Network Working Group Yiqun Cai
Internet-Draft Microsoft
Intended status: Standards Track Sri Vallepalli
Expires: August 19, 2014 Heidi Ou
Cisco Systems, Inc.
Andy Green
British Telecom
February 15, 2014
PIM Designated Router Load Balancing
draft-ietf-pim-drlb-03.txt
Abstract
On a multi-access network, one of the PIM routers is elected as a
Designated Router (DR). On the last hop network, the PIM DR is
responsible for tracking local multicast listeners and forwarding
traffic to these listeners if the group is operated in PIM SM. In
this document, we propose a modification to the PIM SM protocol that
allows more than one of these last hop routers to be selected so that
the forwarding load can be distributed to and handled among these
routers.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
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."
This Internet-Draft will expire on August 19, 2014.
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
Yiqun Cai, et al. Expires August 19, 2014 [Page 1]
Internet-Draft PIMv2 DR Load Balancing February 2014
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Functional Overview . . . . . . . . . . . . . . . . . . . . . 6
4.1. GDR Candidates . . . . . . . . . . . . . . . . . . . . . . 7
4.2. Hash Mask . . . . . . . . . . . . . . . . . . . . . . . . 7
4.3. PIM Hello Options . . . . . . . . . . . . . . . . . . . . 8
5. Hello Option Formats . . . . . . . . . . . . . . . . . . . . . 9
5.1. PIM DR Load Balancing Capability (DRLBC) Hello Option . . 9
5.2. PIM DR Load Balancing GDR (DRLBGDR) Hello Option . . . . . 10
6. Protocol Specification . . . . . . . . . . . . . . . . . . . . 11
6.1. PIM DR Operation . . . . . . . . . . . . . . . . . . . . . 11
6.2. PIM GDR Candidate Operation . . . . . . . . . . . . . . . 11
6.3. PIM Assert Modification . . . . . . . . . . . . . . . . . 12
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
8. Security Considerations . . . . . . . . . . . . . . . . . . . 14
9. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 14
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
10.1. Normative Reference . . . . . . . . . . . . . . . . . . . 14
10.2. Informative References . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15
Yiqun Cai, et al. Expires August 19, 2014 [Page 2]
Internet-Draft PIMv2 DR Load Balancing February 2014
1. Terminology
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 [RFC2119].
With respect to PIM, this document follows the terminology that has
been defined in [RFC4601].
This document also introduces the following new acronyms:
o GDR: GDR stands for "Group Designated Router". For each multicast
group, a hash algorithm (described below) is used to select one of
the routers as a GDR. The GDR is responsible for initiating the
forwarding tree building for the corresponding group.
o GDR Candidate: a last hop router that has potential to become a
GDR. A GDR Candidate must have the same DR priority and must run
the same GDR election hash algorithm as the DR router. It must
send and process received new PIM Hello Options as defined in this
document. There might be more than one GDR Candidate on a LAN.
But only one can become GDR for a specific multicast group.
2. Introduction
On a multi-access network such as an Ethernet, one of the PIM routers
is elected as a DR. The PIM DR has two roles in the PIM protocol.
On the first hop network, the PIM DR is responsible for registering
an active source with the Rendezvous Point (RP) if the group is
operated in PIM SM. On the last hop network, the PIM DR is
responsible for tracking local multicast listeners and forwarding to
these listeners if the group is operated in PIM SM.
Consider the following last hop network in Figure 1:
Yiqun Cai, et al. Expires August 19, 2014 [Page 3]
Internet-Draft PIMv2 DR Load Balancing February 2014
( core networks )
| | |
| | |
R1 R2 R3
| | |
--(last hop LAN)--
|
|
(many receivers)
Figure 1: Last Hop Network
Assume R1 is elected as the Designated Router. According to
[RFC4601], R1 will be responsible for forwarding to the last hop LAN.
In addition to keeping track of IGMP and MLD membership reports, R1
is also responsible for initiating the creation of source and/or
shared trees towards the senders or the RPs.
Forcing sole data plane forwarding responsibility on the PIM DR
proves a limitation in the protocol. In comparison, even though an
OSPF DR, or an IS-IS DIS, handles additional duties while running the
OSPF or IS-IS protocols, they are not required to be solely
responsible for forwarding packets for the network. On the other
hand, on a last hop LAN, only the PIM DR is asked to forward packets
while the other routers handle only control traffic (and perhaps drop
packets due to RPF failures). The forwarding load of a last hop LAN
is concentrated on a single router.
This leads to several issues. One of the issues is that the
aggregated bandwidth will be limited to what R1 can handle towards
this particular interface. These days, it is very common that the
last hop LAN usually consists of switches that run IGMP/MLD or PIM
snooping. This allows the forwarding of multicast packets to be
restricted only to segments leading to receivers who have indicated
their interest in multicast groups using either IGMP or MLD. The
emergence of the switched Ethernet allows the aggregated bandwidth to
exceed, some times by a large number, that of a single link. For
example, let us modify Figure 1 and introduce an Ethernet switch in
Figure 2.
Yiqun Cai, et al. Expires August 19, 2014 [Page 4]
Internet-Draft PIMv2 DR Load Balancing February 2014
( core networks )
| | |
| | |
R1 R2 R3
| | |
+=gi0===gi1===gi2=+
+ +
+ switch +
+ +
+=gi4===gi5===gi6=+
| | |
H1 H2 H3
Figure 2: Last Hop Network with Ethernet Switch
Let us assume that each individual link is a Gigabit Ethernet. Each
router, R1, R2 and R3, and the switch have enough forwarding capacity
to handle hundreds of Gigabits of data.
Let us further assume that each of the hosts requests 500 mbps of
data and different traffic is requested by each host. This
represents a total 1.5 gbps of data, which is under what each switch
or the combined uplink bandwidth across the routers can handle, even
under failure of a single router.
On the other hand, the link between R1 and switch, via port gi0, can
only handle a throughput of 1gbps. And if R1 is the only router, the
PIM DR elected using the procedure defined by RFC 4601, at least 500
mbps worth of data will be lost because the only link that can be
used to draw the traffic from the routers to the switch is via gi0.
In other words, the entire network's throughput is limited by the
single connection between the PIM DR and the switch (or the last hop
LAN as in Figure 1).
The problem may also manifest itself in a different way. For
example, R1 happens to forward 500 mbps worth of unicast data to H1,
and at the same time, H2 and H3 each requests 300 mbps of different
multicast data. Once again packet drop happens on R1 while in the
mean time, there is sufficient forwarding capacity left on R2 and R3
and link capacity between the switch and R2/R3.
Another important issue is related to failover. If R1 is the only
forwarder on the last hop network, in the event of a failure when R1
goes out of service, multicast forwarding for the entire network has
to be rebuilt by the newly elected PIM DR. However, if there was a
way that allowed multiple routers to forward to the network for
different groups, failure of one of the routers would only lead to
Yiqun Cai, et al. Expires August 19, 2014 [Page 5]
Internet-Draft PIMv2 DR Load Balancing February 2014
disruption to a subset of the flows, therefore improving the overall
resilience of the network.
In this document, we propose a modification to the PIM protocol that
allows more than one of these routers, called Group Designated Router
(GDR) to be selected so that the forwarding load can be distributed
to and handled by a number of routers.
3. Applicability
The proposed change described in this specification applies to PIM SM
last hop routers only.
It does not alter the behavior of a PIM DR on the first hop network
This is because the source tree is built using the IP address of the
sender, not the IP address of the PIM DR that sends the registers
towards the RP. The load balancing between first hop routers can be
achieved naturally if an IGP provides equal cost multiple paths
(which it usually does in practice). And distributing the load to do
registering does not justify the additional complexity required to
support it.
4. Functional Overview
In the existing PIM DR election, when multiple last hop routers are
connected to a multi-access network (for example, an Ethernet), one
of them is selected to act as PIM DR. The PIM DR is responsible for
sending Join/Prune messages towards the RP or source. To elect the
PIM DR, each PIM router on the network examines the received PIM
Hello messages and compares its DR priority and IP address with those
of its neighbors. The router with the highest DR priority is the PIM
DR. If there are multiple such routers, their IP addresses are used
as the tie-breaker, as described in [RFC4601].
In order to share forwarding load among last hop routers, besides the
normal PIM DR election, the GDR is also elected on the last hop
multi-access network. There is only one PIM DR on the multi-access
network, but there might be multiple GDR Candidates.
For each multicast group, a hash algorithm is used to select one of
the routers to be the GDR. Hash Masks are defined for Source, Group
and RP separately, in order to handle PIM ASM/SSM. The masks are
announced in PIM Hello by DR as a DR Load Balancing GDR (DRLBGDR)
Hello Option. Besides that, a DR Load Balancing Capability (DRLBC)
Hello Option, which contains hash algorithm type, is also announced
by router interfaces which have this specification supported. Last
Yiqun Cai, et al. Expires August 19, 2014 [Page 6]
Internet-Draft PIMv2 DR Load Balancing February 2014
hop routers who are with the new DRLBC Option, and with the same GDR
election hash algorithm and the same DR priority as the PIM DR are
GDR Candidates.
A hash algorithm based on the announced Source, Group or RP masks
allows one GDR to be assigned to a corresponding multicast group, and
that GDR is responsible for initiating the creation of the multicast
forwarding tree for the group.
4.1. GDR Candidates
GDR is the new concept introduced by this specification. GDR
Candidates are routers eligible for GDR election on the LAN. To
become a GDR Candidate, a router MUST support this specification,
have the same DR priority and run the same GDR election hash
algorithm as the DR on the LAN.
For example, assume there are 4 routers on the LAN: R1, R2, R3 and
R4, which all support this specification on the LAN. R1, R2 and R3
have the same DR priority while R4's DR priority is less preferred.
In this example, R4 will not be eligible for GDR election, because R4
will not become a PIM DR unless all of R1, R2 and R3 go out of
service.
Further assume router R1 wins the PIM DR election, and R1, R2 run the
same hash algorithm for GDR election, while R3 runs a different one.
Then only R1 and R2 will be eligible for GDR election, R3 will not.
As a DR, R1 will include its own Load Balancing Hash Masks, and also
the identity of R1 and R2 (the GDR Candidates) in its DRLBGDR Hello
Option.
4.2. Hash Mask
A Hash Mask is used to extract a number of bits from the
corresponding IP address field (32 for v4, 128 for v6), and calculate
a hash value. A hash value is used to select a GDR from GDR
Candidates advertised by PIM DR. For example, 0.255.0.0 defines a
Hash Mask for an IPv4 address that masks the first, the third and the
fourth octets.
There are three Hash Masks defined,
o RP Hash Mask
o Source Hash Mask
o Group Hash Mask
The Hash Masks MUST be configured on the PIM routers that can
Yiqun Cai, et al. Expires August 19, 2014 [Page 7]
Internet-Draft PIMv2 DR Load Balancing February 2014
potentially become a PIM DR.
A simple Modulo hash algorithm will be discussed in this document.
However, to allow other hash algorithm to be used, a 4-bytes "Hash
Algorithm Type" field is included in DRLBC Hello Option to specify
the hash algorithm used by a last hop router.
If different hash algorithm types are advertised among last hop
routers, only last hop routers running the same hash algorithm as the
DR (and having the same DR priority as the DR) are eligible for GDR
election.
For ASM groups, a hash value is calculated using the following Modulo
algorithm:
o hashvalue_RP = (((RP_address & RP_hashmask) >> N) & 0xFFFF) % M
RP_address is the address of the RP defined for the group. N is the
number of zeros, counted from the least significant bit of the
RP_hashmask. For example, for a given IPv4 RP_hashmask 0.255.0.0, N
will be 16. M is the number of GDR Candidates as described above.
If RP_hashmask is 0, a hash value is also calculated using the group
Hash Mask in a similar fashion.
o hashvalue_Group = (((Group_address & Group_hashmask) >> N) &
0xFFFF) % M
For SSM groups, a hash value is calculated using both the source and
group Hash Mask
o hashvalue_SG = ((((Source_address & Source_hashmask) >> N_S) &
0xFFFF) ^ (((Group_address & Group_hashmask) >> N_G) & 0xFFFF)) %
M
4.3. PIM Hello Options
When a last hop PIM router sends a PIM Hello from an interface with
this specificiation support, it includes a new option, called "Load
Balancing Capability (DRLBC)".
Besides this DRLBC Hello Option, the elected PIM DR also includes a
new "DR Load Balancing GDR (DRLBGDR) Hello Option". The DRLBGDR
Hello Option consists of three Hash Masks as defined above and also
the sorted addresses of all GDR Candidates on the last hop network.
The elected PIM DR uses DRLBC Hello Option advertised by all routers
on the last hop network to compose its DRLBGDR . The GDR Candidates
Yiqun Cai, et al. Expires August 19, 2014 [Page 8]
Internet-Draft PIMv2 DR Load Balancing February 2014
use DRLBGDR Hello Option advertised by PIM DR to calculate hash
value.
5. Hello Option Formats
5.1. PIM DR Load Balancing Capability (DRLBC) Hello Option
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = TBD | Length = 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Hash Algorithm Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Capability Hello Option
Type: TBD.
Length: 4 octets
Hash Algorithm Type: 0 for Modulo hash algorithm
This DRLBC Hello Option SHOULD be advertised by last hop routers from
interfaces which support this specification.
Yiqun Cai, et al. Expires August 19, 2014 [Page 9]
Internet-Draft PIMv2 DR Load Balancing February 2014
5.2. PIM DR Load Balancing GDR (DRLBGDR) Hello Option
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = TBD | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Group Mask |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Mask |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RP Mask |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GDR Candidate Address(es) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: GDR Hello Option
Type: TBD
Length:
Group Mask (32/128 bits): Mask
Source Mask (32/128 bits): Mask
RP Mask (32/128 bits): Mask
All masks MUST be in the same address family, with the same
length.
GDR Address (32/128 bits): Address(es) of GDR Candidate(s)
All addresses must be in the same address family. The addresses
are sorted from high to low. The order is converted to the
ordinal number associated with each GDR candidate in hash value
calculation. For example, addresses advertised are R3, R2, R1,
the ordinal number assigned to R3 is 0, to R2 is 1 and to R1 is 2.
If "Interface ID" option (type 31) presents in a GDR Candicate's
PIM Hello message, and the "Router ID" portion is non-zero,
* For IPv4, the "GDR Candidate Address" will be set directly to
"Router ID".
* For IPv6, the "GDR Candidate Address" will be set to the IPv4-
IPv6 translated address of "Router ID", as described in
[RFC4291], that is the "Router-ID" is appended to the prefix of
96-bits zeros.
Yiqun Cai, et al. Expires August 19, 2014 [Page 10]
Internet-Draft PIMv2 DR Load Balancing February 2014
If the "Interface ID" option is not present in a GDR Candidate's
PIM Hello message, or if the "Interface ID" option is present,
but"Router ID" field is zero, the "GDR Candidate Address" will be
the IPv4 or IPv6 source address from PIM Hello message.
This DRLBGDR Hello Option SHOULD only be advertised by the elected
PIM DR.
6. Protocol Specification
6.1. PIM DR Operation
The DR election process is still the same as defined in [RFC4601]. A
DR that has this specification enabled on the interface, advertises
the new LBGRD Hello Option, which contains value of masks from user
configuration, followed by a sorted list of addresses of all GDR
Candidates. Moreover, same as non-DR routers, DR also advertises
DRLBC Hello Option to indicate its capability of supporting this
specification and the type of its GDR election hash algorithm.
If a PIM DR receives a neighbor Hello with DRLBGRD Option, the PIM DR
SHOULD ignore the TLV.
If a PIM DR receives a neighbor DRLBC Hello Option, which contains
the same hash algorithm type as the DR, and the neighbor has the same
DR priority as the DR, PIM DR SHOULD consider the neighbor as a GDR
Candidate and insert the neighbor's address into the sorted list of
DRLBGRD Option.
6.2. PIM GDR Candidate Operation
When an IGMP join is received, without this proposal, router R1 (the
PIM DR) will handle the join and potentially run into the issues
described earlier. Using this proposal, a hash algorithm is used to
determine which router is going to be responsible for building
forwarding trees on behalf of the host.
The algorithm works as follows, assuming the router in question is X,
which is a GDR Candidate, and its ordinal number assigned implicitly
by PIM DR in DRLBGDR Hello Option is Ox:
o If the group is ASM, and the RP Hash Mask announced by the PIM DR
is not zero, calculate the value of hashvalue_RP. If hashvalue_RP
is equal to Ox, X becomes the GDR.
For example, X with IPv4 address 10.1.1.3, receives a DRLBGDR Hello
Option from the DR, which announces RP Hash Mask 0.255.0.0, and a
Yiqun Cai, et al. Expires August 19, 2014 [Page 11]
Internet-Draft PIMv2 DR Load Balancing February 2014
list of GDR Candidates, sorted by IP addresses from high to low,
10.1.1.3, 10.1.1.2 and 10.1.1.1. The ordinal number assigned to
those addresses would be 0 for 10.1.1.3 (X), 1 for 10.1.1.2, and 2
for 10.1.1.1. Assume there are 2 RPs: RP1 172.3.10.10 for Group1 and
RP2 172.2.10.10 for Group2. Following the modulo hash algorithm
hashvalue_RP = (((RP_address & RP_hashmask) >> N) & 0xFFFF) % M
Here N is 16 for 0.255.0.0, and M is 3 for the total number of GDR
Candidates. The hasvalue_RP for RP1 172.3.10.10 is 0, matches the
ordinal number assigned to X. X will be the GDR for Group1, which
uses 172.3.10.10 as the RP. The hashvalue_RP for RP2 172.2.10.10 is
2, which is different from X's ordinal number, hence, X will not be
GDR for Group2.
o If the group is ASM, and the RP Hash Mask announced by the PIM DR
is zero, obtain the value of hashvalue_Group. Compare
hashvalue_Group with Ox, to decide if X is the GDR.
o If the group is SSM, then use hashvalue_SG to determine if X is
the GDR.
If X is the GDR for the group, X will be responsible for building the
forwarding tree.
A router interface where this protocol is enabled advertises DRLBC
Hello Option in its PIM Hello, even if the router may not be a GDR
Candidate.
A GDR Candidate may receive a DRLBGDR Hello Option from PIM DR, with
different Hash Masks from those configured on it, The GDR Candidate
must use the Hash Masks advertised by the PIM DR to calculate the
hash value.
A GDR Candidate may receive a DRLBGDR Hello Option from a non-DR PIM
router. The GDR Candidate must ignore such DRLBGDR Hello Option.
A GDR Candidate may receive a Hello from the elected PIM DR, and the
PIM DR does not support this specification. The GDR election
described by this specification will not take place, that is only the
PIM DR joins the multicast tree.
6.3. PIM Assert Modification
It is possible that the identity of the GDR might change in the
middle of an active flow. Examples this could happen include:
1. When a new PIM router comes up
Yiqun Cai, et al. Expires August 19, 2014 [Page 12]
Internet-Draft PIMv2 DR Load Balancing February 2014
2. When a GDR restarts
When the GDR changes, existing traffic might be disrupted.
Duplicates or packet loss might be observed. To illustrate the case,
consider the following scenario: there are two streams G1 and G2. R1
is the GDR for G1, and R2 is the GDR for G2. When R3 comes up
online, it is possible that R3 becomes GDR for both G1 and G2, hence
R2 starts to build the forwarding tree for G1 and G2. If R1 and R2
stop forwarding before R3 completes the process, packet loss might
occur. On the other hand, if R1 and R2 continue forwarding while R3
is building the forwarding trees, duplicates might occur.
This is not a typical deployment scenario but it still might happen.
Here we describe a mechanism to minimize the impact. The motivation
is that we want to minimize packet loss. And therefore, we would
allow a small amount of duplicates and depend on PIM Assert to
minimize the duplication.
When the role of GDR changes as above, instead of immediately
stopping forwarding, R1 and R2 continue forwarding to G1 and G2
respectively, while at the same time, R3 build forwarding trees for
G1 and G2. This will lead to PIM Asserts.
Due to the introduction of GDR, this document suggests the following
modification to the Assert packet: if a router enables this
specification on its downstream interface, but it is not a GDR, it
would adjust its Assert metric to (PIM_ASSERT_INFINITY - 1).
Using the above example, assume R1 and R3 agree on the new GDR, which
is R3. R1 will set its Assert metric as (PIM_ASSERT_INFINITY - 1).
That will make R3, which has normal metric in its Assert as the
Assert winner.
For G2, assume it takes a little bit longer time for R2 to find out
that R3 is the new GDR and still thinks itself being the GDR while R3
already has assumed the role of GDR. Since both R2 and R3 think they
are GDRs, they further compare the metric and IP address. If R3 has
the better routing metric, or same metric but better tie-breaker, the
result will be consistent with GDR selection. If unfortunately, R2
has the better metric or same metric but better tie-breaker R2 will
become the Assert winner and continues to forward traffic. This will
continue until:
1. The next PIM Hello option from DR is seen that selects R3 as the
GDR.
2. R3 will build the forwarding tree and send an Assert.
The process continues until R2 agrees to the selection of R3 as being
the GDR, and set its own Assert metric to (PIM_ASSERT_INFINITY - 1),
which will make R3 the Assert winner. During the process, we will
see intermittent duplication of traffic but packet loss will be
Yiqun Cai, et al. Expires August 19, 2014 [Page 13]
Internet-Draft PIMv2 DR Load Balancing February 2014
minimized. In the unlikely case that R2 never relinquishes its role
as GDR (while every other router thinks otherwise), the proposed
mechanism also helps to keep the duplication to a minimum until
manual intervention takes place to remedy the situation.
7. IANA Considerations
Two new PIM Hello Option Types are required to be assigned to the DR
Load Balancing messages. [HELLO-OPT], this document recommends
34(0x22) as the new "PIM DR Load Balancing Capability Hello Option",
and 35(0x23) as the new "PIM DR Load Balancing GDR Hello Option".
8. Security Considerations
Security of the PIM DR Load Balancing Hello message is only
guaranteed by the security of PIM Hello message, so the security
considerations for PIM Hello messages as described in PIM-SM
[RFC4601] apply here.
9. Acknowledgement
The authors would like to thank Steve Simlo, Taki Millonis for
helping with the original idea, Bill Atwood for review comments, Stig
Venaas, Toerless Eckert and Rishabh Parekh for helpful conversation
on the document.
10. References
10.1. Normative Reference
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas,
"Protocol Independent Multicast - Sparse Mode (PIM-SM):
Protocol Specification (Revised)", RFC 4601, August 2006.
10.2. Informative References
[RFC3973] Adams, A., Nicholas, J., and W. Siadak, "Protocol
Independent Multicast - Dense Mode (PIM-DM): Protocol
Specification (Revised)", RFC 3973, January 2005.
[RFC5015] Handley, M., Kouvelas, I., Speakman, T., and L. Vicisano,
Yiqun Cai, et al. Expires August 19, 2014 [Page 14]
Internet-Draft PIMv2 DR Load Balancing February 2014
"Bidirectional Protocol Independent Multicast (BIDIR-
PIM)", RFC 5015, October 2007.
[RFC6395] Gulrajani, S. and S. Venaas, "An Interface Identifier (ID)
Hello Option for PIM", RFC 6395, October 2011.
[RFC4291] Hinden, R. and L. S., "IP Version 6 Addressing
Architecture", RFC 6890, February 2006.
[HELLO-OPT]
IANA, "PIM Hello Options", PIM-HELLO-OPTIONS per
RFC4601 http://www.iana.org/assignments/pim-hello-options,
March 2007.
Authors' Addresses
Yiqun Cai
Microsoft
La Avenida
Mountain View, CA 94043
USA
Email: yiqunc@microsoft.com
Sri Vallepalli
Cisco Systems, Inc.
Tasman Drive
San Jose, CA 95134
USA
Email: svallepa@cisco.com
Heidi Ou
Cisco Systems, Inc.
Tasman Drive
San Jose, CA 95134
USA
Email: hou@cisco.com
Yiqun Cai, et al. Expires August 19, 2014 [Page 15]
Internet-Draft PIMv2 DR Load Balancing February 2014
Andy Green
British Telecom
Adastral Park
Ipswich IP5 2RE
United Kingdom
Email: andy.da.green@bt.com
Yiqun Cai, et al. Expires August 19, 2014 [Page 16]
