One document matched: draft-ali-arp-over-gmpls-controlled-ethernet-psc-i-04.txt
Differences from draft-ali-arp-over-gmpls-controlled-ethernet-psc-i-03.txt
CCAMP Working Group Zafar Ali
Hassan Sheikh
Internet Draft Cisco Systems, Inc.
Tomohiro Otani
KDDI R&D Laboratories, Inc.
Intended status: BCP July 9,
2007
Expires: January 2008
Address Resolution for GMPLS controlled PSC Ethernet Interfaces
draft-ali-arp-over-gmpls-controlled-ethernet-psc-i-04.txt
Status of this Memo
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Copyright Notice
Copyright (C) The IETF Trust (2007).
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Abstract
This document outlines some interoperability issues observed with
the use of ARP over GMPLS controlled Ethernet router-to-router
(PSC) interfaces transiting from a non-Ethernet core, e.g., FSC
or LSC GMPLS core. The document also recommends some procedures
to address these issues. The aim of this document is to
facilitate and ensure better interworking of GMPLS-capable Label
Switching Routers (LSRs), based on experience gained in
interoperability testing.
Conventions used in this document
In examples, "C:" and "S:" indicate lines sent by the client and
server respectively.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
RFC-2119.
Table of Contents
1. Introduction...............................................2
2. Address to use for ARP Resolution..........................5
3. Security Considerations....................................5
4. IANA Considerations........................................5
5. References.................................................5
5.1. Normative References..................................5
5.2. Informative References................................5
Author's Addresses............................................6
Intellectual Property Statement...............................6
Disclaimer of Validity........................................7
1. Introduction
This draft addresses the scenario where edge routers are
connected via a non-Ethernet switch capable GMPLS core, e.g., FSC
or LSC core [RFC3471], [RFC3473]. Furthermore, the interfaces
between the router and the optical device (OXC) are Ethernet, and
considered as point-to-point. Unlike POS links where a L2
adjacency resolution is not required, the Ethernet links require
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that the ARP be resolved (also known as Layer 2 MAC address)
before any forwarding works on this link.
This draft addresses the following scenario,
<---------------------- GMPLS Tunnel ----------------------->
RTR1 <---- GE TE link ----> OXC <---- GE TE link ----> RTR2
segment # 1 segment # 2
Figure 1: Reference Diagram.
Here TE links can be numbered or unnumbered. Similarly, tunnel
interface can be numbered or unnumbered. Furthermore, segment # 1
and segment #2 may or may not be in the same subnets.
When an LSP Path is established between the Ingress Router (RTR1)
to Egress Router (RTR2), Ethernet interface at the two routers
comes up. However, before this LSP (or interface) can forward any
IP traffic, MAC address of the remote router needs to be
resolved. The remote MAC address learning is the same procedure
used in ARP resolution to be able to map and ip address to a MAC
address on an Ethernet segment.
End-point MAC address needs to be re-learned once the ARP cache
entries time-out, or every time the path taken by the GMPLS LSP
changes (e.g., due to re-routing or re-optimization). This
introduces latency that is at least equal to the round trip
delay. Such latency adds to the traffic switchover delay and
consequently traffic loss for 1:1 protected LSP without extra
traffic, or when LSP route changes due to re-routing
(restoration) or re-optimization, etc.
Interoperability issues in learning end-point MAC address using
ARP are also found among vendors at various Interoperability
events/ testing efforts. This is because different vendors use
different IP address for ARP resolution. Some LSR vendor uses the
address of the TE link at the end-point, while others adapt to
use tunnel interface address for ARP resolution. When both end-
point TE link address and tunnel interface addresses are
unnumbered, the ARP needs to be performed using loopback
addresses or unique node-ids. Some LSRs do not reply to ARP
request sent to a loopback address unless proxy Arp is used or
unless there is no issues with the L3 reachability of such
loopback address. When tunnel interface is protected, i.e., it
has working and protecting LSP-es, the ARP requested for a given
tunnel IF address should resolve ARP for the physical interfaces
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along the path of working and protecting LSP. Issue associated
with ARP latency and traffic loss for 1:1 protected LSP without
extra traffic, or when LSP route changes due to due to re-routing
(restoration) or re-optimization, etc. could not be addressed.
Furthermore tunnel IF address can also be unnumbered.
This document provides some recommendations for the use of the
MAC addresses resolution (ARP resolution) for a GMPLS LSP. In the
following, we provide reason behind recommendations provided in
this document.
Consider following scenarios. Please refer to Figure 1.
1. When numbered TE links are used but segment # 1 and segment #
2 are in different subnets: In this case disjoint subnets are
used with numbered TE links between the Ingress LSR and the
Optical node, and the Egress LSR and the optical node. In this
situation we really have no way of resolving ARP using the
addresses of the underlying TE link Ethernet links without
using static ARP entries. The issue is that the subnets are
different so the ARP request received by RTR2 from RTR1 will
be rejected as it is not known to RTR2, and vice versa.
Instead, if the ARP request if for the GMPLS tunnel instead
then there should be no problem as the GMPLS tunnel is point-
to-point virtual link with IPV4 addresses in the same subnet.
2. When the GMPLS tunnel is numbered but the TE links are
Unnumbered and RTR1 does not have loopback address used by RTR2
in its forwarding database, and vice versa. An example of such
scenario is the case when optical and packet TE links are
flooded with different IGP instances. In this case, we are
again faced with the same issue of L2 ARP adjacency resolution
between RTR1 and RTR2. RTR2 will reject the ARP request for
RTR1 as it will not find the unnumbered address (used by RTR1)
in its forwarding database. This issue would not be
encountered if we were resolving the ARP on GMPLS tunnel
address.
3. If the GMPLS tunnel is unnumbered then the ARP resolution
needs to be done using Loopback addresses associated with the
GMPLS tunnel.
4. GMPLS Protection Case: The use of the GMPLS tunnel IP address
for ARP resolution can also be extended to the case where the
GMPLS tunnel is providing 1:1 protection i.e. a working LSP
and a protected LSP exists for the GMPLS tunnel. The protected
and the working LSP of the GMPLS tunnel are typically using
different physical interfaces with different MAC address and
TE link addresses. In this case, using the same GMPLS tunnel
IP addresses for resolving ARP for both working and the
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protecting links would require the router to associate two
physical interfaces with different MAC addresses with the same
GMPLS tunnel IP address. The use of this implementation along
with the creation of such mapping would also eliminate the
problem of ARP cache timeout on the protecting link; and hence
can address the above-mentioned ARP latency issue related to
protection/ restoration or reoptimization case.
2. Address to use for ARP Resolution
An LSR SHOULD use tunnel interface address for ARP request. An
LSR, based on a local decision, can determine if the Interface is
point-to-point and SHOULD resolve APR using loopback addresses.
Similarly, for point-to-point interfaces, an LSR SHOULD resolve
APR for two or more physical interfaces using the same IP address
(this is to address ARP Latency issue mentioned-above).
In the case of protected tunnels, the ARP cache SHOULD NOT
timeout the ARP entry on both the working and the protecting
LSPs. To meet this requirement, an LSR MAY resolve the ARP at the
GMPLS tunnel setup time and MAY use an infinite ARP timeout (this
is to make sure that ARP entire will not timeout as long as the
GMPLS tunnel is UP). Alternatively, an LSR MAY implement a
periodic ARP refresh scheme for the GMPLS tunnel to keep the ARP
cache refreshed for both the working and the protected LSP.
3. Security Considerations
This document does not introduce new security issues.
4. IANA Considerations
This document does not require any IANA consideration.
5. References
5.1. Normative References
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5.2. Informative References
[RFC3471] Generalized Multi-Protocol Label Switching (GMPLS)
Signaling Functional Description, RFC 3471, L. Berger, et al,
January 2003.
[RFC3473] "Generalized Multi-Protocol Label Switching (GMPLS)
Signaling Resource ReserVation Protocol-Traffic Engineering
(RSVP-TE) Extensions", RFC 3473, L. Berger, et al, January
2003.
Author's Addresses
Zafar Ali
Cisco Systems Inc.
2000 Innovation Dr.,
Kanata, Ontario, K2K 3E8
Canada.
Phone: (613) 889-6158
Email: zali@cisco.com
Hassan Sheikh
Cisco Systems Inc.
2000 Innovation Dr.,
Kanata, Ontario, K2K 3E8
Canada.
Phone: (613) 254-3356
Email: hassans@cisco.com
Tomohiro Otani
KDDI R&D Laboratories, Inc.
2-1-15 Ohara Fujimino-shi
Saitama, 356-8502. Japan
Phone: +81-49-278-7357
Email: otani@kddilabs.jp
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