not throttle
transmission or retransmit lost packets. The objects described in
the base RSVP specification do not meet the RSVP needs of LSMAs in an
efficient manner. Another example of an application where several
hosts from a sender site originate traffic is VPNs.
This document proposes new objects in the SESSION, SENDER_TEMPLATE
and FILTER_SPEC classes. These objects, termed CIDR extensions,
extend the base specification to meet the needs of applications with
several senders per site in an efficient manner. The objects allow
hosts within a classless inter-domain routing (CIDR) prefix [RFCCIDR]
to be grouped by RSVP as a single entry. With CIDR extensions, a
host at each site would send out a PATH message with CIDR SESSION and
SENDER_TEMPLATE with a Tspec that described the aggregate traffic the
site expected to generate. A host at each receiving site would send
back a fixed filter style RESV message containing CIDR SESSION and
FILTER_SPEC objects.
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2 Object Overview
2.1 Examples of Use
2.1.1 LSMA
Suppose you have 4 sites participating in a distributed simulation.
Each site has 50 hosts and each site is sending 250 kbs of traffic to
a multicast address. A single host at each site sends a PATH message
with CIDR SESSION and CIDR SENDER_TEMPLATE objects and base
specification Tspec object describing that the site expects to
generate 250 kbs of traffic to the specified multicast address.
Nomination of which host sends this message is outside the scope of
RSVP, the application must perform this function. When such a PATH
message is received, a single host per recipient site sends back a
RESV message to the sender host with a CIDR SESSION and CIDR
FILTER_SPEC matching the sender's objects, a base specification
flowspec and a fixed-filter reservation style. Such a reservation
might say "Reserve 250 kbs of controlled load service for traffic
from 192.1.1.1/24 to 224.5.6.1/32". Aggregating multicast groups
within a range would be useful, but this proves problematic due to
possibly divergent routing paths per individual groups. This problem
is discussed in greater detail in section 2.2.??.
In the above example, 9 inter-site reservations would be established
with each reservation expected to match its respective Tspec. With
traditional objects, as detailed in the base specification, use of
RSVP to protect the aforementioned scenario could result in excessive
message and classification processing, in the case of distinct
reservations. For shared reservations, over-subscription of the
reservation (250 kbs of traffic flowing through a 750 kbs
reservation) would result.
2.1.2 VPN
CIDR extensions provide a scalable manner in which to provide VPN
services with RSVP. As an alternate approach, one might choose to
use an IP in IP tunnel which has some advantages but also has the
disadvantage that it forces the packets to be encapsulated at the
tunnel-ingress router. Suppose two corporate site offices would like
to setup VPN service with a main office. A host at each site would
send a PATH message to the respective host at the other sites. This
PATH message would use CIDR SESSION and SENDER_TEMPLATE objects and
would contain a Tspec describing the traffic from the originating
site to the destination site. In response, a RESV message would be
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sent using CIDR SESSION and CIDR FILTER_SPEC objects. In the case
mentioned, there would be 3 RSVP reservations installed in the
network. Without using tunnels, the above could not be supported by
the base specification objects.
2.2 Special Considerations for CIDR Objects
2.2.1 Route assumptions
In order for CIDR objects to work, and be most effective, an
assumption must be made that the RSVP administrator is aware of non-
singular routes for the aggregated address space. For unicast CIDR
SESSION objects, for instance, the RSVP exchange is taking place
between two distinct IP addresses. This can fail to provide full
coverage of inter-site traffic if a subset of the addresses within
the CIDR SESSION is routed differently than the route over which the
RSVP state was installed. It is likely that such route divergence is
caused by circumstances that the possessor of the address range is
aware of (such as multi-homing).
2.2.2 CIDR SESSION objects and Multicast
The assumption listed in Section 2.2.1 are not valid with many
multicast routing protocols. Therefore, to establish PATH state for
all groups within a range, a PATH message must be sent to each
destination address. As these might take different routes through
the network, it is better to send a Tspec that specifically covers
traffic from a site to that particular group, obviating the need for
CIDR SESSION for multicast. Therefore, applications should use a CIDR
Prefix length of 32 for multicast destinations.
Multicast routing protocols are source sensitive, so one should note
that CIDR aggregation of sender state may fail the singular route
assumption. This is the case for multicast routing protocols that
can set up multiple routes for hosts within the same unicast route
entry. For instance, in PIM-SM [PIM-SM] one host's packets to a
multicast group could take a shortest path through route while
packets from another host on the same LAN route through the
rendezvous point.
2.2.3 Overlapping SESSION definitions
There is also an issue with how to handle establishment of SESSION
state where the range of destination addresses covered by the
Destination Address / CIDR prefix length overlaps with already
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established sessions. In addition to some additional rules described
in section 4, the basic requirement is that any one session's range
of addresses may not bisect another session's range. Said another
way, they may overlap and one may be a subset of another, but they
cannot partially overlap. This would allow RSVP use above and beyond
a base level VPN RSVP use.
For potentially ambiguous situations where a packet could be
classified as belonging to different reservations, a longest match on
session should be done with no over-flow of best-effort traffic to
other reservations. As an example:
Reservation Sender Session
A 1.2.3.1/16, 5.6.7.8/24
B 1.2.3.1/24, 5.6.7.8/16
A packet from 1.2.3.4 to 5.6.7.7 would be applied to reservation A.
This follows the lines of RSVP's receiver oriented nature.
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3 Object Definition
The FILTER_SPEC, SENDER_TEMPLATE and SESSION class objects below
contain a CIDR prefix field that specifies which hosts should be
treated identically to the specified address. For example, in the
CIDR FILTER_SPEC address, a source address of 199.1.1.1 with a CIDR
prefix length of 24 (199.1.1.1/24 shorthand) would apply to all
source addresses in the range of 199.1.1.0 to 199.1.1.255.
3.1 SESSION Class
SESSION Class = 1
o IPv4 CIDR SESSION object: Class = 1 C-Type = 5
+-------------+-------------+-------------+-------------+
| IPv4 DestAddress (4 bytes) |
+-------------+-------------+-------------+-------------+
| CIDR Length | /////////////////////////////////////// |
+-------------+-------------+-------------+-------------+
| Protocol Id | Flags | DstPort |
+-------------+-------------+-------------+-------------+
o IPv6 CIDR Session object: Class = 1 C-TYPE = 6
+-------------+-------------+-------------+-------------+
| |
+ +
| |
+ IPv6 DestAddress (16 bytes) +
| |
+ +
| |
+-------------+-------------+-------------+-------------+
| CIDR Length | /////////////////////////////////////// |
+-------------+-------------+-------------+-------------+
| Protocol Id | Flags | DstPort |
+-------------+-------------+-------------+-------------+
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3.2 FILTER_SPEC Class
FILTER_SPEC Class = 10
o IPv4 CIDR FILTER_SPEC object: Class = 10, C-Type = 6
+-------------+-------------+-------------+-------------+
| IPv4 SrcAddress (4 bytes) |
+-------------+-------------+-------------+-------------+
| CIDR Length | /////////// | SrcPort |
+-------------+-------------+-------------+-------------+
o IPv6 CIDR FILTER_SPEC object: Class = 10 C-Type = 7
+-------------+-------------+-------------+-------------+
| |
+ +
| |
+ IPv6 SrcAddress (16 bytes) +
| |
+ +
| |
+-------------+-------------+-------------+-------------+
| CIDR Length | /////////// | SrcPort |
+-------------+-------------+-------------+-------------+
3.3 SENDER_TEMPLATE Class
SENDER_TEMPLATE Class = 11
o IPv4 CIDR SENDER_TEMPLATE object: Class = 11, C-Type = 6
Definition same as IPv4 CIDR FILTER_SPEC object.
o IPv6 CIDR SENDER_TEMPLATE object: Class = 11, C-Type = 7
Definition same as IPv6 CIDR FILTER_SPEC object.
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4 Additional Processing Rules for CIDR Extension objects
If Session Protocol = 0, no non-zero protocol sessions for range of
Destination Addresses may exist. Alternatively, if Session
Protocol is non-zero, no zero protocol session for range of
Destination Addresses may exist.
PathErr Returned: xx1 Conflicting Destination Protocols
ResvErr Returned: xx1 Conflicting Destination Protocols
If Session Protocol = 0, Dst Port must also be 0.
PathErr Returned: xx2 Inappropriate Port for Protocol
ResvErr Returned: xx2 Inappropriate Port for Protocol
If Destination Port = 0 in SESSION, Source Port must also be 0.
Message discarded.
Err Logged: Conflicting Source Port
If a node that does not support CIDR extensions receives a CIDR
extension object, as per the base specification, it must return an
error.
PathErr Returned: 14 Unknown C-Type
ResvErr Returned: 14 Unknown C-Type
Session Destination Address Range boundaries must not bisect
Destination Address Ranges of already defined Sessions.
PathErr Returned: xx3 Conflicting Session Address Definition
ResvErr Returned: xx3 Conflicting Session Address Definition
CIDR prefixes must be within a valid range of 16 to 32 (for IPv4)
or 16 to 128 (for IPv6).
PathErr Returned: xx4 Malformed Session Address
PathErr Returned: 21.04 Malformed Tspec
ResvErr Returned: 21.03 Malformed flowspec
For explicit style reservation, CIDR FILTER_SPEC must exactly match
CIDR SENDER_TEMPLATE of session with installed sender state.
ResvErr Returned: 04 No Sender Information for this RESV
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RESV session must must exactly match installed sender state
established by PATH message.
ResvErr Returned: 03 No Path Information for this RESV
5 Security Considerations
RSVP with CIDR extensions is not less secure than base specification
RSVP. Security for both can be addressed by use of MD5
authentication described in [RSVPMD5]. Though under development,
RSVP's policy procedures might also be used to assure that non-
authorized state is not installed.
6 References
[HLARTI] J.O. Calvin, R. Weatherly, "An Introduction to the High
Level Architecture (HLA) Runtime Infrastructure (RTI)". 14th DIS
Workshop, September 1995, Orlando, FL.
http://www.dmso.mil/docslib/briefs/DIS/14DIS/hla.html
[IEEE1] IEEE 1278.1-1995, Standard for Distributed Interactive
Simulation - Application Protocols.
[IEEE2] IEEE 1278.2-1995, Standard for Distributed Interactive
Simulation - Communication services and Profiles.
[LSMA-SCENARIOS] S. Seidensticker, W.G. Smith, M. Myjak. "Scenarios
and Appropriate Protocols for Distributed Interactive Simulation",
Internet Draft, June 1996, <draft-ietf-lsma-scenarios-00.txt>.
[RFCCIDR] V. Fuller, et. al. "Classless Interdomain Routing (CIDR):
an Address Assignment and Aggregation Strategy", RFC1519.
[RSVP] B. Braden, et. al. "Resource Reservation Protocol (RSVP) -
Version 1 Functional Specification", Internet Draft, July 1996,
<draft-ietf-rsvp-spec-14.txt>.
[RSVPMD5] F. Baker, "RSVP Cryptographic Authentication", Internet
Draft, May 1997, <draft-ietf-rsvp-md5-03.txt>.
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7 Author Information and Acknowledgments
The author wishes to especially thank Fred Baker for his guidance on
this topic. Several members of the RSVP and LSMA mailing lists also
provided invaluable feedback.
Jim Boyle
MCI
2100 Reston Parkway
Reston, VA 20191
Phone: 703.715.7006
EMail: jboyle@mci.net
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