MPLS
RSVP – OAM BFD
1. Intro We can configure OAM BFD for LSPs to detect LSP data plane faults. To bootstrap the OAM BFD session, there is an initial exchange of MPLS Ping packets (Echo Request/Reply) between the ingress and egress routers, that is using UDP port 3503. After the initial MPLS Ping exchange, the routers will exchange BFD […]
RSVP – soft-preemption/adaptive
1. Intro Essentially, we are discussing here about the make before break (MBB) feature. You will see MBB is enabled by default for some features, like periodic re-optimization of LSPs. By default, MBB is disabled for LSP preemption, but we can change this with either soft-preemption or adaptive. Soft preemption attempts to establish a new path for […]
RSVP – Link/Node Protection
1. Intro The Junos implementation of facility backup is link protection. This feature is interface based rather than LSP based. Whereas fast reroute is trying to protect the whole LSP (1:1 protection), link protection (1:n) protects only the link, however, it can protect multiple LSPs. A bypass LSP must terminate on the downstream LSR. Bypass […]
RSVP – fast reroute
1. Intro Fast reroute can dramatically reduce packet loss in the case a primary path fails. Even if you have a secondary path signaled with the standby feature there is still the possibility of many packet drops. This happens because the message for the failed path must still travel back towards the ingress LSR so […]
RSVP – Secondary Paths
1. Intro In the previous example we tested link coloring with multiple LSPs to the same destination, which is not ideal. In this post we will configure Secondary paths. By default, when network failures occur along the path of RSVP signaled LSPs, traffic will be dropped. The ingress LSR continues to send traffic until a […]
RSVP – Link Coloring
1. Intro Administrative groups provide the ability to mark the interfaces with similar characteristics in a common group. Based on these groups you can restrict the LSPs to use a certain path in the network. Marking the interfaces is known as coloring but is actually based on setting the affinity bits on interfaces. Up to […]
LDP deaggregate
When an LDP egress router advertises multiple prefixes, the prefixes are bound to a single label and aggregated into a single forwarding equivalence class (FEC). By default, LDP maintains this aggregation as the advertisement traverses the network. On a random PE, we can see how multiple prefixes are bound to one single label: Apply the […]
LDP track-igp-metric
1. Intro In this post we will demonstrate the impact of LDP track-igp-metric. The setup is the one from the diagram below, where R1 receives the 3.3.3.0/24 prefix via BGP from R9 and R6. Depending on whether track-igp-metric command is configured or not, R1 will prefer either R9 or R6 to reach 3.3.3.0/24. 2. Initial […]
LDP Synchronization
1. Intro In this post we will look at the LDP Synchronization feature, and the impact it can create in the network. We will work with the following setup, where between R1 and R3, the LDP protocols was not activated in the configuration the R1 router. Because of this, the IGP protocol (OSPF in this […]
RSVP – Basic Config
1. Intro We will use the following test topology for RSVP: For RSVP basic configuration we need to perform the following: 2. RSVP Basic Configuration We we will demonstrate RSVP basic config on R1 router (all other routers already configured): External Resouces: