Ethernet

BROADBAND INTERNET ACCESS USING GIGABIT ETHERNET OVER WAVELENGTH-DIVISION MULTIPLEXING WDM NETWORKS
Tel: +49 89 289-2-3511 Fax: +49 89 289-6-3511 Institute of Communication Networks Munich University of Technology 80290 Munich - Germany
SDH SONET, Frame Relay, Gigabit Ethernet and some proprietary solutions. This paper focuses on the transmission of IP over Gigabit Ethernet over WDM, withGigabit Ethernet providing a cost-e ective alternative for IP over WDM. The paper is organized as follows. In section 2 relevant aspects concerning Gigabit Ethernet are given and section 3 describes generic network architectures.
Schupke@ei.tum.de

D.A. Schupke

Abstract

This paper deals with the architectural issues and bene ts of operating Gigabit Ethernet over wavelength-divisionmultiplexing WDM networks to provide broadband access to Internet networks.

Internet Access, Gigabit Ethernet, Wavelength-Division Multiplex, IP over WDM
Keywords:

1 Introduction
The popularity of the Internet leads to an increasing number of emerging applications operating with the corresponding Internet protocol IP. High bandwidth transmission over Internet links is one building block toprovide audio & video applications apart from common data transport over the Internet protocol, thus enabling applications like computer-supported cooperative work CSCW. While these applications may mainly be found in business and university area, new initiatives like the Canadian initiative Gigabit Internet to every Canadian Home by 2005" 1 may encompass to an ever increasing demand even for homeaccess. By extrapolating the demand for the future the need for multiples of nowaday's network capacities is expected. One method for providing high bandwidth on the physical layer is using optical networks and among these in particular those employing wavelengthdivision multiplexing WDM. WDM proves to be economical as existing ber capacity can be extended without requiring the installation ofadditional ber. Moreover WDM equipment like ampli ers operates on aggregated bandwidth i.e. the multiplexed WDM channels simultaneously. There are several layers possible combining IP and WDM for high speeds, among these ATM,

2 Gigabit Ethernet
The Gigabit Ethernet standard 802.3z was dened by the Institute of Electrical and Electronics Engineers IEEE in 1998 2 and is an enhancement of theEthernet types operating with 10 and 100 Mbit s. One strong argument for the choice of Gigabit Ethernet is that Ethernet know-how is usually commonplace with network users and remains widely employable for Gigabit Ethernet. This avoids high personnel training costs. The following describes how Gigabit Ethernet ts into its neighbor upper and lower layers, closing with a short performance analysis.2.1 Interface to the IP Layer

The de nition framework applicable for transmitting IP packets over Gigabit Ethernet is described in the Request for Comments RFC 1042 4 . The encapsulation of IP packets is shown in gure 1. The logical link control LLC subnetwork access protocol SNAP header is needed to be able to distinguish between di erent protocols IP packets have the LLC SNAPheader 0x AA AA 03 00 00 00 08 00. Gigabit Ethernet has a simple interface to the IP layer, since IP packets are mapped directly into

IP Packet

20..1492 Octets Logical Link Control (LLC) 3 Octets Subnetwork Access Protocol (SNAP) 5 Octets IP Packet

Preamble 7 Octets

Start Frame Delimiter (SFD) 1 Octet

Destination Address 6 Octets

Source Address 6 Octets

Length 2 Octets

MACClient Data

Pad 0..18 Octets

Frame Check Sequence (FCS) 4 Octets

Figure 1: Mapping of IP packets into Gigabit Ethernet frames. Gigabit Ethernet frames. By this any Segmentation and Reassembly SAR like in ATM is avoided. Because of the involved hardware complexity of the SAR function currently available ATM router ports feature a maximum capacity of 622 Mbit s 3 , which is lower than the...