Software-based Wireless Router System
This project explores new designs
for access routers that provide IP connectivity to mobile clients
that use wireless links to connect to the network infrastructure.
Several access points are usually connected to a single access
router using wired links, and each access point provides wireless
connection to every mobile client inside its cell.
The motivation for a new router
design comes from the fact that the implementation and deployment
of mobility-aware and channel-adaptive protocols and services
on edge routers pose new requirements from the router system:
they require link-layer support from the system, and in particular
link-layer information about the clients. For example, mobility
management protocols require knowledge on when a mobile client
joined/left the network. Additionally, channel-adaptive protocols
for Quality of Service, such as wireless schedulers, require
periodic measurements on the quality of the channel each host
perceives. Moreover, the enforcement of network-level policies
often requires mechanisms that are available only at the link-layer.
As an example, to deny a mobile node access to the network,
some form of "physical" disconnection is needed.
Current routers though do not provide
this link-layer support to services designed and developed for
wireless environments, making difficult, if not impossible,
their implementation and deployment.
DIRAC solves the above problem,
and makes link-layer information and mechanisms available to
wireless services by following a distributed design approach.
It consists of two software modules:
Core (RC), which implements the main
forwarding functionality, along with the (wireless) router services
and protocols, and
Agents (RAs), each one of which runs
on an access point, and is responsible for collecting and reporting
information to the RC, and also enabling link-layer mechanisms
for use by the RC..
Using the DIRAC framework, we implemented
three wireless router services:
- A micro-mobility management protocol that
minimizes transient packet losses during handoffs
- An FEC-based packet forwarding solution
that solves the Head-of-Line (HoL) blocking problem over wireless
- A link-layer assisted policing mechanism
that penalizes overly aggressive, wireless clients.
- "DIRAC: A Software-based Wireless Router System".
Petros Zerfos, Gary Zhong, Jerry Cheng, Haiyun Luo, Songwu Lu,
Jia-Ru Li, In Proc. of ACM MOBICOM 2003 [ps]
- "Architecture Taxonomy for Control and Provisioning of
Wireless Access Points (CAPWAP)",
Lily Yang, Petros Zerfos, Emek Sadot,
IETF Internet Draft (work in progress) [txt]
- "DIRAC: A Software-based Wireless Router System",
presented at ACM MOBICOM, Sep. 2003 and also Nokia Research Center,
Mountain View, CA, Jun. 2003 [pdf]