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Internet Engineering Task Force Eric S. Crawley
Internet-Draft Bay Networks, Inc.
draft-ietf-issll-lane-00.txt November 1996
Integrated Services over ATM LAN Emulation (LANE) Networks
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 ds.internic.net (US East Coast), nic.nordu.net (Europe),
ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific Rim).
Abstract
This document discusses the mapping of the Integrated Services
(IntServ) models to ATM Forum LAN Emulation version 2 (LANEv2)
networks. This involves the combination of three items: LANEv2, IEEE
802.1p, and mapping of IntServ models to ATM.
1. Introduction
As the name states, LANE [1-3] tries to emulate the behavior of IEEE
802 style networks but has access to the QoS facilities that ATM can
provide. Although these features are not used in LANEv1, LANEv2 is
expected to utilize them and have QoS capabilities. Given that IEEE
802.1 is developing class of service mechanisms for 802 networks, it
only makes sense to apply these to LANE and utilize some of the
mappings being defined for IntServ services over ATM to create QoS
capabilities that can meet the needs of IntServ and LANE.
2. LANE
The ATM Forum's LAN Emulation (LANE) standard is a simple way to use
ATM to connect network devices so they appear to each other as devices
on an IEEE 802-style network (e.g. Ethernet). It hides the mechanisms
of ATM from the layer 2 and higher protocols allowing for quick
adoption of ATM. LANE provides services for address resolution,
broadcast, and multicast so the LAN Emulation Client (LEC) behaves like
it would on a traditional multi-access LAN. LANEv2, currently under
development in the ATM Forum provides enhanced capabilities over LANEv1
including enhanced multicast support, server redundancy, and QoS.
LECs set up ATM Virtual Circuits (referred to as Data Direct VCs or
DDVCs) between each other in order to transfer data. VCs are set up in
response to LANE ARP Requests (LE_ARPs). When one LEC wants to
transmit data to another LEC, it LE_ARPs for the destination MAC
address. The LEC that services the requested MAC address responds and
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INTERNET DRAFT Integrated Services over LANE November 1996
sets up a DDVC back to the requesting LEC. MAC addresses are
maintained in the native format of the type of LAN being emulated.
3. IEEE 802.1p
IEEE has been adding a class of service capability in 802.1p [5] and
802.1Q [4]. There are three bits that specify the _User Priority_ for
a given frame. This yields 8 different service classes. The minimal
implementation of these services is a strict priority with larger
values getting a greater priority (0 = lowest, 7 = highest). It is
even possible to limit the number of queues by lumping multiple
priorities into the same queue. While this is the minimal
interpretation, it is also possible to assign specific behaviors to the
User Priorities. This document will discuss mapping specific IntServ
behaviors to particular priorities for 802.1p when applied to LANE.
[10] discusses the use of specific 802.1p priorities for particular
IntServ models. Some initial mappings are proposed and a mechanism
that allows an end system to request what priority to use for a
particular flow is discussed.
While [10] discusses many of the architectural and protocol
considerations for mapping user priorities, the basic mapping can be
fairly simple. The following is one such example taken from [10].
Priority Service
0 "less than" Best Effort
1 Best Effort
2 reserved
3 reserved
4 Controlled Load
5 reserved
6 Guaranteed Service
7 reserved
Notice that all the IntServ traffic is set to only two User Priorities.
While this may not be an optimal mapping, it is provided here as an
example. Further options divide the Guaranteed Service between
multiple priorities that might provide some specific delay bounds that
more closely match application needs.
4. Applying 802.1p to LANE
The application of IEEE 802.1p to LANE is described in [6]. The basic
scheme allows multiple Data Direct VCs to be set up between LECs for
each 802.1p User Priority. This means that a LEC can have up to 8
different DDVCs between it and any other LEC on the Emulated LAN
(ELAN). The call setup parameters for each type of VC can be set up by
an administrator and provided to the LEC from the LAN Emulation
Configuration Server (LECS). When the LEC transmits a packet, it
checks the User Priority and places on the DDVC that corresponds to the
priority. This means that all queue management is handled by ATM
traffic management, eliminating the need for a separate packet
scheduler in the LEC.
The remaining problem is to determine what call setup parameters should
be used for the DDVCs that carry traffic corresponding to the IntServ
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INTERNET DRAFT Integrated Services over LANE November 1996
Controlled Load [7] and Guaranteed Service [8] models. In the example
provided in section 3, these parameters would be used for the VCs for
priorities 4 and 6.
5. Integrated Services Mapping to ATM
[9] describes the mapping of the Controlled Load and Guaranteed Service
models to IETF IP over ATM networks. This provides a set of call setup
parameters that can be used for supporting the IntServ Controlled Load
and Guaranteed Service models. These call setup parameters can be
applied to the VCs that are set up by the LECs. This allows the LEC to
provide very specific support for IntServ flows as IEEE 802.1p
priorities on emulated LANs. [9] allows for multiple mappings from
IntServ to ATM based on the IntServ model and the ATM service
categories available. For example, Guaranteed Service can be mapped to
both Constant Bit Rate (CBR) and real time Variable Bit Rate (rtVBR)
service classes with appropriate call setup parameters for each. For
the VCs corresponding to the priorities and service models used, the
call setup parameters can be determined to provide the proper QoS
required by the service model.
6. The Missing Pieces
Since LECs will possibly be sending traffic for multiple flows over the
same DDVC, the sizing of the DDVC becomes an important management
problem. The DDVCs must be sized to accommodate all the traffic for a
particular class. For example, if a rtVBR VC with a Maximum Cell Rate
(MCR) that equates to a bandwidth of 10Mb/s, is created to carry all
the Controlled Load traffic from a given LEC, then the amount of
Controlled Load traffic cannot exceed 10Mb/s even though the LEC may
have a link to the ATM network that runs at a much higher rate.
Additionally, either the traffic sources must be well behaved or the VC
must be over-allocated to handle situations where multiple flows are
aggregated over the same priority. It should be noted that this does
solve some of the scaling problems for IntServ over ATM noted in [11]
and [12] by aggregating multiple flows over a single VC.
The setup parameters for the 802.1p traffic classes must be extracted
from [9] and added to the MIBs used by the LANE Configuration Server
with comments about which values should be administratively controlled
by the network administrator. This is reserved for a future revision
of this draft.
7. Security Considerations
Security issues are not discussed in this memo.
8. References
1. ATM Forum Technical Committee. LAN Emulation over ATM, Version 1.0
Specification, af-lane-0021.000, January 1995.
2. ATM Forum Technical Committee. LAN Emulation over ATM Version 2 -
LNNI Specification - Draft 7, BTD-LANE-LNNI-02.07, December 1996.
3. ATM Forum Technical Committee. LAN Emulation over ATM Version 2 -
LUNI Specification - Draft 5, BTD-LANE-LUNI-02.05, December 1996.
4. LAN MAN Standards Committee of the IEEE Computer Society. Draft
Standard for Virtual Bridged Local Area Networks, P802.1Q.
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INTERNET DRAFT Integrated Services over LANE November 1996
5. LAN MAN Standards Committee of the IEEE Computer Society. Draft
Standard for Traffic Class and Dynamic Multicast Filtering Services
in Bridged Local Area Networks (Draft Supplement to 802.1D),
P802.1p.
6. E. Crawley, J. Luciani, N. Finn. LANE QoS Using IEEE 802.1p Service
Classes, ATM Forum Contribution, AF-96-1632.
7. J. Wroclawski. Specification of the Controlled-Load Network Element
Service. Internet Draft, draft-ietf-intserv-ctrl-load-svc-03.txt,
August 1996.
8. S. Shenker, C. Partridge, R. Guerin. Specification of Guaranteed
Quality of Service. Internet Draft, draft-ietf-intserv-guaranteed-
svc-06.txt, June 1996.
9. M. Borden, M. Garrett. Interoperation of Controlled-Load and
Guaranteed Service with ATM, Internet Draft, draft-ietf-issll-atm-
mapping-00.txt, September, 1996.
10. M. Seaman, A. Smith, E. Crawley. Integrated Services over IEEE
802.1D/802.1p Networks. Internet Draft, draft-ietf-issll-802-00.txt.
11. L. Berger, S. Berson, IP Integrated Services with RSVP over ATM.
Internet Draft, draft-ietf-issll-atm-support-01.txt, September 24,
1996.
12. M. Borden, E. Crawley, B. Davie, S. Batsell. Integration of Real-
Time Services in an IP-ATM Network Architecture, RFC1821, August
1995.
9. Author's Address
Eric S. Crawley
Bay Networks, Inc.
3 Federal Street
Billerica, MA 01821
esc@baynetworks.com
+1-508-670-8888
E. Crawley Expires May 1997 Page 4