Juniper JUNOSE 11.1.X - LINK LAYER CONFIGURATION 4-7-2010, Руководство по настройке

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E Series routers support the following AAL5 encapsulation types as specified in RFC
2684—Multiprotocol Encapsulation over ATM Adaptation Layer 5 (September 1999),
which replaces RFC 1483:
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aal5snap—LLC/SNAP
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aal5mux ip—VC-based multiplexing
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aal5autoconfig—LLC/SNAP or VC-based multiplexing. (See “Configuring Dynamic
Interfaces” on page 515.)
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aal5all—Martini encapsulation
NOTE: The Juniper Networks E120 and E320 Broadband Services Routers do not
support Martini encapsulation (aal5all) in the current release.
Local ATM Passthrough
E Series routers support local ATM passthrough for ATM layer 2 services over
Multiprotocol Label Switching (MPLS). Local ATM passthrough enables the router to
emulate packet-based ATM switching. The ATM passthrough feature is useful for
customers who run IP in most of their network but still have to carry a small amount
of native ATM traffic.
Local ATM passthrough uses ATM Martini encapsulation to emulate ATM switch
behavior. You can create pairs of cross-connected ATM VCs within the router. The
router then passes AAL5 traffic between two VCs, regardless of the contents of the
packets.
You can also use AAL0 encapsulation when you configure a local ATM passthrough
connection. AAL0 encapsulation causes the router to receive raw ATM cells on this
circuit and to forward the cells without performing AAL5 packet reassembly.
For more information, see chapter Configuring Layer 2 Services over MPLS in JUNOSe
BGP and MPLS Configuration Guide .
VCC Cell Relay Encapsulation
E Series routers support virtual channel connection (VCC) cell relay encapsulation
for ATM layer 2 services over MPLS. VCC cell relay encapsulation is useful for
voice-over-ATM applications that use AAL2-encapsulated voice transmission.
VCC cell relay encapsulation enables the router to emulate ATM switch behavior by
forwarding individual ATM cells over an MPLS pseudowire (also referred to as an
MPLS tunnel) created between two ATM VCCs, or as part of a local ATM passthrough
connection between two ATM 1483 subinterfaces on the same router. The E Series
implementation conforms to the required N-to-1 cell mode encapsulation method
described in the Martini draft, Encapsulation Methods for Transport of ATM Over
MPLS Networks—draft-ietf-pwe3-atm-encap-07.txt (April 2005 expiration), with the
provision that only a single ATM virtual circuit (VC) can be mapped to an MPLS tunnel.
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Overview
JUNOSe 11.1.x Link Layer Configuration Guide