Cisco ASR 9000 Series Routing Configuration Guide

•
Disable TCP MSS for a particular neighbor in the neighbor group or session group using the
inheritance-disable command.
•
Unconfigure TCP MSS value. On unconfiguration, TCP MSS value in the protocol control block (PCB)
is set to the default value.
The default TCP MSS value is 536 (in octets) or 1460 (in bytes). The MSS default of
1460 means that TCP segments the data in the transmit queue into 1460-byte chunks
before passing the packets to the IP layer.
Note
To configure per neighbor TCP MSS, use the tcp mss command under per neighbor, neighbor group or session
group configuration.
For detailed configuration steps, see Configuring Per Neighbor TCP MSS, on page 93.
For detailed steps to disable per neighbor TCP MSS, see Disabling Per Neighbor TCP MSS, on page 95.
MPLS VPN Carrier Supporting Carrier
Carrier supporting carrier (CSC) is a term used to describe a situation in which one service provider allows
another service provider to use a segment of its backbone network. The service provider that provides the
segment of the backbone network to the other provider is called the backbone carrier. The service provider
that uses the segment of the backbone network is called the customer carrier.
A backbone carrier offers Border Gateway Protocol and Multiprotocol Label Switching (BGP/MPLS) VPN
services. The customer carrier can be either:
•
An Internet service provider (ISP) (By definition, an ISP does not provide VPN service.)
•
A BGP/MPLS VPN service provider
You can configure a CSC network to enable BGP to transport routes and MPLS labels between the backbone
carrier provider edge (PE) routers and the customer carrier customer edge (CE) routers using multiple paths.
The benefits of using BGP to distribute IPv4 routes and MPLS label routes are:
•
BGP takes the place of an Interior Gateway Protocol (IGP) and Label Distribution Protocol (LDP) in a
VPN routing and forwarding (VRF) table. You can use BGP to distribute routes and MPLS labels. Using
a single protocol instead of two simplifies the configuration and troubleshooting.
•
BGP is the preferred routing protocol for connecting two ISPs, mainly because of its routing policies
and ability to scale. ISPs commonly use BGP between two providers. This feature enables those ISPs
to use BGP.
For detailed information on configuring MPLS VPN CSC with BGP, see the Implementing MPLS Layer 3
VPNs on Cisco ASR 9000 Series Router module of the Cisco ASR 9000 Series Aggregation Services Router
MPLS Configuration Guide.
Cisco ASR 9000 Series Aggregation Services Router Routing Configuration Guide, Release 5.3.x
53
Implementing BGP
MPLS VPN Carrier Supporting Carrier

Cisco ASR 9000 Series Specifications

General

Brand	Cisco
Model	ASR 9000 Series
Category	Network Router
Language	English