draft-ietf-manet-issues-01.txt   draft-ietf-manet-issues-02.txt 
Internet Draft S. Corson Internet Draft S. Corson
Expiration: September 1998 University of Maryland Expiration: April 1999 University of Maryland
File: draft-ietf-manet-issues-01.txt J. Macker File: draft-ietf-manet-issues-02.txt J. Macker
Naval Research Laboratory Naval Research Laboratory
March 1998 October 1998
Mobile Ad hoc Networking (MANET): Mobile Ad hoc Networking (MANET):
Routing Protocol Performance Issues and Evaluation Considerations Routing Protocol Performance Issues and Evaluation Considerations
Status of this Memo Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas, documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts. working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
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
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Distribution of this memo is unlimited. Distribution of this memo is unlimited.
Abstract Abstract
This memo first describes the characteristics of Mobile Ad hoc This memo first describes the characteristics of Mobile Ad hoc
Networks (MANETs), and their idiosyncrasies with respect to Networks (MANETs), and their idiosyncrasies with respect to
traditional, hardwired packet networks. It then discusses the effect traditional, hardwired packet networks. It then discusses the effect
these differences have on the design and evaluation of network these differences have on the design and evaluation of network
control protocols with an emphasis on routing performance evaluation control protocols with an emphasis on routing performance evaluation
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fabric. It is what *unifies* a set of wireless IP interfaces (each fabric. It is what *unifies* a set of wireless IP interfaces (each
with their own IP address) and identifies them as belonging to the with their own IP address) and identifies them as belonging to the
same mobile platform. This approach permits maximum flexibility in same mobile platform. This approach permits maximum flexibility in
address assignment, and does not require that all IP addresses address assignment, and does not require that all IP addresses
attached to a given router fall under a common CIDR prefix. Router attached to a given router fall under a common CIDR prefix. Router
IDs are used at the IP layer for routing computations. To enable IP IDs are used at the IP layer for routing computations. To enable IP
routing to hosts associated with the router, the subnet mask(s) routing to hosts associated with the router, the subnet mask(s)
(encompassing the hosts on the mobile platform) should be advertised (encompassing the hosts on the mobile platform) should be advertised
with the router ID to permit routing table construction. with the router ID to permit routing table construction.
6. MANET Routing Protocol Performance Issues 5.1. Interaction with Standard IP Routing
In the near term, it is currently envisioned that MANETs will
function as *stub* networks, meaning that all traffic carried by
MANET nodes must either be sourced or sinked within the MANET.
Because of bandwidth and possibly power constraints, MANETs are not
presently envisioned to function as *transit* networks carrying
traffic which enters and then leaves the MANET (although this
restriction may be removed by subsequent technology advances). This
substantially reduces the amount of route advertisement required for
interoperation with the existing fixed Internet. For stub operation,
routing interoperability in the near term may be achieved using some
combination of mechanisms such as MANET-based anycast and mobile IP.
Future interoperability may be achieved using mechanisms other than
mobile IP.
Interaction with Standard IP Routing will be greatly facilitated by
usage of a common MANET addressing approach by all MANET routing
protocols. Development of such an approach is underway which permits
routing through a multi-technology fabric, permits multiple hosts per
router and ensures long-term interoperability through adherence to
the IP addressing architecture. Supporting these features appears
only to require identifying host and router interfaces with IP
addresses, identifying a router with a separate Router ID, and
permitting routers to have multiple wired and wireless interfaces.
6. MANET Routing Protocol Performance Issues
To judge the merit of a routing protocol, one needs metrics--both To judge the merit of a routing protocol, one needs metrics--both
qualitative and quantitative--with which to measure its suitability qualitative and quantitative--with which to measure its suitability
and performance. These metrics should be *independent* of any given and performance. These metrics should be *independent* of any given
routing protocol. routing protocol.
The following is a list of desirable qualitative properties of manet The following is a list of desirable qualitative properties of manet
routing protocols. routing protocols.
1) Distributed operation: This is an essential property, but it 1) Distributed operation: This is an essential property, but it
should be stated nonetheless. should be stated nonetheless.
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data routing performance (e.g., means, variances, distributions) data routing performance (e.g., means, variances, distributions)
are important. These are the measures of a routing policy's are important. These are the measures of a routing policy's
effectiveness--how well it does its job--as measured from the effectiveness--how well it does its job--as measured from the
*external* perspective of other policies that make use of routing. *external* perspective of other policies that make use of routing.
2) Route Acquisition Time: A particular form of *external* end- 2) Route Acquisition Time: A particular form of *external* end-
to-end delay measurement--of particular concern with "on demand" to-end delay measurement--of particular concern with "on demand"
routing algorithms--is the time required to establish route(s) routing algorithms--is the time required to establish route(s)
when requested. when requested.
3) Efficiency: If data routing effectiveness is the external 3) Percentage Out-of-Order Delivery: An external measure of
connectionless routing performance of particular interest to
transport layer protocols such as TCP which prefer in-order
delivery.
4) Efficiency: If data routing effectiveness is the external
measure of a policy's performance, efficiency is the *internal* measure of a policy's performance, efficiency is the *internal*
measure of its effectiveness. To achieve a given level of data measure of its effectiveness. To achieve a given level of data
routing performance, two different policies can expend differing routing performance, two different policies can expend differing
amounts of overhead, depending on their internal efficiency. amounts of overhead, depending on their internal efficiency.
Protocol efficiency may or may not directly affect data routing Protocol efficiency may or may not directly affect data routing
performance. If control and data traffic must share the same performance. If control and data traffic must share the same
channel, and the channel's capacity is limited, then excessive channel, and the channel's capacity is limited, then excessive
control traffic often impacts data routing performance. control traffic often impacts data routing performance.
It is useful to track two ratios that illuminate the *internal* It is useful to track two ratios that illuminate the *internal*
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These attributes of a protocol can typically be expressed These attributes of a protocol can typically be expressed
*qualitatively*, e.g., whether the protocol can or cannot support *qualitatively*, e.g., whether the protocol can or cannot support
shortest-path routing. Qualitative descriptions of this nature shortest-path routing. Qualitative descriptions of this nature
permit broad classification of protocols, and form a basis for more permit broad classification of protocols, and form a basis for more
detailed *quantitative* assessments of protocol performance. In detailed *quantitative* assessments of protocol performance. In
future documents, the group may put forth candidate recommendations future documents, the group may put forth candidate recommendations
regarding protocol design for MANETs. The metrics and the philosophy regarding protocol design for MANETs. The metrics and the philosophy
presented within this document are expected to continue to evolve as presented within this document are expected to continue to evolve as
MANET technology and related efforts mature. MANET technology and related efforts mature.
6. References 7. Security Considerations
Mobile wireless networks are generally more prone to physical
security threats than are fixed, hardwired networks. Existing link-
level security techniques (e.g. encryption) are often applied within
wireless networks to reduce these threats. Absent link-level
encryption, at the network layer, the most pressing issue is one of
inter-router authentication prior to the exchange of network control
information. Several levels of authentication ranging from no
security (always an option) and simple shared-key approaches, to full
public key infrastructure-based authentication mechanisms will be
explored by the group. As an adjunct to the working groups efforts,
several optional authentication modes may be standardized for use in
MANETs.
8. References
[1] B. Adamson, "Tactical Radio Frequency Communication Requirements for [1] B. Adamson, "Tactical Radio Frequency Communication Requirements for
IPng," RFC 1677, Aug. 1994. IPng," RFC 1677, Aug. 1994.
Authors' Addresses Authors' Addresses
M. Scott Corson M. Scott Corson
Institute for Systems Research Institute for Systems Research
University of Maryland University of Maryland
College Park, MD 20742 College Park, MD 20742
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