draft-ietf-pim-dr-improvement-01.txt   draft-ietf-pim-dr-improvement-02.txt 
PIM WG Zheng. Zhang PIM WG Zheng. Zhang
Internet-Draft Fangwei. Hu Internet-Draft Fangwei. Hu
Intended status: Standards Track BenChong. Xu Intended status: Standards Track BenChong. Xu
Expires: December 8, 2016 ZTE Corporation Expires: June 8, 2017 ZTE Corporation
June 6, 2016 December 5, 2016
PIM DR Improvement PIM DR Improvement
draft-ietf-pim-dr-improvement-01.txt draft-ietf-pim-dr-improvement-02.txt
Abstract Abstract
PIM is worldly deployed multicast protocol. This document will PIM is worldly deployed multicast protocol. This document will
improve the stability of PIM protocol, decrease the lost of multicast improve the stability of PIM protocol, decrease the lost of multicast
packets when the PIM DR (Designed Router) is down. packets when the PIM DR (Designed Router) is down.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
skipping to change at page 1, line 33 skipping to change at page 1, line 33
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
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
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 8, 2016. This Internet-Draft will expire on June 8, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 2, line 17 skipping to change at page 2, line 17
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. PIM hello message format . . . . . . . . . . . . . . . . . . 3 3. PIM hello message format . . . . . . . . . . . . . . . . . . 3
3.1. DR Address Option format . . . . . . . . . . . . . . . . 3 3.1. DR Address Option format . . . . . . . . . . . . . . . . 3
3.2. BDR Address Option format . . . . . . . . . . . . . . . . 4 3.2. BDR Address Option format . . . . . . . . . . . . . . . . 4
4. The Protocol Treatment . . . . . . . . . . . . . . . . . . . 4 4. The Protocol Treatment . . . . . . . . . . . . . . . . . . . 4
4.1. Election Algorithm . . . . . . . . . . . . . . . . . . . 5 4.1. Election Algorithm . . . . . . . . . . . . . . . . . . . 5
4.2. Sending Hello Messages . . . . . . . . . . . . . . . . . 6 4.2. Sending Hello Messages . . . . . . . . . . . . . . . . . 6
4.3. Receiving Hello Messages . . . . . . . . . . . . . . . . 6 4.3. Receiving Hello Messages . . . . . . . . . . . . . . . . 6
4.4. The treatment . . . . . . . . . . . . . . . . . . . . . . 7 4.4. The treatment . . . . . . . . . . . . . . . . . . . . . . 7
5. Deployment suggestion . . . . . . . . . . . . . . . . . . . . 7 5. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 7 6. Deployment suggestion . . . . . . . . . . . . . . . . . . . . 8
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 7. Security Considerations . . . . . . . . . . . . . . . . . . . 8
8. Normative References . . . . . . . . . . . . . . . . . . . . 7 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 9. Normative References . . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction 1. Introduction
Multicast technology is used widely. Many modern technology use PIM Multicast technology is used widely. Many modern technology use PIM
technology, such as IPTV, Net-Meeting, and so on. There are many technology, such as IPTV, Net-Meeting, and so on. There are many
events that will influence the quality of multicast services. The events that will influence the quality of multicast services. The
change of unicast routes will cause the lost of multicast packets. change of unicast routes will cause the lost of multicast packets.
The change of DR cause the lost of multicast packets too. The change of DR cause the lost of multicast packets too.
When a DR on a share-media LAN is down, other routers will elect a When a DR on a share-media LAN is down, other routers will elect a
skipping to change at page 3, line 8 skipping to change at page 3, line 11
------- ------- ------- -------
| | | |
Figure 1: An example of multicast network Figure 1: An example of multicast network
For example, there were two routers on one Ethernet. RouterA was For example, there were two routers on one Ethernet. RouterA was
elected to DR. When RouterA is down, the multicast packets are elected to DR. When RouterA is down, the multicast packets are
discarded until the RouterB is elected to DR and RouterB imports the discarded until the RouterB is elected to DR and RouterB imports the
multicast flows successfully. multicast flows successfully.
We suppose that there is only a RouterA in the Ethernet at first in We suppose that there is only a RouterA in the Ethernet at first in
Figure 1. RouterA is the DR who is responsible for forwarding Figure 1. RouterA is the DR which is responsible for forwarding
multicast flows. When RouterB connects the Ethernet, RouterB will be multicast flows. When RouterB connects the Ethernet, RouterB will be
elected to DR because a higher priority. So RouterA will stop elected to DR because a higher priority. So RouterA will stop
forwarding multicast packets. The multicast flows will not recover forwarding multicast packets. The multicast flows will not recover
until RouterB joins the multicast group after it is elected to DR. until RouterB joins the multicast group after it is elected to DR.
2. Terminology 2. Terminology
Backup Designated Router (BDR): A shared-media LAN like Ethernet may Backup Designated Router (BDR): A shared-media LAN like Ethernet may
have multiple PIM-SM routers connected to it. Except for DR, a have multiple PIM-SM routers connected to it. Except for DR, a
router who will act on behalf of directly connected hosts with router which will act on behalf of directly connected hosts with
respect to the PIM-SM protocol. But BDR will not forward the flows. respect to the PIM-SM protocol. But BDR will not forward the flows.
When DR is down, the BDR will forward multicast flows immediately. A When DR is down, the BDR will forward multicast flows immediately. A
single BDR is elected per interface like the DR. single BDR is elected per interface like the DR.
3. PIM hello message format 3. PIM hello message format
In [RFC4601] and [RFC7761], the PIM hello message format was defined. In [RFC4601] and [RFC7761], the PIM hello message format was defined.
In this document, we define two new option values which are including In this document, we define two new option values which are including
Type, Length, and Value. Type, Length, and Value.
skipping to change at page 4, line 25 skipping to change at page 4, line 25
octets. octets.
o OptionValue: The OptionValue is IP address of BDR. If the network o OptionValue: The OptionValue is IP address of BDR. If the network
is support IPv4, the value is IPv4 address of BDR. If the network is support IPv4, the value is IPv4 address of BDR. If the network
is support IPv6, the value is IPv6 address of BDR. is support IPv6, the value is IPv6 address of BDR.
4. The Protocol Treatment 4. The Protocol Treatment
A new router starts to send hello messages with the values of DR and A new router starts to send hello messages with the values of DR and
BDR are all set to 0 after its interface is enabled in PIM on a BDR are all set to 0 after its interface is enabled in PIM on a
share-media LAN. When the router receive hello messages from other share-media LAN. When the router receives hello messages from other
routers on the same share-media LAN, the router will check if the routers on the same share-media LAN, the router will check if the
value of DR is filled. If the value of DR is filled with IP address value of DR is filled. If the value of DR is filled with IP address
of router who is sending hello messages, the router will store the IP of router which is sending hello messages, the router will store the
address as the DR address of this interface. IP address as the DR address of this interface.
Then the new router compare the priority and IP address itself to the Then the new router compare the priority and IP address itself to the
stored IP address of DR and BDR according to the algorithm of stored IP address of DR and BDR according to the algorithm of
[RFC4601] and [RFC7761]. If the new router notices that it is better [RFC4601] and [RFC7761]. If the new router notices that it is better
to be DR than the existed DR or BDR. The router will make itself the to be DR than the existed DR or BDR. The router will make itself the
BDR, and send new hello messages with its IP address as BDR and BDR, and send new hello messages with its IP address as BDR and
existed DR. If the router notices that the existed DR is most existed DR. If the router notices that the existed DR has the
priority in the share-media LAN, but the existed BDR is set to 0x0 in highest priority in the share-media LAN, but the existed BDR is set
the received hello messages, or the existed BDR is not better than to 0x0 in the received hello messages, or the existed BDR is not
the new router, the router will elect itself to BDR. If the router better than the new router, the new router will elect itself to BDR.
notices that it is not better to be DR than existed DR and BDR, the If the router notices that it is not better to be DR than existed DR
router will respect the PIM protocol. and BDR, the router will respect the existed DR and BDR.
When the new router becomes the new BDR, the router will join the When the new router becomes the new BDR, the router will join the
existed multicast groups, import multicast flows from upstream existed multicast groups, import multicast flows from upstream
routers. But the BDR MUST not forward the multicast flows to avoid routers. But the BDR MUST not forward the multicast flows to avoid
the duplicate multicast packets in the share-media LAN. The new the duplicate multicast packets in the share-media LAN. The new
router will monitor the DR. When the DR becomes unavailable because router will monitor the DR. The method that BDR monitors the DR may
of the down or other reasons, the BDR will forward multicast flows be BFD technology or other ways that can be used to detect link/node
immediately. failure quickly. When the DR becomes unavailable because of the down
or other reasons, the BDR will forward multicast flows immediately.
4.1. Election Algorithm 4.1. Election Algorithm
The DR and BDR election is according the rules defined below, the The DR and BDR election is according the rules defined below, the
algorithm is similar to the DR election definition in [RFC2328]. algorithm is similar to the DR election definition in [RFC2328].
(1) Note the current values for the network's Designated Router and (1) Note the current values for the network's Designated Router and
Backup Designated Router. This is used later for comparison Backup Designated Router. This is used later for comparison
purposes. purposes.
(2) Calculate the new Backup Designated Router for the network as (2) Calculate the new Backup Designated Router for the network as
follows. Those routers that have not declared themselves to be follows. Those routers that have not declared themselves to be
Designated Router are eligible to become Backup Designated Router. Designated Router are eligible to become Backup Designated Router.
The one who have the highest priority will be chosen to be Backup The one which have the highest priority will be chosen to be Backup
Designed Router. In case of a tie, the one having the highest Router Designed Router. In case of a tie, the one having the highest Router
ID is chosen. ID is chosen.
(3) Calculate the new Designated Router for the network as follows. (3) Calculate the new Designated Router for the network as follows.
If one or more of the routers have declared themselves Designated If one or more of the routers have declared themselves Designated
Router (i.e., they are currently listing themselves as Designated Router (i.e., they are currently listing themselves as Designated
Router in their Hello Packets) the one having highest Router Priority Router in their Hello Packets) the one having highest Router Priority
is declared to be Designated Router. In case of a tie, the one is declared to be Designated Router. In case of a tie, the one
having the highest Router ID is chosen. If no routers have declared having the highest Router ID is chosen. If no routers have declared
themselves Designated Router, assign the Designated Router to be the themselves Designated Router, assign the Designated Router to be the
skipping to change at page 5, line 43 skipping to change at page 5, line 43
then proceed to step 5. For example, if Router X is now the then proceed to step 5. For example, if Router X is now the
Designated Router, when step 2 is repeated X will no longer be Designated Router, when step 2 is repeated X will no longer be
eligible for Backup Designated Router election. Among other things, eligible for Backup Designated Router election. Among other things,
this will ensure that no router will declare itself both Backup this will ensure that no router will declare itself both Backup
Designated Router and Designated Router. Designated Router and Designated Router.
(5) As a result of these calculations, the router itself may now be (5) As a result of these calculations, the router itself may now be
Designated Router or Backup Designated Router. Designated Router or Backup Designated Router.
The reason behind the election algorithm's complexity is the desire The reason behind the election algorithm's complexity is the desire
for an orderly transition from Backup Designated Router to Designated for the DR stability.
Router, when the current Designated Router fails. This orderly
transition is ensured through the introduction of hysteresis: no new
Backup Designated Router can be chosen until the old Backup accepts
its new Designated Router responsibilities.
The above procedure may elect the same router to be both Designated The above procedure may elect the same router to be both Designated
Router and Backup Designated Router, although that router will never Router and Backup Designated Router, although that router will never
be the calculating router (Router X) itself. The elected Designated be the calculating router (Router X) itself. The elected Designated
Router may not be the router having the highest Router Priority. If Router may not be the router having the highest Router Priority. If
Router X is not itself eligible to become Designated Router, it is Router X is not itself eligible to become Designated Router, it is
possible that neither a Backup Designated Router nor a Designated possible that neither a Backup Designated Router nor a Designated
Router will be selected in the above procedure. Note also that if Router will be selected in the above procedure. Note also that if
Router X is the only attached router that is eligible to become Router X is the only attached router that is eligible to become
Designated Router, it will select itself as Designated Router and Designated Router, it will select itself as Designated Router and
skipping to change at page 6, line 26 skipping to change at page 6, line 22
interface is in waiting state and start the hold-timer which is like interface is in waiting state and start the hold-timer which is like
the neighbor hold-timer. When the hold-timer is expired, the the neighbor hold-timer. When the hold-timer is expired, the
interface will elect the DR and BDR according to the DR election interface will elect the DR and BDR according to the DR election
rules. rules.
When a new router sets itself BDR after receive hello messages from When a new router sets itself BDR after receive hello messages from
other routers, the router send hello messages with the value of DR is other routers, the router send hello messages with the value of DR is
set to the IP address of existed DR and the value of BDR is set to set to the IP address of existed DR and the value of BDR is set to
the IP address of the router itself. the IP address of the router itself.
When a existed router sets itself non DR and non BDR after receive When a existed BDR sets itself non DR and non BDR after receive hello
hello messages from other routers, the router will send hello messages from other routers, the router will send hello messages with
messages with the value of DR is set to existed DR and the value of the value of DR is set to existed DR and the value of BDR is set to
BDR is set to new BDR. new BDR.
DR newcomer
\ /
----- ----- -----
| A | | B | | C |
----- ----- -----
| | |
| | |
------------------------------------------- LAN
Figure 3
For example, there is a stable LAN that include RouterA and RouterB.
RouterA is the DR which has the best priority. RouterC is a
newcomer. RouterC sends hello packet with the DR and BDR is all set
to zero.
If RouterC cannot send hello packet with the DR/BDR capability,
Router C may send the hello packet according the rule defined
in[RFC4601] and [RFC7761].
4.3. Receiving Hello Messages 4.3. Receiving Hello Messages
When the values of DR and BDR which are carried by hello messages are When the values of DR and BDR which are carried by hello messages are
received is all set to 0x0, the router MUST elect the DR due to the received is all set to 0x0, the router MUST elect the DR due to the
algorithm of [RFC4601] and [RFC7761]. And elect a new BDR which are algorithm of [RFC4601] and [RFC7761] after the hold-timer expires.
the best choice except DR. And elect a new BDR which are the best choice except DR.
When the value of DR which is carried by received hello messages is In case the value of DR which is carried by received hello messages
not 0x0, and the value of BDR is set to 0x0, the router will elect is not 0x0, and the value of BDR is set to 0x0, when the hold-timer
itself to BDR. expires there is no hello packet from other router is received, the
router will elect itself to BDR.
When the values of DR and BDR that carried by received hello messages In case the values of DR and BDR that are carried by received hello
are all larger than 0x0. The router will mark the existed DR, and messages are all larger than 0x0. The router will mark the existed
compare itself and the BDR in message. When the router notice that DR, and compare itself and the BDR in message. When the router
it is better to be DR than existed BDR. The router will elect itself notice that it is better to be DR than existed BDR. The router will
to the BDR. elect itself to the BDR.
When a router receives a new hello message with the values of DR and When a router receives a new hello message with the values of DR and
BDR are set to 0x0. The router will compare the new router with BDR are set to 0x0. The router will compare the new router with
itself. If the router noticed that the new router is better to be DR existed information. If the router noticed that the new router is
than itself, the router will set the BDR to the new router. better to be DR than itself, or the new router is better to be BDR
than the existed BDR, the router will set the BDR to the new router.
As illustrated in Figure 3, after RouterC sends hello packet, RouterC
will not elect the DR until hold-timer expired. During the period,
RouterC should receive the hello packets from RouterA and RouterB.
RouterC accepts the result that RouterA is the DR. In case RouterC
has the lowest priority than RouterA and RouterB, RouterC will also
accept that Router B is the BDR. In case RouterC has the
intermediate priority among the three routers, RouterC will treat
itself as new BDR after the hold-timer expired. In case RouterC has
the highest priority among the three routers, RouterC will treat
RouterA which is the existed DR as DR, and RouterC will treat itself
as new BDR. If the network administrator thinks that RouterC should
be new DR, the DR changing should be triggered manually.
Exception: During the hold-timer period, RouterC receives only the
hello packet from RouterA. When the hold-timer expired, RouterC
treats RouterA as DR. and RouterC treats itself as BDR. In case
RouterC only receives the hello packet from RouterB during the hold-
timer period, RouterC will compare the priority between RouterB and
itself to elect the new DR. In these situations, some interfaces or
links go wrong in the LAN.
4.4. The treatment 4.4. The treatment
When all the routers on a shared-media LAN are start to work on the When all the routers on a shared-media LAN are start to work on the
same time, the election result of DR is same as [RFC4601] and same time, the election result of DR is same as [RFC4601] and
[RFC7761]. And all the routers will elect a BDR which is suboptimum [RFC7761]. And all the routers will elect a BDR which is suboptimum
to DR. The routers in the network will store the DR and BDR. The to DR. The routers in the network will store the DR and BDR. The
hello messages sent by all the routers are same with the value of DR hello messages sent by all the routers are same with the value of DR
and BDR are all set. and BDR are all set.
skipping to change at page 7, line 25 skipping to change at page 8, line 16
hello messages from other routers that the value of DR is set. The hello messages from other routers that the value of DR is set. The
new router will not change the existed DR even if it is superior to new router will not change the existed DR even if it is superior to
the existed DR. If the new router is superior to existed BDR, the the existed DR. If the new router is superior to existed BDR, the
new router will replace the existed BDR. new router will replace the existed BDR.
When the routers receive hello message from a new router, the routers When the routers receive hello message from a new router, the routers
will compare the new router and all the other routers on the LAN. If will compare the new router and all the other routers on the LAN. If
the new router is superior to existed BDR, the new router will be new the new router is superior to existed BDR, the new router will be new
BDR. Then the old BDR will send prune message to upstream routers. BDR. Then the old BDR will send prune message to upstream routers.
As a result, the BDR is the one who has the highest priority except As a result, the BDR is the one which has the highest priority except
DR. Once the DR is elected, the DR will not change until it fails. DR. Once the DR is elected, the DR will not change until it fails or
After the DR and BDR are elected, the routers in the network will manually adjustment. After the DR and BDR are elected, the routers
store the address of DR and BDR. in the network will store the address of DR and BDR.
5. Deployment suggestion 5. Compatibility
If the LAN is a hybrid network that there are some routers which have
DR/BDR capability and the other routers which have not DR/BDR
capability. In order to avoid duplicated multicast flows in the LAN,
all the routers should go backward to use the algorithm defined in
[RFC4601] and [RFC7761].
6. Deployment suggestion
If there are two and more routers on a share-media LAN, and the If there are two and more routers on a share-media LAN, and the
multicast services is sensitive to the lost of multicast packets, the multicast services is sensitive to the lost of multicast packets, the
function of DR and BDR defined in this document should be deployed. function of DR and BDR defined in this document should be deployed.
6. Security Considerations 7. Security Considerations
For general PIM Security Considerations. For general PIM Security Considerations.
7. IANA Considerations 8. IANA Considerations
IANA is requested to allocate OptionTypes in TLVs of hello message. IANA is requested to allocate OptionTypes in TLVs of hello message.
Include DR and BDR. Include DR and BDR.
8. Normative References 9. Normative References
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328,
DOI 10.17487/RFC2328, April 1998, DOI 10.17487/RFC2328, April 1998,
<http://www.rfc-editor.org/info/rfc2328>. <http://www.rfc-editor.org/info/rfc2328>.
[RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas, [RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas,
"Protocol Independent Multicast - Sparse Mode (PIM-SM): "Protocol Independent Multicast - Sparse Mode (PIM-SM):
Protocol Specification (Revised)", RFC 4601, Protocol Specification (Revised)", RFC 4601,
DOI 10.17487/RFC4601, August 2006, DOI 10.17487/RFC4601, August 2006,
<http://www.rfc-editor.org/info/rfc4601>. <http://www.rfc-editor.org/info/rfc4601>.
 End of changes. 22 change blocks. 
53 lines changed or deleted 101 lines changed or added

This html diff was produced by rfcdiff 1.45. The latest version is available from http://tools.ietf.org/tools/rfcdiff/