Internet DRAFT - draft-jacob-mpls-ethldp
draft-jacob-mpls-ethldp
Network Working Group Sudhin Jacob
Internet Draft Juniper Networks
Intended Status: Experimental
sep 15, 2015
Ethernet LDP( Label Distribution with out IP and routing protocols)
draft-jacob-mpls-ethldp-02.txt
Abstract
MPLS is the heart and soul of the service provider network. MPLS
can carry anydata payload which gives the flexibility to the service
provider to provision new service with any expense.The benefit of this
technology is core router need not understand the full customer route.
If the service a layer 2 then thereis no need of vrf, for customer the
service provider cloud is like a virtual switch.The protocol used for
label distribution is LDP, BGP,RSVP. The most popular protocol for
outer label distribution is LDP. LDP has the benefit of adding more TLV to
its payload. In this the possibility of using ldp for generating labels
for mac address rather for ip address which gives the benefit to service
provider not to run complex routing protocol on core, this does not require
ip address. This gives service provider the flexibility to deploy any services,
there is no need for changes in network layer when the customer goes for
ipv4 to ipv6. This can reduce the CAPEX and OPEX of the customer and reduces
the hardware cost too.
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Table of Contents
1.Introduction.....................................................3
2.Eth-ldp Problem Statement........................................4
3.How Eth-ldp will work............................................4
3.4 ETH-LDP for Customer Networks.................................7
3.5 ETH-LDP handling BUM from multihomed CE.......................8
3.5 ETH-LDP Split Horizon label,Load balancing label...............10
4.1. Normative References..........................................11
1.Introduction
The current technologies require ip address to establish a label advertising
protocol.This paper explains to have label adevertisement with out the ip address
and routing protocol.This saves the configuration ,provisioning and trobleshooting
time. In this there is no requirment of routing protocol to advertise the loopback
address of the routers infact this have the cpablity to generate label per interface
so this is very helpful in load balancing the traffic.Once this is configured on
interface it will pick up the interface mac address and it will start communicating
automatically with the help of interface mac address. Once the hello is exchanged between
the two routers the adjacencies are formed. Once the adjacency is established then
it can start exchange labels.The label mapping message will be exchanged to the
neighbor router, it will generate labels for its entire connected interfaces.
These labels will be generated for mac addresses instead of IP addresses.
The labels are generated for mac address instead of IP address there
will be changes in the normal ldp TLV.This can reduce the overall cost of operation
and maintenance. The benefit is we can extend the label switching to metro ring and
remove the complex configurations and vlan tagging.
2. Problem Statement
There are different transport mechansim to carry customer data which requires
IP address, Eth-LDP addresses the fact that the data from a layer 2 network
from one geographical location to another can be transported to another using mac
ldp which is simpler reduces the overhead to the Service provider and gives the customer
more flexiblity to control the network.
3.How ETH-LDP will work
Router A----------------------Router B------------------Router C
Example: 1
Consider three routers A, B and C the interfaces are connected. There are no
other protocols configured in these routers.Once we enable Ethernet LDP over
the interface, it sends hello message, once hello message is received from the neighbor
router both the routers receives from the neighbor router the adjacency is established.
Once the adjacency is established,it sends label mapping message with labels for the
connected interface and labels received from the other routers.Once the router gets
the label after processing it updates the LIB so the router A knows the label to reach
router C and vice versa. For example Router C advertise label 20 for its connected mac
address it sends to Router B and router B sends label 21 for its connected mac address
as well for the mac address of other routers reachable via router B to router A.
Router A sends label 23 for its connected interface to router B and the router B
sends label 24 to router C for its connected interface and mac address of other routers
reachable through B to router C.When the data packet arrives at router A destined to router B,
the label 21 is pushed by router A and send to router B.In router B the label swap
operation is performed, router B knows once it gets a packet with label 20 it has to swap
operation with label 21 and forwards the packet to to router C. The same operation
is performed when the return packet goes from router C to router A. Router C pushes label 24
sends to router B and it swaps label with 23 and sends it to A.
3.1 ETH-LDP Hellos and Adjacency formations
ETH-LDP Hello TLV
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version | PDU Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LDP Identifier |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Value |
~ ~
| |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Here the header will version will be 1; ldp identifier will be the mac address of the router or
configured ID for identifying the router.The hello TLV consist of hold timer,flags, etc the
transport address is removed from this because the communication is based on the mac address.
The router will send hello at the configured hold interval divided by 3. The router is not
receiving hello it will mark the neighbor down once the hold time is expired.
The adjacency is lost all the labels learned from the peer will be flushed.
The format of the hello message is same like ipv4 ldp but certain fields are modified to
carry out the operation. The hello message id is same 0x100.
3.2 ETH-LDP Label Advertisements
+-----------+ +------------+
| | | |
| | | |
| A |--------------------------- |
| | | B |
| | | |
+--|--------+ | |
| -- +-----|------+
| -- --- |
| -- --- |
| -- -- |
| -- --- |
| +---------------+ |
| | | |
| | | |
| | C | |
| | | |
| | | |
| +---------------+ |
| -- -- |
| --- -- |
| -- --- |
| --- -- |
| -- -- |
+---|--------------+ +-----------|----+
| | | |
| | | |
| D ---------------- |
| | | E |
| | | |
| | | |
+------------------+ +----------------+
Since we are not using routing protocol for label advertisements so routers dont have any
idea for preventing loops because for the same mac address it receives labels from multiple
sources. In order to avoid this scenario the label advertisement message must carry labels
along with hop count (distance) so the router receives multiple labels from routers it will
select only the lowest hop count (distance). It will not accept the labels for itself from others.
The label must be generated for per platform basis. For example Router D generates label for its
connected mac address to Router A and it advertises the same to router C and router B, router C
and B advertises about router D labels to router A along with hop count when router A compares
the labels received for router D mac address from Router B,D and C.Router A sees labels for reaching router D
is lowest from router D so it takes labels for destination in router D from router D because of its lowest
hop count. This prevents the loops. The other two details are cached in times of failure that can be used.
The behavior is different when there is multiple links from same router there remote mac address will
have multiple labels based on links and it will load balance based on different labels.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0|0| Hop Count | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| HC Value |
+-+-+-+-+-+-+-+-+
3.3 ETH-LDP Label Withdrawal
When the link is down the ETH-LDP sends a withdrawal message to withdraw the mac addess
and the label ascociated to it for the remote PE router.Then the label will be flushed
from the label database.
3.4 ETH-LDP for Customer Networks
The PE routers which are connected to service provider can converged using above mentioned
mechanism.When the customer wants to be connected the service provider msut know what all
edge routers the customer traffic must be dropped.
CE1--------PE1
--------------P---------------------PE2--------CE3
CE2---------PE1
Consider the above network customer A is multihomed and he wants to connect to remote
site located at PE2,the service provider will make a connection to remote PE2 from PE1
and viceversa from PE2 to PE1.Once that is done the PE1 will generate a labels for BUM
traffic,for unicast mac address,PE2 will generate the same for customer A. When the
traffic comes CE1 the PE1 will put the BUM label then PE1 will put the outer label
and forward the packet so once the packet reaches PE2 the label look up is done based on the
inner label the packet is put in the correct instances.
3.5 ETH-LDP handling BUM from multihomed CE
When the BUM traffic is orginated from one of the multihomed CE, it will not send the traffic
back based on split horizon.When it is multihoming to different PE,one of PE will be elected
as forwarder for this while configuring the PE's who all are in multihoming there must be
a TLV which shows it is multihoming.So PE's sends targetted ETH-LDP with multihoming flag set.
so based on the PE the PE with highest mac address is elected as DF, or there we can set priority
to select the DF so that we can control the forwarder election,the default priority is 1.
First it will check the highest priority, if there is a tie then it will select the highest mac address.
The DF will forward the BUM traffic. Once DF is elected it will send split horizon label to
other non DF router to send BUM traffic, if the BUM traffic is comming to non DF routers it will
drop the traffic.Once the BUM traffic is coming to DF with split horizon label it will drop that
traffic to avoid loops.the DF will send loadbalancing labels to all routers excpet the multihoming
PE's this way it will load balance the traffic.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0|0| Flags | priority |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| HC Value |
+-+-+-+-+-+-+-+-+
3.5 ETH-LDP Split Horizon label,Load balancing label
The above labels will be generated for multihoming PE's once the DF is elected, DF will send split
horizon label label to non DF's. This is used to prevent blocking BUM traffic sending back to
the multihomed site.Once the BUM traffic recieved from attached CE's to non DF PE's it will
use split horizon label to send it to DF PE's, it will add the BUM label,split horizon label
and outer label to reach to remote PE.Once it reaches the DF PE it sees the split horizon label,
it will drop the traffic.The load balancing label will be used to load balancing the traffic from remote
PE's to multihoming PE's. This labels will be advertised by DF to remote PE's so it will use to load balance
the traffic from remote PE to multihoming PE's
References
4.1. Normative References
[RFC5036] LDP Psecifications L. Andersson, Ed.
Author Addresses
Sudhin Jacob
Bangalore, India
Email:sjacob@juniper.net
Email: sudhinjacob@rediffmail.com
