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IPv4 Routing Protocols
The JUNOS Internet software implements full IP routing functionality,
providing support for IP version 4 (IPv4). The routing protocols are fully
interoperable with existing IP routing protocols and provide the scale and
control necessary for the Internet core. The software provides support for
the following routing and traffic engineering protocols:
- Unicast routing protocols
- BGP—Border Gateway Protocol, version 4, is an Exterior Gateway
Protocol (EGP) that guarantees loop-free exchange of routing information between
routing domains (also called autonomous systems). BGP, in conjunction with
JUNOS routing policy, provides a system of administrative checks and balances
that can be used to implement peering and transit agreements.
- ICMP—Internet Control Message Protocol router discovery
is a method that hosts can use to discover the addresses of operational routers
on a subnet.
- IS-IS—Intermediate System-to-Intermediate System is a link-state
interior gateway protocol (IGP) for IP networks that uses the shortest-path-first
algorithm (SPF algorithm, also called the Dijkstra algorithm) to determine
routes.
- OSPF—Open Shortest Path First, version 2, is an IGP developed
for IP networks by the Internet Engineering Task Force (IETF). OSPF is a link-state
protocol that makes routing decisions based on the SPF algorithm.
- RIP—Routing Information Protocol, version 2, is an IGP for
IP networks based on the Bellman-Ford algorithm. RIP is a distance-vector
protocol. RIP dynamically routes packets between a subscriber and a service
provider without the subscriber having to configure BGP or to participate
in the service provider’s IGP discovery process.
- Multicast routing protocols
- DVMRP—Distance Vector Multicast Routing Protocol is a dense-mode
(flood-and-prune) multicast routing protocol.
- IGMP—Internet Group Management Protocol, versions 1 and
2, is used to manage membership in multicast groups.
- MSDP—Multicast Source Discovery Protocol enables multiple
PIM sparse mode domains to be joined. A rendezvous point (RP) in a PIM sparse
mode domain has a peering relationship with an RP in another domain, thereby
discovering multicast sources from other domains.
- PIM sparse mode and dense mode—Protocol-Independent Multicast
is a multicast routing protocol used to route traffic to multicast groups
that might span wide-area and interdomain internetworks. In PIM sparse mode,
routers explicitly join and leave multicast groups. PIM dense mode is a flood-and-prune
protocol.
- SAP/SDP—Session Announcement Protocol and Session Description
Protocol handle conference session announcements.
- MPLS application protocols
- LDP—Label Distribution Protocol provides a mechanism for
distributing labels in nontraffic-engineered applications. LDP allows routers
to establish label-switched paths (LSPs) through a network by mapping network-layer
routing information directly to data-link layer switched paths. LSPs created
by LDP can also traverse LSPs created by Resource Reservation Protocol (RSVP).
- MPLS—Multiprotocol Label Switching enables you to configure
LSPs through a network either manually or dynamically. You can control how
traffic traverses the network by directing it through particular paths, rather
than relying on an IGP's least-cost algorithm to choose a path.
- RSVP—Resource Reservation Protocol, version 1, provides
a mechanism for engineering network traffic patterns that is independent of
the shortest path determined by a routing protocol. RSVP itself is not a routing
protocol, but is designed to operate with current and future unicast and multicast
routing protocols. JUNOS RSVP software supports dynamic signaling for MPLS
LSPs.
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