Juniper JUNOSE 11.1.X - LINK LAYER CONFIGURATION 4-7-2010, Configuration Manual

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Application
Some users need more bandwidth than a T1 or an E1 channel can provide, but cannot
afford the expense or do not need the bandwidth of T3 or E3. Equal-cost multipath
(ECMP) is one way to achieve the desired bandwidth. MLPPP is commonly used as
an alternative to ECMP to deliver
NxT1 service. NxT1 service provides bandwidth
greater than DS1 service without going up to the expense and infrastructure required
for DS3 service. Cost-analysis of NxT1 versus DS3 service typically imposes a practical
limit of 8xT1 service; that is, aggregation of no more than eight T1 or E1 connections
into an MLPPP bundle.
The NxT1 implementation of MLPPP logically aggregates up to eight T1 or E1
connections into a single virtual connection, or bundle, to a given customer site, as
shown in Figure 35 on page 304.
Figure 35: MLPPP Aggregation of T1 Lines into a Single Bundle
Because MLPPP aggregates multiple link-layer channels onto a single network-layer
IP interface, protocol layering within the router is different than for non-multilink
PPP.
Figure 36 on page 304 illustrates interface stacking with MLPPP.
Figure 36: Structure of MLPPP
MLPPP LCP Extensions
Multilink PPP adds the following LCP negotiation options:
■
Multilink maximum received reconstructed unit (MRRU) option—The MRRU
option has two functions. First, it informs the other end of the link the maximum
size of the PPP packet payload that the router can receive. Second, it informs
304 ■
Overview
JUNOSe 11.1.x Link Layer Configuration Guide